An adult male cheetah's total size can measure from 168 to 200 cm (66 to 79 in) and 162 to 213 cm (64 to 84 in) for females. Adult cheetahs are 70 to 90 cm (28 to 35 in) tall at the shoulder. Males are slightly taller than females and have slightly bigger heads with wider incisors and longer mandibles.

The Pokhot live in the Baringo and Western Pokot districts of Kenya and in Uganda.

There are two main sub-groups depending of their location and way of life. The first group consist of the Hill Pokot who live in the rainy highlands in the west and in the central south, and are mainly farmers and pastoralists. The second group is made up of the Plains Pokot who live in dry and infertile plains, with their cattles. A homestead is composed of one or more buildings for a man, his wife and children; eventual co-wives live in separate houses. The role of the community in teaching children ethical rules. Most of the Pokot are nomadic and thus have interacted with different peoples, incorporating their social customs.The Pokot are very proud of their culture. The Songs, storytelling, and decorative arts, especially bodily decoration, are very appreciated. They adorn the body with beads, hairstyling, scarification, and the removal of the lower central incisors. Pokot girls wear a beaded necklace made of the stems of an asparagus tree. Most Pokot have some knowledge of herbal medicine, so they often use these treatments along with those of the hospitals. They belong to the Kenya's Nilotic-speaking peoples. .

For the Pokot, the universe has two realms: the above is the realm of the most powerful deities—Tororot, Asis (sun), and llat (rain); and the below is the one where live humans, animals, and plants. Humans are responsible for the realm that they inhabit, but they rely upon divinities to achieve and maintain peace and prosperity. They worship many deities like the sun, moon and believe in the spirit of death.The Pokot communicate with their deities through prayer and sacrifice. They perform it during ethnic festivals and dances. Oracles are responsible for maintaining the spiritual balance within the community. They are superstitious and believe in sorcery, so sometimes they call on shielding lucky sorcery. They have prophets, either male or female, who foresee advise, usually by the means of animal sacrifices. His or her ability is considered as a divine gift. Clan histories recount the changes of location, through poetry and song, emphasizing the vulnerability of humans and the importance of supernatural powers to help them overcome hunger, thirst, and even death. Ceremonies mark the transitions in the people's social lives. Among these are: the cleansing of a couple expecting their first child; the cleansing of newborn infants and their mothers; the cleansing of twins and other children who are born under unusual circumstances; male and female initiation; marriage; sapana, a coming-of-age ceremony for men; and summer-solstice, harvest, and healing ceremonies. The most important rite of passage for most Pokot is circumcision for boys and clitoridectomy for girls. These rites consist of a series of neighborhood-based ceremonies, emphasizing the importance of having a good behavior. When boys are circumcised, they acquire membership in one of eight age sets. Women do not have age-sets. After excisions, for several months, girls have a white painting on their face and wear a hood made of blackened leather with charcoal and oil. This means they are untouchable until the lepan ceremony, that marks the passage to womanhood. Unlike other tribes, the Pokot keep the affiliation to their clan throughout their lives, there is no disruption with marriage. Surprisingly, the agreement before marriage is made by gift giving, from the groom and his family to the bride and her family, often over a period of years (and not the contrary). It often implies the gift of a combination of livestock, goods, and cash to the bride's family, and the allotment of milk cows and rights to land to the bride. The bond between a husband and wife lasts for 3 generations, after what marriages can take place again between the two groups. Polygamy exists but is not prevalent among men before 40. The spirits of the elder anticipate reincarnation in their living descendants: when a child is said to resemble the elder, the same name is given. Disputes are resolved in neighborhood councils and in government courts. Some of the sanctions include shaming, cursing, and bewitching.

  

© Eric Lafforgue

www.ericlafforgue.com

 

The bank vole manages to run with the large hazelnut in its mouth, gripping the rough end with its incisors. The hazelnuts is however often dropped (especially when diving into a tunnel), and sometimes abandoned, before reaching the final destination.

 

Here the vole has stopped momentarily before traversing one of several relatively open stretches on the way. Sometimes the vole turns around a chooses another path.

In most of the tribes in Kenya, men use this wodden pillow/ seat.

The Pokhot live in the Baringo and Western Pokot districts of Kenya and in Uganda.

There are two main sub-groups depending of their location and way of life. The first group consist of the Hill Pokot who live in the rainy highlands in the west and in the central south, and are mainly farmers and pastoralists. The second group is made up of the Plains Pokot who live in dry and infertile plains, with their cattles. A homestead is composed of one or more buildings for a man, his wife and children; eventual co-wives live in separate houses. The role of the community in teaching children ethical rules. Most of the Pokot are nomadic and thus have interacted with different peoples, incorporating their social customs.The Pokot are very proud of their culture. The Songs, storytelling, and decorative arts, especially bodily decoration, are very appreciated. They adorn the body with beads, hairstyling, scarification, and the removal of the lower central incisors. Pokot girls wear a beaded necklace made of the stems of an asparagus tree. Most Pokot have some knowledge of herbal medicine, so they often use these treatments along with those of the hospitals. They belong to the Kenya's Nilotic-speaking peoples. .

For the Pokot, the universe has two realms: the above is the realm of the most powerful deities—Tororot, Asis (sun), and llat (rain); and the below is the one where live humans, animals, and plants. Humans are responsible for the realm that they inhabit, but they rely upon divinities to achieve and maintain peace and prosperity. They worship many deities like the sun, moon and believe in the spirit of death.The Pokot communicate with their deities through prayer and sacrifice. They perform it during ethnic festivals and dances. Oracles are responsible for maintaining the spiritual balance within the community. They are superstitious and believe in sorcery, so sometimes they call on shielding lucky sorcery. They have prophets, either male or female, who foresee advise, usually by the means of animal sacrifices. His or her ability is considered as a divine gift. Clan histories recount the changes of location, through poetry and song, emphasizing the vulnerability of humans and the importance of supernatural powers to help them overcome hunger, thirst, and even death. Ceremonies mark the transitions in the people's social lives. Among these are: the cleansing of a couple expecting their first child; the cleansing of newborn infants and their mothers; the cleansing of twins and other children who are born under unusual circumstances; male and female initiation; marriage; sapana, a coming-of-age ceremony for men; and summer-solstice, harvest, and healing ceremonies. The most important rite of passage for most Pokot is circumcision for boys and clitoridectomy for girls. These rites consist of a series of neighborhood-based ceremonies, emphasizing the importance of having a good behavior. When boys are circumcised, they acquire membership in one of eight age sets. Women do not have age-sets. After excisions, for several months, girls have a white painting on their face and wear a hood made of blackened leather with charcoal and oil. This means they are untouchable until the lepan ceremony, that marks the passage to womanhood. Unlike other tribes, the Pokot keep the affiliation to their clan throughout their lives, there is no disruption with marriage. Surprisingly, the agreement before marriage is made by gift giving, from the groom and his family to the bride and her family, often over a period of years (and not the contrary). It often implies the gift of a combination of livestock, goods, and cash to the bride's family, and the allotment of milk cows and rights to land to the bride. The bond between a husband and wife lasts for 3 generations, after what marriages can take place again between the two groups. Polygamy exists but is not prevalent among men before 40. The spirits of the elder anticipate reincarnation in their living descendants: when a child is said to resemble the elder, the same name is given. Disputes are resolved in neighborhood councils and in government courts. Some of the sanctions include shaming, cursing, and bewitching.

 

© Eric Lafforgue

www.ericlafforgue.com

    

3D Print: Idaho Virtualization Laboratory sculpt.

Idaho Museum of Natural History, ISU, Pocatello, Idaho

28 September 2020

 

"Gorgonopsia (from the Ancient Greek γοργών, meaning "gorgon", and ὄψ, meaning "aspect") is an extinct clade of early sabre-toothed therapsids from the Middle to Upper Permian. They are characterised by a long and narrow skull, as well as engorged upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhaust it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an incredible gape, possibly in excess of 90°, without having to unhinge the jaw." - Wikipedia

Fotografados na Imprensa Nacional - IN, em Brasília-DF, Brasil.

 

Um sagui[1][2] (do tupi sauín), soim ou mico são as designações comuns dadas a várias espécies de pequenos macacos pertencentes à família Callitrichidae. A palavra sagui tem origem no tupi e sua pronúncia é feita observando-se o som da vogal "u".

Estes primatas são representados por várias espécies em território brasileiro. Todos os quais possuem o dedo polegar da mão muito curto e não oponível, as unhas em forma de garras, e dentes molares de fórmula 2/2. São espécies de pequeno porte e de cauda longa.

São os menores símios do mundo, estão dispersos por toda a América do Sul e vivem geralmente em bandos que se hospedam em árvores, como os esquilos. Travessos e ágeis, movem-se em saltos bruscos, emitindo guinchos e assobios que são ouvidos de longe.

 

Sagui-de-tufos-brancos

Espécies

 

Família Callitrichidae

Callithrix jacchus - Sagui-de-tufos-brancos

Callithrix penicillata - Sagui-de-tufos-pretos

Callithrix kuhlii - Sagui-de-wied

Callithrix geoffroyi - Sagui-de-cara-branca

Callithrix flaviceps - Sagui-da-serra

Callithrix aurita - Sagui-da-serra-escuro

Callithrix argentata - Sagui-branco

Callithrix nigriceps - Sagui-de-cabeça-preta

Callithrix humeralifera - Sagui-de-santarém

Saguinus fuscicollis - Sagui-de-cara-suja

Saguinus imperator - Sagui-imperador

Saguinus labiatus - Sagui-de-bigode

Saguinus mystax - Sagui-de-boca-branca

Saguinus oedipus - Sagui-de-cabeça-branca

Saguinus bicolor - Sagui-de-coleira

Família Callimiconidae

Callimico goeldi - Sagui-goeldi

Referências

 

↑ michaelis.uol.com.br/moderno/portugues/index.php?lingua=p...

↑ Desde 1 de janeiro de 2009, em virtude da vigência do Acordo Ortográfico de 1990, a palavra não é mais grafada com trema (sagüi).

  

O sagüi (português brasileiro) ou sagui (português europeu) (AO 1990: sagui), soim, mico, marmoset (em inglês) ou tamarim (em inglês) são as designações comuns dadas a várias espécies de pequenos macacos pertencentes à família Callitrichidae.

Estes primatas são representados por várias espécies em território brasileiro. Todos os quais possuem o dedo polegar da mão muito curto e não oponível, as unhas em forma de garras, e dentes molares de fórmula 2/2. São espécies de pequeno porte e de cauda longa.

São os menores símios do mundo, estão dispersos por toda a América do Sul e vivem geralmente em bandos que se hospedam, como os esquilos em árvores. Travessos e ágeis, movem-se a saltos bruscos, emitindo guinchos e assobios que são ouvidos de longe.

  

Projetos do Parque Burle Marx - Brasília

 

Um novo espaço de conservação ambiental, diversão e lazer estará, em breve, à disposição da população de Brasília. É o Parque Burle Marx, com cerca de 3 milhões de metros quadrados, entre o local onde será construído o Setor Habitacional Noroeste e a Asa Norte, no Plano Piloto de Brasília. No momento, são desenvolvidos pela Topocart os projetos executivos de urbanismo, paisagismo e infraestrutura do novo espaço, concebido para compensar o impacto ambiental que será causado pela implantação do novo empreendimento imobiliário.

 

No início deste ano, o Instituto Brasília Ambiental (Ibram) aprovou o Plano de Manejo elaborado pela Topocart para a Unidade de Conservação e alterou a classificação de Parque Ecológico para Parque de Uso Múltiplo. Essa mudança, segundo a coordenadora do Departamento de Arquitetura, Urbanismo e Meio Ambiente da Topocart, Janaina Vieira, possibilita maior flexibilidade na ocupação do espaço sem comprometer a preservação do meio ambiente e ainda contribui para acelerar a elaboração dos projetos que serão desenvolvidos no local.

 

De acordo com a arquiteta urbanista da Topocart, Carolina Favilla, o parque é uma das condicionantes para obtenção do licenciamento ambiental para a implantação do Setor Habitacional Noroeste. “Graças ao Parque, com suas quatro lagoas de retenção e detenção, foi possível resolver a questão da drenagem pluvial da região”, explica.

 

Praças e oásis

 

O estudo preliminar de urbanismo do Parque Burle Marx foi elaborado pelo escritório Jaime Lerner e é composto por um eixo central que interliga os diversos espaços de lazer. Entre as atrações do Parque se destacam a Praça das Sombras, junto a uma das entradas, os espaços Brennand e Krajberg - com exposição permanente de obras ao ar livre desses artistas plásticos, o Jardim Burle Marx, um museu interativo chamado de Planetário Indígena e o Museu Vivo do Cerrado. Intercalando cada uma dessas estruturas, ao longo do eixo central, serão erguidos espaços menores, batizados de oásis, com opções de recreação, gastronomia, exposições e descanso assistido.

 

Umas principais atrações do Parque será a Praça “Viva o Povo Brasileiro”, que ocupará um espaço de 90 mil metros quadrados destinados a atividades diversificadas que serão desenvolvidas ao redor de uma reprodução do mapa do Brasil em escala reduzida, refletindo fielmente o relevo e cercado por um espelho d’água representando o oceano Atlântico. De acordo com a arquiteta Giannina Picado Maykall, que coordena o desenvolvimento do projeto de implantação do Parque na Topocart, muitas dessas idéias foram incorporadas e desenvolvidas a partir do estudo preliminar elaborado pelo escritório Jaime Lerner. “Além de contemplar aspectos de lazer e meio ambiente, a criação do Parque Burle Marx proporciona soluções viárias para o tráfego da região”, ressalta.

 

Sustentabilidade

 

O Parque terá ainda quatro lagoas e uma zona de preservação, onde, possivelmente, será erguida a Escola de Preservação Ambiental de Brasília. Já a faixa que compreende todo o perímetro do empreendimento foi definida como de uso múltiplo e deve abrigar variadas estruturas voltadas para atividades cotidianas dos usuários residentes nas imediações do novo espaço.

 

Tanto a Escola Ambiental de Brasília, quanto o prédio que abrigará a Administração do Parque Burle Marx apresentam, como diferencial, os projetos concebidos de acordo com um conceito contemporâneo de sustentabilidade. Eles foram desenvolvidos pelo arquiteto da Topocart, Jandson Queiroz, a partir de uma abordagem que incorpora tecnologias de reaproveitamento da água e economia energética por meio de dispositivos como tetos verdes, orientação solar e a utilização de materiais reciclados.

 

Following, a text, in english, from Wikipedia the free encyclopédia:

 

Black-tufted marmoset, Photographed at Imprensa Nacional - IN, Brasília, DF, Brazil.

 

The black-tufted marmoset (Callithrix penicillata), also known as Mico-estrela in Portuguese, is a species of New World monkey that lives primarily in the Neo-tropical gallery forests of the Brazilian Central Plateau. It ranges from Bahia to Paraná,[3] and as far inland as Goiás, between 14 and 25 degrees south of the equator. This marmoset typically resides in rainforests, living an arboreal life high in the trees, but below the canopy. They are only rarely spotted near the ground.

Physical description:

The black-tufted marmoset is characterized by black tufts of hair around their ears. It typically has some sparse white hairs on its face. It usually has a brown or black head and its limbs and upper body are gray, as well as its abdomen, while its rump and underside are usually black. Its tail is ringed with black and white and is not prehensile, but is used for balance. It does not have an opposable thumb and its nails tend to have a claw-like appearance. The black-tufted marmoset reaches a size of 19 to 22 cm and weighs up to 350 g.

Behavior:

Diurnal and arboreal, the black-tufted marmoset has a lifestyle very similar to other marmosets. It typically lives in family groups of 2 to 14. The groups usually consist of a reproductive couple and their offspring. Twins are very common among this species and the males, as well as juvenile offspring, often assist the female in the raising of the young.

Though the black-tufted marmoset lives in small family groups, it is believed that they share their food source, sap trees, with other marmoset groups. Scent marking does occur within these groups, but it is believed that the marking is to deter other species rather than other black-tufted marmoset groups, because other groups typically ignore these markings. They also appear to be migratory, often moving in relation to the wet or dry seasons, however, the extent of their migration is unknown.

Though communication between black-tufted marmosets has not been studied thoroughly, it is believed that it communicates through vocalizations. It has known predator-specific cries and appears to vocalize frequently outside of predator cries.

Food and predation:

The Black-tufted Marmoset diet consists primarily of tree sap which it gets by nibbling the bark with its long lower incisors. In periods of drought, it will also include fruit and insects in its diet. In periods of serious drought it has also been known to eat small arthropods, molluscs, bird eggs, baby birds and small vertebrates.

Large birds of prey are the greatest threat to the black-tufted marmoset, however, snakes and wild cats also pose a danger to them. Predator-specific vocalizations and visual scanning are its only anti-predation techniques.

Reproduction:

The black-tufted marmoset is monogamous and lives in family groups. It reproduces twice a year, producing 1 to 4 offspring, though most often just twins. Its gestation period is 150 days and offspring are weaned after 8 weeks. There is considerable parental investment by this species, with both parents, as well as older juveniles, helping to raise the young. The offspring are extremely dependent on their parents and though they are sexually mature at 18 months, they typically do not mate until much later, staying with their family group until they do.

Ecosystem roles and conservation status:

The black-tufted marmoset is a mutualist with many species of fruit trees because it distributes the seeds from the fruit it consumes throughout the forests. However, it is a parasite on other species of trees because it creates sores in trees in order to extract sap, while offering no apparent benefit to the trees. Though this marmoset is not a main food source to any specific species, it is a food source to a number of different species, specifically large birds of prey, wild cats, and snakes.

While there are no known negative effects of marmosets towards humans, it carries specific positive effects by being a highly valuable exotic pet. It is also used in zoo exhibits and scientific research.

The black-tufted marmoset is listed as having no special status on the IUCN Red List or the United States Endangered Species Act List. It is listed in Appendix II of CITES and is not currently considered an endangered or threatened species.

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Infraclass: Eutheria

Order: Eulipotyphla

Family: Soricidae

A shrew or shrew mouse (family Soricidae) is a small mole-like mammal classified in the order Eulipotyphla. True shrews are also not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews, which belong to different families or orders.

 

Although its external appearance is generally that of a long-nosed mouse, a shrew is not a rodent, as mice are. It is in fact a much closer relative of moles, and related to rodents only in that both belong to the Boreoeutheria Magnorder. Shrews have sharp, spike-like teeth, not the familiar gnawing front incisor teeth of rodents.

 

Shrews are distributed almost worldwide: of the major tropical and temperate land masses, only New Guinea, Australia, and New Zealand do not have any native shrews; in South America, shrews are relatively recent immigrants and are present only in the northern Andes. In terms of species diversity, the shrew family is the fourth most successful mammal family, being rivalled only by the muroid rodent families Muridae and Cricetidae and the bat family Vespertilionidae.

Characteristics

 

All shrews are comparatively small, most no larger than a mouse. The largest species is the Asian house shrew (Suncus murinus) of tropical Asia, which is about 15 cm long and weighs around 100 g; several are very small, notably the Etruscan shrew (Suncus etruscus), which at about 3.5 cm (1.4 in) and 2 g (0.071 oz) is the smallest living terrestrial mammal.

 

In general, shrews are terrestrial creatures that forage for seeds, insects, nuts, worms, and a variety of other foods in leaf litter and dense vegetation, but some specialise in climbing trees, living underground, living under snow, or even hunting in water. They have small eyes and generally poor vision, but have excellent senses of hearing and smell.[3] They are very active animals, with voracious appetites. Shrews have unusually high metabolic rates, above that expected in comparable small mammals. Shrews in captivity can eat 1/2 to 2 times their own body weight in food daily.

 

They do not hibernate, but are capable of entering torpor. In winter, many species undergo morphological changes that drastically reduce their body weight. Shrews can lose between 30% and 50% of their body weight, shrinking the size of bones, skull, and internal organs.

 

Whereas rodents have gnawing incisors that grow throughout life, the teeth of shrews wear down throughout life, a problem made more extreme because they lose their milk teeth before birth, so have only one set of teeth throughout their lifetimes. Apart from the first pair of incisors, which are long and sharp, and the chewing molars at the back of the mouth, the teeth of shrews are small and peg-like, and may be reduced in number. The dental formula of shrews is:

3.1.1-3.3

 

1-2.0-1.1.3

 

Shrews are fiercely territorial, driving off rivals, and only coming together to mate. Many species dig burrows for caching food and hiding from predators, although this is not universal.

 

Female shrews can have up to 10 litters a year; in the tropics, they breed all year round; in temperate zones, they only stop breeding in the winter. Shrews have gestation periods of 17–32 days. The female often becomes pregnant within a day or so of giving birth, and lactates during her pregnancy, weaning one litter as the next is born.] Shrews live 12 to 30 months.

 

Shrews are unusual among mammals in a number of respects. Unlike most mammals, some species of shrews are venomous. Shrew venom is not conducted into the wound by fangs, but by grooves in the teeth. The venom contains various compounds, and the contents of the venom glands of the American short-tailed shrew are sufficient to kill 200 mice by intravenous injection. One chemical extracted from shrew venom may be potentially useful in the treatment of high blood pressure, while another compound may be useful in the treatment of some neuromuscular diseases and migraines.[8] The saliva of the northern short-tailed shrew (Blarina brevicauda) contains soricidin, a peptide which has been studied for use in treating ovarian cancer.[9] Also, along with the bats and toothed whales, some species of shrews use echolocation. Unlike most other mammals, shrews lack zygomatic bones (also called the jugals), so have incomplete zygomatic arches.

 

Echolocation

The northern short-tailed shrew is known to echolocate.

The only terrestrial mammals known to echolocate are two genera (Sorex and Blarina) of shrews, the tenrecs of Madagascar, and the solenodons.[citation needed] These include the Eurasian or common shrew (Sorex araneus) and the American vagrant shrew (Sorex vagrans) and northern short-tailed shrew (Blarina brevicauda). These shrews emit series of ultrasonic squeaks. The nature of shrew sounds, unlike those of bats, are low-amplitude, broadband, multiharmonic, and frequency modulated. They contain no "echolocation clicks" with reverberations and would seem to be used for simple, close-range spatial orientation. In contrast to bats, shrews use echolocation only to investigate their habitats rather than additionally to pinpoint food.

Except for large and thus strongly reflecting objects, such as a big stone or tree trunk, they probably are not able to disentangle echo scenes, but rather derive information on habitat type from the overall call reverberations. This might be comparable to human hearing whether one calls into a beech forest or into a reverberant wine cellar.

   

The common marmoset (Callithrix Jacchus) is classed as a New World monkey. It originally lived on the North-eastern coast of Brazil; however release of captive individuals has expanded its range to include Southeast Brazil. They are very small monkeys with relatively long tails. Males have an average height of 188 mm (7.40 in) and females have an average height of 185 mm (7.28 in). Males weigh 256 g (9.03 oz) on average and females weigh 236 g (8.32 oz) on average.

The common marmosets have claw-like nails on most of their fingers, with only their big toes having the flat nails that most other primates have. These nails, the shape of their incisors, and their specialist gut help their unique diet of gum, sap, latex and resins. They use their nails to cling to the side of a tree and, with their long lower incisors, chew a hole in the tree bark. They will then lick up the exudates.

Above information taken from Wikipedia.

You can see this typical feeding behaviour, as well as see them catching and eating insects and the occasional small bird, when visiting these marmosets at Longleat. They also enjoy the meal worms and sweet corn that the handlers use as treats to tempt them out into the viewing enclosure.

 

Ethiopian government is taking over and inciting girls to give up tribal customs such as scarification and lip plates. Without labret, a girl will be sold less for wedding (25 cows + 1 kalaschnikov)

Surma woman with her giant lip plate, a sign of beauty in Surma tribe, like in Mursi one. When they are ready to marry, they start to make a hole in the lip with a wood stick.

It will be kept for one night , and is removed to put a bigger one. This is very painful at this time... Few months after, the lip plate has its full size, and the girl is seen as beautiful by the men.

The lip plate made of wood or terracotta, and they have to remove the lower incisors to let some space for the disc. it's amazing to see them speak without any trouble, put it and remove it as a classic jewel.

Sometimes the lip is broken by the pressure of the lip plate. This is a very big problem for the girl cos men will consider her as ugly, she won't be able to marry anyone in the tribe apart the old men or the sick people...

The women are shaved, like the men, cos they hate hairiness!

 

© Eric Lafforgue

www.ericlafforgue.com

The wild boar (Sus scrofa), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The species is now one of the widest-ranging mammals in the world, as well as the most widespread suiform. It has been assessed as least concern on the IUCN Red List due to its wide range, high numbers, and adaptability to a diversity of habitats. It has become an invasive species in part of its introduced range. Wild boars probably originated in Southeast Asia during the Early Pleistocene and outcompeted other suid species as they spread throughout the Old World.

 

As of 2005, up to 16 subspecies are recognized, which are divided into four regional groupings based on skull height and lacrimal bone length. The species lives in matriarchal societies consisting of interrelated females and their young (both male and female). Fully grown males are usually solitary outside the breeding season. The wolf is the wild boar's main predator in most of its natural range except in the Far East and the Lesser Sunda Islands, where it is replaced by the tiger and Komodo dragon respectively. The wild boar has a long history of association with humans, having been the ancestor of most domestic pig breeds and a big-game animal for millennia. Boars have also re-hybridized in recent decades with feral pigs; these boar–pig hybrids have become a serious pest wild animal in the Americas and Australia.

 

Terminology

As true wild boars became extinct in Great Britain before the development of Modern English, the same terms are often used for both true wild boar and pigs, especially large or semi-wild ones. The English boar stems from the Old English bār, which is thought to be derived from the West Germanic bair, of unknown origin. Boar is sometimes used specifically to refer to males, and may also be used to refer to male domesticated pigs, especially breeding males that have not been castrated.

 

Sow, the traditional name for a female, again comes from Old English and Germanic; it stems from Proto-Indo-European, and is related to the Latin: sus and Greek hus, and more closely to the New High German Sau. The young may be called piglets or boarlets.

 

The animals' specific name scrofa is Latin for 'sow'.

 

Taxonomy and evolution

MtDNA studies indicate that the wild boar originated from islands in Southeast Asia such as Indonesia and the Philippines, and subsequently spread onto mainland Eurasia and North Africa. The earliest fossil finds of the species come from both Europe and Asia, and date back to the Early Pleistocene. By the late Villafranchian, S. scrofa largely displaced the related S. strozzii, a large, possibly swamp-adapted suid ancestral to the modern S. verrucosus throughout the Eurasian mainland, restricting it to insular Asia. Its closest wild relative is the bearded pig of Malacca and surrounding islands.

 

Domestication

With the exception of domestic pigs in Timor and Papua New Guinea (which appear to be of Sulawesi warty pig stock), the wild boar is the ancestor of most pig breeds. Archaeological evidence suggests that pigs were domesticated from wild boar as early as 13,000–12,700 BCE in the Near East in the Tigris Basin, being managed in the wild in a way similar to the way they are managed by some modern New Guineans. Remains of pigs have been dated to earlier than 11,400 BCE in Cyprus. Those animals must have been introduced from the mainland, which suggests domestication in the adjacent mainland by then. There was also a separate domestication in China, which took place about 8,000 years ago.

 

DNA evidence from sub-fossil remains of teeth and jawbones of Neolithic pigs shows that the first domestic pigs in Europe had been brought from the Near East. This stimulated the domestication of local European wild boars, resulting in a third domestication event with the Near Eastern genes dying out in European pig stock. Modern domesticated pigs have involved complex exchanges, with European domesticated lines being exported in turn to the ancient Near East. Historical records indicate that Asian pigs were introduced into Europe during the 18th and early 19th centuries. Domestic pigs tend to have much more developed hindquarters than their wild boar ancestors, to the point where 70% of their body weight is concentrated in the posterior, which is the opposite of wild boar, where most of the muscles are concentrated on the head and shoulders.

 

Synonymous species

The Heude's pig (Sus bucculentus), also known as the Indochinese warty pig or Vietnam warty pig, was an alleged pig species found in Laos and Vietnam. It was virtually unknown and was feared extinct, until the discovery of a skull from a recently killed individual in the Annamite Range, Laos, in 1995. Subsequent studies indicated that Sus bucculentus was not a valid taxon. As of 2022 the Mammal Diversity Database included it in Sus scrofa.

 

Description

The wild boar is a bulky, massively built suid with short and relatively thin legs. The trunk is short and robust, while the hindquarters are comparatively underdeveloped. The region behind the shoulder blades rises into a hump and the neck is short and thick to the point of being nearly immobile. The animal's head is very large, taking up to one-third of the body's entire length. The structure of the head is well suited for digging. The head acts as a plough, while the powerful neck muscles allow the animal to upturn considerable amounts of soil: it is capable of digging 8–10 cm (3.1–3.9 in) into frozen ground and can upturn rocks weighing 40–50 kg (88–110 lb). The eyes are small and deep-set and the ears long and broad. The species has well developed canine teeth, which protrude from the mouths of adult males. The medial hooves are larger and more elongated than the lateral ones and are capable of quick movements. The animal can run at a maximum speed of 40 km/h (25 mph) and jump at a height of 140–150 cm (55–59 in).

 

Sexual dimorphism is very pronounced in the species, with males being typically 5–10% larger and 20–30% heavier than females. Males also sport a mane running down the back, which is particularly apparent during autumn and winter. The canine teeth are also much more prominent in males and grow throughout life. The upper canines are relatively short and grow sideways early in life, though they gradually curve upwards. The lower canines are much sharper and longer, with the exposed parts measuring 10–12 cm (3.9–4.7 in) in length. In the breeding period, males develop a coating of subcutaneous tissue, which may be 2–3 cm (0.79–1.18 in) thick, extending from the shoulder blades to the rump, thus protecting vital organs during fights. Males sport a roughly egg-sized sack near the opening of the penis, which collects urine and emits a sharp odour. The function of this sack is not fully understood.

 

Adult size and weight is largely determined by environmental factors; boars living in arid areas with little productivity tend to attain smaller sizes than their counterparts inhabiting areas with abundant food and water. In most of Europe, males average 75–100 kg (165–220 lb) in weight, 75–80 cm (30–31 in) in shoulder height and 150 cm (59 in) in body length, whereas females average 60–80 kg (130–180 lb) in weight, 70 cm (28 in) in shoulder height and 140 cm (55 in) in body length. In Europe's Mediterranean regions, males may reach average weights as low as 50 kg (110 lb) and females 45 kg (99 lb), with shoulder heights of 63–65 cm (25–26 in). In the more productive areas of Eastern Europe, males average 110–130 kg (240–290 lb) in weight, 95 cm (37 in) in shoulder height and 160 cm (63 in) in body length, while females weigh 95 kg (209 lb), reach 85–90 cm (33–35 in) in shoulder height, and reach 145 cm (57 in) in body length. In Western and Central Europe, the largest males weigh 200 kg (440 lb) and females 120 kg (260 lb). In Northeastern Asia, large males can reach brown bear-like sizes, weighing 270 kg (600 lb) and measuring 110–118 cm (43–46 in) in shoulder height. Some adult males in Ussuriland and Manchuria have been recorded to weigh 300–350 kg (660–770 lb) and measure 125 cm (49 in) in shoulder height. Adults of this size are generally immune from wolf predation. Such giants are rare in modern times, due to past overhunting preventing animals from attaining their full growth.

 

The winter coat consists of long, coarse bristles underlaid with short brown downy fur. The length of these bristles varies along the body, with the shortest being around the face and limbs and the longest running along the back. These back bristles form the aforementioned mane prominent in males and stand erect when the animal is agitated. Colour is highly variable; specimens around Lake Balkhash are very lightly coloured, and can even be white, while some boars from Belarus and Ussuriland can be black. Some subspecies sport a light-coloured patch running backward from the corners of the mouth. Coat colour also varies with age, with piglets having light brown or rusty-brown fur with pale bands extending from the flanks and back.

 

The wild boar produces a number of different sounds which are divided into three categories:

 

Contact calls: Grunting noises which differ in intensity according to the situation. Adult males are usually silent, while females frequently grunt and piglets whine. When feeding, boars express their contentment through purring. Studies have shown that piglets imitate the sounds of their mother, thus different litters may have unique vocalisations.

Alarm calls: Warning cries emitted in response to threats. When frightened, boars make loud huffing ukh! ukh! sounds or emit screeches transcribed as gu-gu-gu.

Combat calls: High-pitched, piercing cries.

Its sense of smell is very well developed to the point that the animal is used for drug detection in Germany. Its hearing is also acute, though its eyesight is comparatively weak, lacking color vision and being unable to recognise a standing human 10–15 metres (33–49 ft) away.

 

Pigs are one of four known mammalian taxa which possess mutations in the nicotinic acetylcholine receptor that protect against snake venom. Mongooses, honey badgers, hedgehogs, and pigs all have modifications to the receptor pocket which prevents the snake venom α-neurotoxin from binding. These represent four separate, independent mutations.

 

Social behaviour and life cycle

Boars are typically social animals, living in female-dominated sounders consisting of barren sows and mothers with young led by an old matriarch. Male boars leave their sounder at the age of 8–15 months, while females either remain with their mothers or establish new territories nearby. Subadult males may live in loosely knit groups, while adult and elderly males tend to be solitary outside the breeding season.

 

The breeding period in most areas lasts from November to January, though most mating only lasts a month and a half. Prior to mating, the males develop their subcutaneous armour in preparation for confronting rivals. The testicles double in size and the glands secrete a foamy yellowish liquid. Once ready to reproduce, males travel long distances in search of a sounder of sows, eating little on the way. Once a sounder has been located, the male drives off all young animals and persistently chases the sows. At this point, the male fiercely fights potential rivals. A single male can mate with 5–10 sows. By the end of the rut, males are often badly mauled and have lost 20% of their body weight, with bite-induced injuries to the penis being common. The gestation period varies according to the age of the expecting mother. For first-time breeders, it lasts 114–130 days, while it lasts 133–140 days in older sows. Farrowing occurs between March and May, with litter sizes depending on the age and nutrition of the mother. The average litter consists of 4–6 piglets, with the maximum being 10–12. The piglets are whelped in a nest constructed from twigs, grasses and leaves. Should the mother die prematurely, the piglets are adopted by the other sows in the sounder.

 

Newborn piglets weigh around 600–1,000 grams, lacking underfur and bearing a single milk incisor and canine on each half of the jaw. There is intense competition between the piglets over the most milk-rich nipples, as the best-fed young grow faster and have stronger constitutions. The piglets do not leave the lair for their first week of life. Should the mother be absent, the piglets lie closely pressed to each other. By two weeks of age, the piglets begin accompanying their mother on her journeys. Should danger be detected, the piglets take cover or stand immobile, relying on their camouflage to keep them hidden. The neonatal coat fades after three months, with adult colouration being attained at eight months. Although the lactation period lasts 2.5–3.5 months, the piglets begin displaying adult feeding behaviours at the age of 2–3 weeks. The permanent dentition is fully formed by 1–2 years. With the exception of the canines in males, the teeth stop growing during the middle of the fourth year. The canines in old males continue to grow throughout their lives, curving strongly as they age. Sows attain sexual maturity at the age of one year, with males attaining it a year later. However, estrus usually first occurs after two years in sows, while males begin participating in the rut after 4–5 years, as they are not permitted to mate by the older males. The maximum lifespan in the wild is 10–14 years, though few specimens survive past 4–5 years. Boars in captivity have lived for 20 years.

 

Behaviour and ecology

The wild boar inhabits a diverse array of habitats from boreal taigas to deserts. In mountainous regions, it can even occupy alpine zones, occurring up to 1,900 m (6,200 ft) in the Carpathians, 2,600 m (8,500 ft) in the Caucasus and up to 3,600–4,000 m (11,800–13,100 ft) in the mountains in Central Asia and Kazakhstan. In order to survive in a given area, wild boars require a habitat fulfilling three conditions: heavily brushed areas providing shelter from predators, water for drinking and bathing purposes and an absence of regular snowfall.

 

The main habitats favored by boars in Europe are deciduous and mixed forests, with the most favorable areas consisting of forest composed of oak and beech enclosing marshes and meadows. In the Białowieża Forest, the animal's primary habitat consists of well-developed broad-leaved and mixed forests, along with marshy mixed forests, with coniferous forests and undergrowths being of secondary importance. Forests made up entirely of oak groves and beeches are used only during the fruit-bearing season. This is in contrast to the Caucasian and Transcaucasian mountain areas, where boars will occupy such fruit-bearing forests year-round. In the mountainous areas of the Russian Far East, the species inhabits nutpine groves, hilly mixed forests where Mongolian oak and Korean pine are present, swampy mixed taiga and coastal oak forests. In Transbaikalia, boars are restricted to river valleys with nut pine and shrubs. Boars are regularly encountered in pistachio groves in winter in some areas of Tajikistan and Turkmenistan, while in spring they migrate to open deserts; boar have also colonized deserts in several areas they have been introduced to.

 

On the islands of Komodo and Rinca, the boar mostly inhabits savanna or open monsoon forests, avoiding heavily forested areas unless pursued by humans. Wild boar are known to be competent swimmers, capable of covering long distances. In 2013, one boar was reported to have completed the 11-kilometre (7 mi) swim from France to Alderney in the Channel Islands. Due to concerns about disease, it was shot and incinerated.

 

Wild boar rest in shelters, which contain insulating material like spruce branches and dry hay. These resting places are occupied by whole families (though males lie separately) and are often located in the vicinity of streams, in swamp forests and in tall grass or shrub thickets. Boars never defecate in their shelters and will cover themselves with soil and pine needles when irritated by insects.

 

Diet

The wild boar is a highly versatile omnivore, whose diversity in choice of food is comparable to that of humans. Their foods can be divided into four categories:

 

Rhizomes, roots, tubers and bulbs, all of which are dug up throughout the year in the animal's whole range.

Nuts, berries and seeds, which are consumed when ripened and are dug up from the snow when necessary.

Leaves, bark, twigs and shoots, along with garbage.

Earthworms, insects, mollusks, fish, rodents, insectivores, bird eggs, lizards, snakes, frogs and carrion. Most of these prey items are taken in warm periods.

A 50 kg (110 lb) boar needs around 4,000–4,500 calories of food per day, though this required amount increases during winter and pregnancy, with the majority of its diet consisting of food items dug from the ground, like underground plant material and burrowing animals. Acorns and beechnuts are invariably its most important food items in temperate zones, as they are rich in the carbohydrates necessary for the buildup of fat reserves needed to survive lean periods. In Western Europe, underground plant material favoured by boars includes bracken, willow herb, bulbs, meadow herb roots and bulbs and the bulbs of cultivated crops. Such food is favoured in early spring and summer, but may also be eaten in autumn and winter during beechnut and acorn crop failures. Should regular wild foods become scarce, boars will eat tree bark and fungi, as well as visit cultivated potato and artichoke fields. Boar soil disturbance and foraging have been shown to facilitate invasive plants. Boars of the vittatus subspecies in Ujung Kulon National Park in Java differ from most other populations by their primarily frugivorous diet, which consists of 50 different fruit species, especially figs, thus making them important seed dispersers. The wild boar can consume numerous genera of poisonous plants without ill effect, including Aconitum, Anemone, Calla, Caltha, Ferula and Pteridium.

 

Boars may occasionally prey on small vertebrates like newborn deer fawns, leporids and galliform chicks. Boars inhabiting the Volga Delta and near some lakes and rivers of Kazakhstan have been recorded to feed extensively on fish like carp and Caspian roach. Boars in the former area will also feed on cormorant and heron chicks, bivalved molluscs, trapped muskrats and mice. There is at least one record of a boar killing and eating a bonnet macaque in southern India's Bandipur National Park, though this may have been a case of intraguild predation, brought on by interspecific competition for human handouts. There is also at least one recorded case of a group of wild boar attacking, killing, and eating an adult, healthy female axis deer (Axis axis) as a pack.

 

Predators

Piglets are vulnerable to attack from medium-sized felids like Eurasian lynx (Lynx lynx), jungle cats (Felis chaus), and snow leopards (Panthera uncia), as well as other carnivorans like brown bears (Ursus arctos) and yellow-throated martens (Martes flavigula).

 

The wolf (Canis lupus) is the main predator of wild boar throughout most of its range. A single wolf can kill around 50 to 80 boars of differing ages in one year. In Italy and Belarus' Belovezhskaya Pushcha National Park, boars are the wolf's primary prey, despite an abundance of alternative, less powerful ungulates. Wolves are particularly threatening during the winter, when deep snow impedes the boars' movements. In the Baltic regions, heavy snowfall can allow wolves to eliminate boars from an area almost completely. Wolves primarily target piglets and subadults and only rarely attack adult sows. Adult males are usually avoided entirely. Dholes (Cuon alpinus) may also prey on boars, to the point of keeping their numbers down in northwestern Bhutan, despite there being many more cattle in the area.

 

Leopards (Panthera pardus) are predators of wild boar in the Caucasus (particularly Transcaucasia), the Russian Far East, India, China and Iran. In most areas, boars constitute only a small part of the leopard's diet. However, in Iran's Sarigol National Park, boars are the second most frequently targeted prey species after mouflon (Ovis gmelini), though adult individuals are generally avoided, as they are above the leopard's preferred weight range of 10–40 kg (22–88 lb). This dependence on wild boar is largely due in part to the local leopard subspecies' large size.

 

Boars of all ages were once the primary prey of the tiger (Panthera tigris) in Transcaucasia, Kazakhstan, Middle Asia and the Far East up until the late 19th century. In modern times, tiger numbers are too low to have a limiting effect on boar populations. A single tiger can systematically destroy an entire sounder by preying on its members one by one, before moving on to another sounder. Tigers have been noted to chase boars for longer distances than with other prey. In two rare cases, boars were reported to gore a small tiger and a tigress to death in self-defense. A "large male tiger" died of wounds inflicted by an old wild boar it had killed in "a battle royal" between the two animals.

 

In the Amur region, wild boars are one of the two most important prey species for Siberian tigers, alongside the Manchurian wapiti (Cervus canadensis xanthopygus), with the two species collectively comprising roughly 80% of the felid's prey. In Sikhote Alin, a tiger can kill 30–34 boars a year. Studies of tigers in India indicate that boars are usually secondary in preference to various cervids and bovids, though when boars are targeted, healthy adults are caught more frequently than young and sick specimens.

 

On the islands of Komodo, Rinca and Flores, the boar's main predator is the Komodo dragon (Varanus komodoensis).

 

Distribution and habitat

Reconstructed range

The species originally occurred in North Africa and much of Eurasia; from the British Isles to Korea and the Sunda Islands. The northern limit of its range extended from southern Scandinavia to southern Siberia and Japan. Within this range, it was only absent in extremely dry deserts and alpine zones. It was once found in North Africa along the Nile valley up to Khartoum and north of the Sahara. The species occurs on a few Ionian and Aegean Islands, sometimes swimming between islands. The reconstructed northern boundary of the animal's Asian range ran from Lake Ladoga (at 60°N) through the area of Novgorod and Moscow into the southern Urals, where it reached 52°N. From there, the boundary passed Ishim and farther east the Irtysh at 56°N. In the eastern Baraba steppe (near Novosibirsk) the boundary turned steep south, encircled the Altai Mountains and went again eastward including the Tannu-Ola Mountains and Lake Baikal. From here, the boundary went slightly north of the Amur River eastward to its lower reaches at the Sea of Okhotsk. On Sakhalin, there are only fossil reports of wild boar. The southern boundaries in Europe and Asia were almost invariably identical to the seashores of these continents. It is absent in the dry regions of Mongolia from 44 to 46°N southward, in China westward of Sichuan and in India north of the Himalayas. It is absent in the higher elevations of the Pamir and the Tian Shan, though they do occur in the Tarim basin and on the lower slopes of the Tien Shan.

 

Present range

In recent centuries, the range of wild boar has changed dramatically, largely due to hunting by humans and more recently because of captive wild boar escaping into the wild. Prior to the 20th century, boar populations had declined in numerous areas, with British populations probably becoming extinct during the 13th century. In the warm period after the ice age, wild boar lived in the southern parts of Sweden and Norway and north of Lake Ladoga in Karelia. It was previously thought that the species did not live in Finland during prehistory because no prehistoric wild boar bones had been found within the borders of the country. It was not until 2013, when a wild boar bone was found in Askola, that the species was found to have lived in Finland more than 8,000 years ago. It is believed, however, that man prevented its establishment by hunting. In Denmark, the last boar was shot at the beginning of the 19th century, and by 1900 they were absent in Tunisia and Sudan and large areas of Germany, Austria and Italy. In Russia, they were extirpated in wide areas by the 1930s. The last boar in Egypt reportedly died on 20 December 1912 in the Giza Zoo, with wild populations having disappeared by 1894–1902. Prince Kamal el Dine Hussein attempted to repopulate Wadi El Natrun with boars of Hungarian stock, but they were quickly exterminated by poachers.

 

A revival of boar populations began in the middle of the 20th century. By 1950, wild boar had once again reached their original northern boundary in many parts of their Asiatic range. By 1960, they reached Leningrad and Moscow and by 1975, they were to be found in Archangelsk and Astrakhan. In the 1970s they again occurred in Denmark and Sweden, where captive animals escaped and now survive in the wild. In England, wild boar populations re-established themselves in the 1990s, after escaping from specialist farms that had imported European stock.

 

Status in Great Britain

By the 11th century, wild boars were apparently already becoming rare in Britain. A 1087 forestry law enacted by William the Conqueror punished through blinding the unlawful killing of a boar. Charles I attempted to reintroduce the species into the New Forest, but this population was exterminated in the 17th century during the English Civil War. Between their medieval extinction and the 1980s, when wild boar farming began, only a handful of captive wild boar, imported from the continent, were present in Britain. Occasional escapes of wild boar from wildlife parks have occurred as early as the 1970s, but since the early 1990s significant populations have re-established themselves after escapes from farms, the number of which has increased as the demand for meat from the species has grown. A 1998 MAFF (now DEFRA) study on wild boar living wild in Britain confirmed the presence of two populations of wild boar living in Britain; one in Kent/East Sussex and another in Dorset.

 

Another DEFRA report, in February 2008, confirmed the existence of these two sites as 'established breeding areas' and identified a third in Gloucestershire/Herefordshire; in the Forest of Dean/Ross on Wye area. A 'new breeding population' was also identified in Devon. There is another significant population in Dumfries and Galloway. Populations estimates were as follows:

 

The largest population, in Kent/East Sussex, was then estimated at 200 animals in the core distribution area.

The smallest, in west Dorset, was estimated to be fewer than 50 animals.

Since winter 2005–2006 significant escapes/releases have also resulted in animals colonizing areas around the fringes of Dartmoor, in Devon. These are considered as an additional single 'new breeding population' and currently estimated to be up to 100 animals.

Population estimates for the Forest of Dean are disputed as, at the time that the DEFRA population estimate was 100, a photo of a boar sounder in the forest near Staunton with over 33 animals visible was published and at about the same time over 30 boar were seen in a field near the original escape location of Weston under Penyard many kilometres or miles away. In early 2010 the Forestry Commission embarked on a cull, with the aim of reducing the boar population from an estimated 150 animals to 100. By August it was stated that efforts were being made to reduce the population from 200 to 90, but that only 25 had been killed. The failure to meet cull targets was confirmed in February 2011.

 

Wild boars have crossed the River Wye into Monmouthshire, Wales. Iolo Williams, the BBC Wales wildlife expert, attempted to film Welsh boar in late 2012. Many other sightings, across the UK, have also been reported. The effects of wild boar on the U.K.'s woodlands were discussed with Ralph Harmer of the Forestry Commission on the BBC Radio's Farming Today radio programme in 2011. The programme prompted activist writer George Monbiot to propose a thorough population study, followed by the introduction of permit-controlled culling.

 

In Scotland wild boar can be killed legally without a license and are culled by land managers as wild populations appear occasionally.

 

Introduction to North America

Wild boars are an invasive species in the Americas, having been introduced by European explorers and settlers in the 16th century to serve as a source of food. Wild boars now cause problems including out-competing native species for food, destroying the nests of ground-nesting species, killing fawns and young domestic livestock, destroying agricultural crops, eating tree seeds and seedlings, destroying native vegetation and wetlands through wallowing, damaging water quality, coming into violent conflict with humans and pets and carrying pig and human diseases including brucellosis, trichinosis and pseudorabies. In some jurisdictions, it is illegal to import, breed, release, possess, sell, distribute, trade, transport, hunt, or trap Eurasian boars. Hunting and trapping is done systematically, to increase the chance of eradication and to remove the incentive to illegally release boars, which have mostly been spread deliberately by sport hunters.

 

History

While domestic pigs, both captive and feral (popularly termed "razorbacks"), have been in North America since the earliest days of European colonization, pure wild boars were not introduced into the New World until the 19th century. The suids were released into the wild by wealthy landowners as big game animals. The initial introductions took place in fenced enclosures, though several escapes occurred, with the escapees sometimes intermixing with already established feral pig populations.

 

The first of these introductions occurred in New Hampshire in 1890. Thirteen wild boars from Germany were purchased by Austin Corbin from Carl Hagenbeck and released into a 9,500-hectare (23,000-acre) game preserve in Sullivan County. Several of these boars escaped, though they were quickly hunted down by locals. Two further introductions were made from the original stocking, with several escapes taking place due to breaches in the game preserve's fencing. These escapees have ranged widely, with some specimens having been observed crossing into Vermont.

 

In 1902, 15–20 wild boar from Germany were released into a 3,200-hectare (7,900-acre) estate in Hamilton County, New York. Several specimens escaped six years later, dispersing into the William C. Whitney Wilderness Area, with their descendants surviving for at least 20 years.

 

The most extensive boar introduction in the US took place in western North Carolina in 1912, when 13 boars of undetermined European origin were released into two fenced enclosures in a game preserve in Hooper Bald, Graham County. Most of the specimens remained in the preserve for the next decade, until a large-scale hunt caused the remaining animals to break through their confines and escape. Some of the boars migrated to Tennessee, where they intermixed with both free-ranging and feral pigs in the area. In 1924, a dozen Hooper Bald wild pigs were shipped to California and released in a property between Carmel Valley and the Los Padres National Forest. These hybrid boar were later used as breeding stock on various private and public lands throughout the state, as well as in other states like Florida, Georgia, South Carolina, West Virginia and Mississippi.

 

Several wild boars from Leon Springs and the San Antonio, Saint Louis and San Diego Zoos were released in the Powder Horn Ranch in Calhoun County, Texas, in 1939. These specimens escaped and established themselves in surrounding ranchlands and coastal areas, with some crossing the Espiritu Santo Bay and colonizing Matagorda Island. Descendants of the Powder Horn Ranch boars were later released onto San José Island and the coast of Chalmette, Louisiana.

 

Wild boar of unknown origin were stocked in a ranch in the Edwards Plateau in the 1940s, only to escape during a storm and hybridize with local feral pig populations, later spreading into neighboring counties.

 

Starting in the mid-1980s, several boars purchased from the San Diego Zoo and Tierpark Berlin were released into the United States. A decade later, more specimens from farms in Canada and Białowieża Forest were let loose. In recent years, wild pig populations have been reported in 44 states within the US, most of which are likely wild boar–feral hog hybrids. Pure wild boar populations may still be present, but are extremely localized.

 

Introduction and lack of control in South America

In South America, the European boar is believed to have been introduced for the first time in Argentina and Uruguay around the 20th century for breeding purposes. In Brazil, the creation of wild boar and hybrids started on a large scale in the mid-1990s. With the invasion of wild boar that crossed the border and entered Rio Grande do Sul around 1989, and the escape and intentional release by several Brazilian breeders in the late 1990s – in response to a IBAMA decision against the import and breeding of wild boar in 1998 – numerous feral species formed a growing population, which progressively advances in Brazilian territory. The species has no natural predators in Brazil, as it is an exotic species, in addition to breeding with the domestic pig, generating the so-called "javaporco" (neologism created to define this hybrid), factors that contribute to the exaggerated increase in the population. With its population in continuous and uncontrolled growth, without predators, the wild boar causes environmental damage, contributing to the aggradation of river and stream springs, attacking native species feeding on eggs and puppies, causing damage to fauna, flora and to agriculture and livestock, since it also attacks farm animals and can carry various diseases, including zoonosis.

 

Pest control in Brazil

As a form of control for the wild boar population (which is considered a pest and harmful species), hunting and killing are allowed for Collectors, Shooters and Hunters (CACs) duly registered by the environmental control agency, IBAMA, which, on the other hand, seeks to encourage the preservation of similar species of native peccaries, such as the "queixada" and the "caititu".

 

Effect on other habitats

Wild boars negatively impact other habitats through the destruction of the environment, or homes of wildlife. When wild boars invade new areas, they adapt to the new area by trampling and rooting, as well as displacing many saplings/nutrients. This causes a decrease in growing of many plants and trees. Water is also affected negatively by wild boars. When wild boars are active in streams, or small pools of water, it causes increased turbidity (excessive silt and particle suspension). In some cases, the fecal coliform concentration increases to dangerous levels because of wild boars. Aquatic wildlife is affected, more prominently fish, and amphibians. Wild boars have caused a great decrease in over 300 animal or plant species, 250 being endangered or threatened.

 

The boars cause many habitats to become less diverse because of their feeding behaviors and predation. Wild boars will dig up eggs of species and eat them, as well as killing other wildlife for food. When these boars compete with other species for resources, they usually come out successful. A study published in the Journal of Experimental Marine Biology and Ecology was conducted on the results of Feral Swine control. Only two years after the control started, the amount of turtle nests jumped from 57 to 143, and the turtle nest predation percent dropped from 74 to 15. They kill and eat deers, lizards, birds, snakes, and more. These boars are called "opportunist omnivores", which means they eat almost anything. This means they can survive almost anywhere. A big surplus of food and the ability to adapt to any new place causes lots of breeding. All of these factors make it difficult to get rid of wild boars. Wild boars also tend to carry diseases and numerous pathogens. This also adds to the decrease in diversity among species.

 

Diseases and parasites

Wild boars are known to host at least 20 different parasitic worm species, with maximum infections occurring in summer. Young animals are vulnerable to helminths like Metastrongylus, which are consumed by boars through earthworms and cause death by parasitising the lungs. Wild boar also carry parasites known to infect humans, including Gastrodiscoides, Trichinella spiralis, Taenia solium, Balantidium coli and Toxoplasma gondii. Wild boar in southern regions are frequently infested with ticks (Dermacentor, Rhipicephalus, and Hyalomma) and hog lice. The species also suffers from blood-sucking flies, which it escapes by bathing frequently or hiding in dense shrubs.

 

Swine plague spreads very quickly in wild boar, with epizootics being recorded in Germany, Poland, Hungary, Belarus, the Caucasus, the Far East, Kazakhstan and other regions. Foot-and-mouth disease can also take on epidemic proportions in boar populations. The species occasionally, but rarely contracts Pasteurellosis, hemorrhagic sepsis, tularemia, and anthrax. Wild boar may on occasion contract swine erysipelas through rodents or hog lice and ticks.

 

Relationships with humans

The wild boar features prominently in the cultures of Indo-European people, many of which saw the animal as embodying warrior virtues. Cultures throughout Europe and Asia Minor saw the killing of a boar as proof of one's valor and strength. Neolithic hunter gatherers depicted reliefs of ferocious wild boars on their temple pillars at Göbekli Tepe some 11,600 years ago. Virtually all heroes in Greek mythology fight or kill a boar at one point. The demigod Herakles' third labour involves the capture of the Erymanthian Boar, Theseus slays the wild sow Phaea, and a disguised Odysseus is recognised by his handmaiden Eurycleia by the scars inflicted on him by a boar during a hunt in his youth. To the mythical Hyperboreans, the boar represented spiritual authority. Several Greek myths use the boar as a symbol of darkness, death and winter. One example is the story of the youthful Adonis, who is killed by a boar and is permitted by Zeus to depart from Hades only during the spring and summer period. This theme also occurs in Irish and Egyptian mythology, where the animal is explicitly linked to the month of October, therefore autumn. This association likely arose from aspects of the boar's actual nature. Its dark colour was linked to the night, while its solitary habits, proclivity to consume crops and nocturnal nature were associated with evil. The foundation myth of Ephesus has the city being built over the site where Prince Androklos of Athens killed a boar Boars were frequently depicted on Greek funerary monuments alongside lions, representing gallant losers who have finally met their match, as opposed to victorious hunters as lions are. The theme of the doomed, yet valorous boar warrior also occurred in Hittite culture, where it was traditional to sacrifice a boar alongside a dog and a prisoner of war after a military defeat

 

The boar as a warrior also appears in Germanic cultures, with its image having been frequently engraved on shields and swords. They also feature on Germanic boar helmets, such as the Benty Grange helmet, where it was believed to offer protection to the wearer and has been theorised to have been used in spiritual transformations into swine, similar to berserkers. The boar features heavily in religious practice in Germanic paganism where it is closely associated with Freyr and has also been suggested to have been a totemic animal to the Swedes, especially to the Yngling royal dynasty who claimed descent from the god.

 

According to Tacitus, the Baltic Aesti featured boars on their helmets and may have also worn boar masks. The boar and pig were held in particularly high esteem by the Celts, who considered them to be their most important sacred animal. Some Celtic deities linked to boars include Moccus and Veteris. It has been suggested that some early myths surrounding the Welsh hero Culhwch involved the character being the son of a boar god. Nevertheless, the importance of the boar as a culinary item among Celtic tribes may have been exaggerated in popular culture by the Asterix series, as wild boar bones are rare among Celtic archaeological sites and the few that do occur show no signs of butchery, having probably been used in sacrificial rituals.

 

The boar also appears in Vedic mythology and Hindu mythology. A story present in the Brahmanas has the god Indra slaying an avaricious boar, who has stolen the treasure of the asuras, then giving its carcass to the god Vishnu, who offered it as a sacrifice to the gods. In the story's retelling in the Charaka Samhita, the boar is described as a form of Prajapati and is credited with having raised the Earth from the primeval waters. In the Ramayana and the Puranas, the same boar is portrayed as Varaha, an avatar of Vishnu.

 

In Japanese culture, the boar is widely seen as a fearsome and reckless animal, to the point that several words and expressions in Japanese referring to recklessness include references to boars. The boar is the last animal of the Oriental zodiac, with people born during the year of the Pig being said to embody the boar-like traits of determination and impetuosity. Among Japanese hunters, the boar's courage and defiance is a source of admiration and it is not uncommon for hunters and mountain people to name their sons after the animal inoshishi (猪). Boars are also seen as symbols of fertility and prosperity; in some regions, it is thought that boars are drawn to fields owned by families including pregnant women, and hunters with pregnant wives are thought to have greater chances of success when boar hunting. The animal's link to prosperity was illustrated by its inclusion on the ¥10 note during the Meiji period and it was once believed that a man could become wealthy by keeping a clump of boar hair in his wallet.

 

In the folklore of the Mongol Altai Uriankhai tribe, the wild boar was associated with the watery underworld, as it was thought that the spirits of the dead entered the animal's head, to be ultimately transported to the water. Prior to the conversion to Islam, the Kyrgyz people believed that they were descended from boars and thus did not eat pork. In Buryat mythology, the forefathers of the Buryats descended from heaven and were nourished by a boar. In China, the boar is the emblem of the Miao people.

 

The boar (sanglier) is frequently displayed in English, Scottish and Welsh heraldry. As with the lion, the boar is often shown as armed and langued. As with the bear, Scottish and Welsh heraldry displays the boar's head with the neck cropped, unlike the English version, which retains the neck. The white boar served as the badge of King Richard III of England, who distributed it among his northern retainers during his tenure as Duke of Gloucester.

 

As a game animal and food source

Humans have been hunting boar for millennia, the earliest artistic depictions of such activities dating back to the Upper Paleolithic. The animal was seen as a source of food among the Ancient Greeks, as well as a sporting challenge and source of epic narratives. The Romans inherited this tradition, with one of its first practitioners being Scipio Aemilianus. Boar hunting became particularly popular among the young nobility during the 3rd century BC as preparation for manhood and battle. A typical Roman boar hunting tactic involved surrounding a given area with large nets, then flushing the boar with dogs and immobilizing it with smaller nets. The animal would then be dispatched with a venabulum, a short spear with a crossguard at the base of the blade. More than their Greek predecessors, the Romans extensively took inspiration from boar hunting in their art and sculpture. With the ascension of Constantine the Great, boar hunting took on Christian allegorical themes, with the animal being portrayed as a "black beast" analogous to the dragon of Saint George.

 

Boar hunting continued after the fall of the Western Roman Empire, though the Germanic tribes considered the red deer to be a more noble and worthy quarry. The post-Roman nobility hunted boar as their predecessors did, but primarily as training for battle rather than sport. It was not uncommon for medieval hunters to deliberately hunt boars during the breeding season when the animals were more aggressive. During the Renaissance, when deforestation and the introduction of firearms reduced boar numbers, boar hunting became the sole prerogative of the nobility, one of many charges brought up against the rich during the German Peasants' War and the French Revolution.

 

During the mid-20th century, 7,000–8,000 boars were caught in the Caucasus, 6,000–7,000 in Kazakhstan and about 5,000 in Central Asia during the Soviet period, primarily through the use of dogs and beats. In Nepal, farmers and poachers eliminate boars by baiting balls of wheat flour containing explosives with kerosene oil, with the animals' chewing motions triggering the devices.

 

Wild boar can thrive in captivity, though piglets grow slowly and poorly without their mothers. Products derived from wild boar include meat, hide and bristles. Apicius devotes a whole chapter to the cooking of boar meat, providing 10 recipes involving roasting, boiling and what sauces to use. The Romans usually served boar meat with garum. Boar's head was the centrepiece of most medieval Christmas celebrations among the nobility. Although growing in popularity as a captive-bred source of food, the wild boar takes longer to mature than most domestic pigs and it is usually smaller and produces less meat. Nevertheless, wild boar meat is leaner and healthier than pork, being of higher nutritional value and having a much higher concentration of essential amino acids. Most meat-dressing organizations agree that a boar carcass should yield 50 kg (110 lb) of meat on average. Large specimens can yield 15–20 kg (33–44 lb) of fat, with some giants yielding 30 kg (66 lb) or more. A boar hide can measure 3 m2 (4,700 sq in) and can yield 350–1,000 grams (12–35 oz) of bristle and 400 grams (14 oz) of underwool.

 

Boars can be damaging to agriculture in situations where their natural habitat is sparse. Populations living on the outskirts of towns or farms can dig up potatoes and damage melons, watermelons and maize. However, they generally only encroach upon farms when natural food is scarce. In the Belovezh forest for example, 34–47% of the local boar population will enter fields in years of moderate availability of natural foods. While the role of boars in damaging crops is often exaggerated, cases are known of boar depredations causing famines, as was the case in Hachinohe, Japan in 1749, where 3,000 people died of what became known as the "wild boar famine". Still, within Japanese culture, the boar's status as vermin is expressed through its title as "king of pests" and the popular saying (addressed to young men in rural areas) "When you get married, choose a place with no wild boar."

 

In Central Europe, farmers typically repel boars through distraction or fright, while in Kazakhstan it is usual to employ guard dogs in plantations. However, research shows that when compared with other mitigation tactics, hunting is the only strategy to significantly reduce crop damage by boars. Although large boar populations can play an important role in limiting forest growth, they are also useful in keeping pest populations such as June bugs under control. The growth of urban areas and the corresponding decline in natural boar habitats has led to some sounders entering human habitations in search of food. As in natural conditions, sounders in peri-urban areas are matriarchal, though males tend to be much less represented and adults of both sexes can be up to 35% heavier than their forest-dwelling counterparts. As of 2010, at least 44 cities in 15 countries have experienced problems of some kind relating to the presence of habituated wild boar.

 

A 2023 study found that allowing wild pigs to forage on edible garbage in large regional landfills results in those animals getting physically large/heavier, having larger litters of piglets, and causing more wild pig-vehicle collisions in the vicinity of the landfill. The effects of letting these pigs scavenge in these landfills can present unique challenges to population management, control, public safety, and disease transmission. Wild pigs foraging on edible food waste in landfills has also been identified as a vector that facilitates the spread of African swine fever virus.

 

Attacks on humans

Actual attacks on humans are rare, but can be serious, resulting in penetrating injuries to the lower part of the body. They generally occur during the boars' rutting season from November to January, in agricultural areas bordering forests or on paths leading through forests. The animal typically attacks by charging and pointing its tusks towards the intended victim, with most injuries occurring on the thigh region. Once the initial attack is over, the boar steps back, takes position and attacks again if the victim is still moving, only ending once the victim is completely incapacitated.

 

Boar attacks on humans have been documented throughout history. The Romans and Ancient Greeks wrote of these attacks (Odysseus was wounded by a boar and Adonis was killed by one). A 2012 study compiling recorded attacks from 1825 to 2012 found accounts of 665 human victims of both wild boars and feral pigs, with the majority (19%) of attacks in the animal's native range occurring in India. Most of the attacks occurred in rural areas during the winter months in non-hunting contexts and were committed by solitary males.

 

Management

Managing wild boar is a pressing task in both native and invasive contexts as they can be disrupting to other systems when not addressed. Wild boar find their success through adaptation of daily patterns to circumvent threats. They avoid human contact through nocturnal lifestyles, despite the fact that they are not evolutionarily predisposed, and alter their diets substantially based on what is available. These "adaptive generalists", can survive in a variety of landscapes, making the prediction of their movement patterns and any potential close contact areas crucial to limiting damage. All of these qualities make them equally difficult to manage or limit.

 

Within Central Europe, the native habitat of the wild boar, there has been a push to re-evaluate interactions between wild boar and humans, with the priority of fostering positive engagement. Negative media and public perception of wild boar as "crop raiders" have made those living alongside them less willing to accept the economic damages of their behaviors, as wild boar are seen as pests. This media tone impacts management policy, with every 10 negative articles increasing wild boar policy activity by 6.7%. Contrary to this portrayal, wild boar, when managed well within their natural environments, can be a crucial part of forest ecosystems.

 

Defining the limits of proper management is difficult, but the exclusion of wild boar from rare environments is generally agreed upon, as when not properly managed, they can damage agricultural ventures and harm vulnerable plant life. These damages are estimated at $800 million yearly in environmental and financial costs for the United States alone. The breadth of this damage is due to prior inattention and lack of management tactics for extended lengths of time. Managing wild boar is a complex task, as it involves coordinating a combination of crop harvest techniques, fencing, toxic bait, corrals, and hunting. The most common tactic employed by private land owners in the United States is recreational hunting, however, this is generally not as effective on its own. Management strategies are most successful when they take into account reproduction, dispersion, and the differences between ideal resources for males and females.

 

According to a study, wild boars are causing soil disturbance that, among other problems, globally results in annual carbon dioxide emissions equivalent to that of ~1.1 million passenger vehicles (4.9 Mt, 0.01% of all GHG emissions as of 2022), implying that as of 2021 hunted boar meat – unlike other meat products – has beneficial effects on the environment even though the effect would diminish if boars are introduced for meat production and consistently retaining small populations of boars may be preferable.

Porcupines are amongst the largest of the rodents weighing between 24 to 40 lb. (11 to 18 kg) and measuring from nose to tail between 31 to 39 in. (78 to 100 cm). As with all members of this family their incisor teeth must be in regular use to keep them in trim and prevent them from over growing.

The most distinctive feature of this mammal is the converted body hair, most of which is seen as a protective covering of sharp ended spines. These may be raised or lowered at will, both for body protection and as a means of communication. An angry or disturbed porcupine will raise it's spines and even rattle them as a means of warning to a would be aggressor. Predators of the Indian crested porcupine include large cats, caracals, wolves, striped hyenas, Asian wild dogs, saltwater crocodiles and humans.

Indian crested porcupines are found throughout southwest and central Asia. Due to their flexible environmental tolerances, Indian crested porcupines occupy a broad range of habitats. They prefer rocky hillsides, but are also common in tropical and temperate shrublands, grasslands, forests, plantations, and gardens. Their range seems to be limited by seasonal densities of forage and the availability of suitable substrates for digging burrows. They do not occur above latitudes where minimum night duration is less than 7 hours, presumably because of the amount of foraging time required to find food. They consume a variety of natural and agricultural plant material, including roots, bulbs, fruits, grains, drupe and tubers, along with insects and small vertebrates.

The Indian crested porcupine's conservation status is LC (least concern).

Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.

 

The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.

 

The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.

 

Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.

 

There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.

 

Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.

 

Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.

 

Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.

 

Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.

 

Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.

 

All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.

 

Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.

 

After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.

 

Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.

 

Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).

 

Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.

 

Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.

 

Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.

 

Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).

 

Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.

 

So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).

 

Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.

 

The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.

 

Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.

 

In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.

 

Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.

 

Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.

 

Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.

 

The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.

 

The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.

 

The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.

 

The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.

 

The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.

 

Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.

 

Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.

 

Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.

 

The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.

 

The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.

 

Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.

 

Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.

 

Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.

 

The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.

 

Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.

 

Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.

 

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.

 

The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.

 

The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.

 

The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.

 

The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).

 

The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.

 

Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.

 

There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.

 

Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.

 

Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.

 

As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.

 

The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).

 

The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.

 

Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.

 

Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.

 

Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.

 

Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.

 

A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.

 

An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.

  

Commentary.

 

Amazing Suilven changes in form

as we circumnavigate it.

From the west, a sugar-loaf dome, near vertical.

From others, a giant elephant.

West peak, its rump.

Central col, a dip in its backbone.

Easterly peak, a sharper point to the top of its skull.

From yet others it appears like an incisor tooth,

thrusting up from an undulating, rocky base

of “Knock and Lochan” or small hill and lake.

The mountains of Sutherland don’t reach 1,000 metres.

But because of their stark, isolated rise,

they seem double their actual height.

They arrest one’s attention.

They demand focus.

They bemuse, by constantly changing form, shape and character,

and none more so, than the captivating,

iconic, monolith known as Suilven!

 

Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.

 

The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.

 

The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.

 

Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.

 

There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.

 

Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.

 

Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.

 

Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.

 

Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.

 

Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.

 

All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.

 

Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.

 

After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.

 

Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.

 

Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).

 

Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.

 

Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.

 

Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.

 

Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).

 

Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.

 

So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).

 

Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.

 

The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.

 

Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.

 

In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.

 

Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.

 

Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.

 

Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.

 

The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.

 

The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.

 

The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.

 

The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.

 

The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.

 

Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.

 

Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.

 

Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.

 

The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.

 

The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.

 

Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.

 

Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.

 

Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.

 

The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.

 

Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.

 

Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.

 

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.

 

The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.

 

The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.

 

The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.

 

The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).

 

The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.

 

Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.

 

There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.

 

Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.

 

Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.

 

As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.

 

The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).

 

The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.

 

Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.

 

Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.

 

Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.

 

Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.

 

A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.

 

An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.

  

Mursi woman without her giant lip plate, a sign of beauty in Mursi tribe, like in Surma one. When they are ready to marry, they start to make a hole in the lip with a wood stick.

It will be kept for one night , and is removed to put a bigger one. This is very painful at this time... Few months after, the lip plate has its full size, and the girl is seen as beautiful by the men.

The lip plate made of wood or terracotta, and they have to remove the lower incisors to let some space for the disc. it's amazing to see them speak without any trouble, put it and remove it as a classic jewel.

Sometimes the lip is broken by the pressure of the lip plate. This is a very big problem for the girl cos men will consider her as ugly, she won't be able to marry anyone in the tribe apart the old men or the sick people...

On this picture, a Mursi, the most agressive tribe i met.

Agressive in the way that when you come to see them (after hours of 4x4 on a very bad track), they only think about the money they can get from you! The craziest thing is that they ask for a fee to park the car (20 euros!) at the entrance of the village!!

They tend to use more and more things to decorate themselves and attract photographers!

You may have seen or read books about this area by great photographers those last years, and many of the people inside are just "disguised"...

But at the end, those tribes really live like in the primitives times, whitout anything around apart their cattle, and still fighting with other tribes to catch cows and women...

This is a daily reality in this area of the world!

7 000 tourists visit the mursis every year. It makes an average of 20 by day in a very big area, so it's very few.But as 70% are from Spain and pay a low fee to the tour operator, some tribes start to settle close to "hotels" or campings to get money from the photographers.

I had the chance to go in Omo valley with a guide who avoid those touristic spots.

The women are shaved, like the men, cos they hate hairiness!

 

© Eric Lafforgue

www.ericlafforgue.com

Saguis no terreno da Imprensa Nacional, em Brasília-DF, Brasil.

 

Um sagui[1][2] (do tupi sauín), soim ou mico são as designações comuns dadas a várias espécies de pequenos macacos pertencentes à família Callitrichidae. A palavra sagui tem origem no tupi e sua pronúncia é feita observando-se o som da vogal "u".

Estes primatas são representados por várias espécies em território brasileiro. Todos os quais possuem o dedo polegar da mão muito curto e não oponível, as unhas em forma de garras, e dentes molares de fórmula 2/2. São espécies de pequeno porte e de cauda longa.

São os menores símios do mundo, estão dispersos por toda a América do Sul e vivem geralmente em bandos que se hospedam em árvores, como os esquilos. Travessos e ágeis, movem-se em saltos bruscos, emitindo guinchos e assobios que são ouvidos de longe.

  

Sagui-de-tufos-brancos

Espécies

 

Família Callitrichidae

Callithrix jacchus - Sagui-de-tufos-brancos

Callithrix penicillata - Sagui-de-tufos-pretos

Callithrix kuhlii - Sagui-de-wied

Callithrix geoffroyi - Sagui-de-cara-branca

Callithrix flaviceps - Sagui-da-serra

Callithrix aurita - Sagui-da-serra-escuro

Callithrix argentata - Sagui-branco

Callithrix nigriceps - Sagui-de-cabeça-preta

Callithrix humeralifera - Sagui-de-santarém

Saguinus fuscicollis - Sagui-de-cara-suja

Saguinus imperator - Sagui-imperador

Saguinus labiatus - Sagui-de-bigode

Saguinus mystax - Sagui-de-boca-branca

Saguinus oedipus - Sagui-de-cabeça-branca

Saguinus bicolor - Sagui-de-coleira

Família Callimiconidae

Callimico goeldi - Sagui-goeldi

Referências

 

↑ michaelis.uol.com.br/moderno/portugues/index.php?lingua=p...

↑ Desde 1 de janeiro de 2009, em virtude da vigência do Acordo Ortográfico de 1990, a palavra não é mais grafada com trema (sagüi).

  

O sagüi (português brasileiro) ou sagui (português europeu) (AO 1990: sagui), soim, mico, marmoset (em inglês) ou tamarim (em inglês) são as designações comuns dadas a várias espécies de pequenos macacos pertencentes à família Callitrichidae.

Estes primatas são representados por várias espécies em território brasileiro. Todos os quais possuem o dedo polegar da mão muito curto e não oponível, as unhas em forma de garras, e dentes molares de fórmula 2/2. São espécies de pequeno porte e de cauda longa.

São os menores símios do mundo, estão dispersos por toda a América do Sul e vivem geralmente em bandos que se hospedam, como os esquilos em árvores. Travessos e ágeis, movem-se a saltos bruscos, emitindo guinchos e assobios que são ouvidos de longe.

 

Following, a text, in english, from Wikipedia the free encyclopédia:

 

Black-tufted marmoset at "Imprensa Nacional" (National Press)

The black-tufted marmoset (Callithrix penicillata), also known as Mico-estrela in Portuguese, is a species of New World monkey that lives primarily in the Neo-tropical gallery forests of the Brazilian Central Plateau. It ranges from Bahia to Paraná,[3] and as far inland as Goiás, between 14 and 25 degrees south of the equator. This marmoset typically resides in rainforests, living an arboreal life high in the trees, but below the canopy. They are only rarely spotted near the ground.

Physical description:

The black-tufted marmoset is characterized by black tufts of hair around their ears. It typically has some sparse white hairs on its face. It usually has a brown or black head and its limbs and upper body are gray, as well as its abdomen, while its rump and underside are usually black. Its tail is ringed with black and white and is not prehensile, but is used for balance. It does not have an opposable thumb and its nails tend to have a claw-like appearance. The black-tufted marmoset reaches a size of 19 to 22 cm and weighs up to 350 g.

Behavior:

Diurnal and arboreal, the black-tufted marmoset has a lifestyle very similar to other marmosets. It typically lives in family groups of 2 to 14. The groups usually consist of a reproductive couple and their offspring. Twins are very common among this species and the males, as well as juvenile offspring, often assist the female in the raising of the young.

Though the black-tufted marmoset lives in small family groups, it is believed that they share their food source, sap trees, with other marmoset groups. Scent marking does occur within these groups, but it is believed that the marking is to deter other species rather than other black-tufted marmoset groups, because other groups typically ignore these markings. They also appear to be migratory, often moving in relation to the wet or dry seasons, however, the extent of their migration is unknown.

Though communication between black-tufted marmosets has not been studied thoroughly, it is believed that it communicates through vocalizations. It has known predator-specific cries and appears to vocalize frequently outside of predator cries.

Food and predation:

The Black-tufted Marmoset diet consists primarily of tree sap which it gets by nibbling the bark with its long lower incisors. In periods of drought, it will also include fruit and insects in its diet. In periods of serious drought it has also been known to eat small arthropods, molluscs, bird eggs, baby birds and small vertebrates.

Large birds of prey are the greatest threat to the black-tufted marmoset, however, snakes and wild cats also pose a danger to them. Predator-specific vocalizations and visual scanning are its only anti-predation techniques.

Reproduction:

The black-tufted marmoset is monogamous and lives in family groups. It reproduces twice a year, producing 1 to 4 offspring, though most often just twins. Its gestation period is 150 days and offspring are weaned after 8 weeks. There is considerable parental investment by this species, with both parents, as well as older juveniles, helping to raise the young. The offspring are extremely dependent on their parents and though they are sexually mature at 18 months, they typically do not mate until much later, staying with their family group until they do.

Ecosystem roles and conservation status:

The black-tufted marmoset is a mutualist with many species of fruit trees because it distributes the seeds from the fruit it consumes throughout the forests. However, it is a parasite on other species of trees because it creates sores in trees in order to extract sap, while offering no apparent benefit to the trees. Though this marmoset is not a main food source to any specific species, it is a food source to a number of different species, specifically large birds of prey, wild cats, and snakes.

While there are no known negative effects of marmosets towards humans, it carries specific positive effects by being a highly valuable exotic pet. It is also used in zoo exhibits and scientific research.

The black-tufted marmoset is listed as having no special status on the IUCN Red List or the United States Endangered Species Act List. It is listed in Appendix II of CITES and is not currently considered an endangered or threatened species.

The ferret (Mustela furo) is a small, domesticated species belonging to the family Mustelidae. The ferret is most likely a domesticated form of the wild European polecat (Mustela putorius), evidenced by their interfertility. Physically, ferrets resemble other mustelids because of their long, slender bodies. Including their tail, the average length of a ferret is about 50 cm (20 in); they weigh between 0.7 and 2.0 kg (1.5 and 4.4 lb); and their fur can be black, brown, white, or a mixture of those colours. The species is sexually dimorphic, with males being considerably larger than females.

 

Ferrets may have been domesticated since ancient times, but there is widespread disagreement because of the sparseness of written accounts and the inconsistency of those which survive. Contemporary scholarship agrees that ferrets were bred for sport, hunting rabbits in a practice known as rabbiting. In North America, the ferret has become an increasingly prominent choice of household pet, with over five million in the United States alone. The legality of ferret ownership varies by location. In New Zealand and some other countries, restrictions apply due to the damage done to native fauna by feral colonies of polecat–ferret hybrids. The ferret has also served as a fruitful research animal, contributing to research in neuroscience and infectious disease, especially influenza.

 

The domestic ferret is often confused with the black-footed ferret (Mustela nigripes), a species native to North America.[1]

 

Etymology

The name "ferret" is derived from the Latin furittus, meaning "little thief", a likely reference to the common ferret penchant for secreting away small items.[2] In Old English (Anglo-Saxon), the animal was called mearþ. The word fyret seems to appear in Middle English in the 14th century from the Latin, with the modern spelling of "ferret" by the 16th century.[3]

 

The Greek word ἴκτις íktis, Latinized as ictis occurs in a play written by Aristophanes, The Acharnians, in 425 BC. Whether this was a reference to ferrets, polecats, or the similar Egyptian mongoose is uncertain.[3]

 

A male ferret is called a hob; a female ferret is a jill. A spayed female is a sprite, a neutered male is a gib, and a vasectomised male is known as a hoblet. Ferrets under one year old are known as kits. A group of ferrets is known as a "business",[4] or historically as a "busyness". Other purported collective nouns, including "besyness", "fesynes", "fesnyng" and "feamyng", appear in some dictionaries, but are almost certainly ghost words.[5]

 

Biology

 

Skull of a ferret

Characteristics

 

Ferret profile

Ferrets have a typical mustelid body-shape, being long and slender. Their average length is about 50 cm (20 in) including a 13 cm (5.1 in) tail. Their pelage has various colorations including brown, black, white or mixed. They weigh between 0.7 and 2.0 kg (1.5 and 4.4 lb) and are sexually dimorphic as the males are substantially larger than females. The average gestation period is 42 days and females may have two or three litters each year. The litter size is usually between three and seven kits which are weaned after three to six weeks and become independent at three months. They become sexually mature at approximately 6 months and the average life span is 7 to 10 years.[6][7] Ferrets are induced ovulators.[8]

 

Behavior

Ferrets spend 14–18 hours a day asleep and are most active around the hours of dawn and dusk, meaning they are crepuscular.[9] If they are caged, they should be taken out daily to exercise and satisfy their curiosity; they need at least an hour and a place to play.[10] Unlike their polecat ancestors, which are solitary animals, most ferrets will live happily in social groups. They are territorial, like to burrow, and prefer to sleep in an enclosed area.[11]

 

Like many other mustelids, ferrets have scent glands near their anus, the secretions from which are used in scent marking. Ferrets can recognize individuals from these anal gland secretions, as well as the sex of unfamiliar individuals.[12] Ferrets may also use urine marking for sex and individual recognition.[13]

 

As with skunks, ferrets can release their anal gland secretions when startled or scared, but the smell is much less potent and dissipates rapidly. Most pet ferrets in the US are sold descented (with the anal glands removed).[14] In many other parts of the world, including the UK and other European countries, de-scenting is considered an unnecessary mutilation.

 

If excited, they may perform a behavior called the "weasel war dance", characterized by frenzied sideways hops, leaps and bumping into nearby objects. Despite its common name, it is not aggressive but is a joyful invitation to play. It is often accompanied by a unique soft clucking noise, commonly referred to as "dooking".[15] When scared, ferrets will hiss; when upset, they squeak softly.[16]

 

Diet

Ferrets are obligate carnivores.[17] The natural diet of their wild ancestors consisted of whole small prey, including meat, organs, bones, skin, feathers and fur.[18] Ferrets have short digestive systems and a quick metabolism, so they need to eat frequently. Prepared dry foods consisting almost entirely of meat (including high-grade cat food, although specialized ferret food is increasingly available and preferable)[19] provide the most nutritional value. Some ferret owners feed pre-killed or live prey (such as mice and rabbits) to their ferrets to more closely mimic their natural diet.[20][21] Ferret digestive tracts lack a cecum and the animal is largely unable to digest plant matter.[22] Before much was known about ferret physiology, many breeders and pet stores recommended food like fruit in the ferret diet, but it is now known that such foods are inappropriate, and may in fact have negative consequences for ferret health. Ferrets imprint on their food at around six months old. This can make introducing new foods to an older ferret a challenge, and even simply changing brands of kibble may meet with resistance from a ferret that has never eaten the food as a kit. It is therefore advisable to expose young ferrets to as many different types and flavors of appropriate food as possible.[23]

 

Dentition

 

Ferret dentition

Ferrets have four types of teeth (the number includes maxillary (upper) and mandibular (lower) teeth) with a dental formula of

3.1.4.1

3.1.4.2

:

 

Twelve small incisor teeth (only 2–3 mm [3⁄32–1⁄8 in] long) located between the canines in the front of the mouth. These are used for grooming.

Four canines used for killing prey.

Twelve premolar teeth that the ferret uses to chew food—located at the sides of the mouth, directly behind the canines. The ferret uses these teeth to cut through flesh, using them in a scissors action to cut the meat into digestible chunks.

Six molars (two on top and four on the bottom) at the far back of the mouth are used to crush food.

Health

 

Male ferret

Ferrets are known to suffer from several distinct health problems. Among the most common are cancers affecting the adrenal glands, pancreas and lymphatic system.

 

Adrenal disease, a growth of the adrenal glands that can be either hyperplasia or cancer, is most often diagnosed by signs like unusual hair loss, increased aggression, and difficulty urinating or defecating. Treatment options include surgery to excise the affected glands, melatonin or deslorelin implants, and hormone therapy. The causes of adrenal disease speculated to include unnatural light cycles, diets based around processed ferret foods, and prepubescent neutering. It has also been suggested that there may be a hereditary component to adrenal disease.[24]

 

Insulinoma, a type of cancer of the islet cells of the pancreas, is the most common form of cancer in ferrets. It is most common in ferrets between the ages of 4 and 5 years old.[25]

 

Lymphoma is the most common malignancy in ferrets. Ferret lymphosarcoma occurs in two forms—juvenile lymphosarcoma, a fast-growing type that affects ferrets younger than two years, and adult lymphosarcoma, a slower-growing form that affects ferrets four to seven years old.[26]

 

Viral diseases include canine distemper, influenza and ferret systemic coronavirus.[27][28][29]

 

A high proportion of ferrets with white markings which form coat patterns known as a blaze, badger, or panda coat, such as a stripe extending from their face down the back of their head to their shoulder blades, or a fully white head, have a congenital deafness (partial or total) which is similar to Waardenburg syndrome in humans.[30] Ferrets without white markings, but with premature graying of the coat, are also more likely to have some deafness than ferrets with solid coat colors which do not show this trait.[31] Most albino ferrets are not deaf; if deafness does occur in an albino ferret, this may be due to an underlying white coat pattern which is obscured by the albinism.[30]

 

Health problems can occur in unspayed females when not being used for breeding.[32] Similar to domestic cats, ferrets can also suffer from hairballs and dental problems. Ferrets will also often chew on and swallow foreign objects which can lead to bowel obstruction.[33]

 

History of domestication

 

Women hunting rabbits with a ferret in the 14th-century Queen Mary Psalter

In common with most domestic animals, the original reason for ferrets being domesticated by human beings is uncertain, but it may have involved hunting. According to phylogenetic studies, the ferret was domesticated from the European polecat (Mustela putorius), and likely descends from a North African lineage of the species.[34] Analysis of mitochondrial DNA suggests that ferrets were domesticated around 2,500 years ago. It has been claimed that the ancient Egyptians were the first to domesticate ferrets, but as no mummified remains of a ferret have yet been found, nor any hieroglyph of a ferret, and no polecat now occurs wild in the area, that idea seems unlikely.[35] The American Society of Mammalogists classifies M. furo as a distinct species.[36]

 

Ferrets were probably used by the Romans for hunting.[37][38] Genghis Khan, ruler of the Mongol Empire, is recorded as using ferrets in a gigantic hunt in 1221 that aimed to purge an entire region of wild animals.[3]

 

Colonies of feral ferrets have established themselves in areas where there is no competition from similarly sized predators, such as in the Shetland Islands and in remote regions in New Zealand. Where ferrets coexist with polecats, hybridization is common. It has been claimed that New Zealand has the world's largest feral population of ferret–polecat hybrids.[39] In 1877, farmers in New Zealand demanded that ferrets be introduced into the country to control the rabbit population, which was also introduced by humans. Five ferrets were imported in 1879, and in 1882–1883, 32 shipments of ferrets were made from London, totaling 1,217 animals. Only 678 landed, and 198 were sent from Melbourne, Australia. On the voyage, the ferrets were mated with the European polecat, creating a number of hybrids that were capable of surviving in the wild. In 1884 and 1886, close to 4,000 ferrets and ferret hybrids, 3,099 weasels and 137 stoats were turned loose.[40] Concern was raised that these animals would eventually prey on indigenous wildlife once rabbit populations dropped, and this is exactly what happened to New Zealand's bird species which previously had had no mammalian predators.

 

Ferreting

Main article: Rabbiting

 

Muzzled ferret flushing a rat, as illustrated in Harding's Ferret Facts and Fancies (1915)

For millennia, the main use of ferrets was for hunting, or "ferreting". With their long, lean build and inquisitive nature, ferrets are very well equipped for getting down holes and chasing rodents, rabbits and moles out of their burrows. The Roman historians Pliny and Strabo record that Caesar Augustus sent "viverrae" from Libya to the Balearic Islands to control rabbit plagues there in 6 BC; it is speculated that "viverrae" could refer to ferrets, mongooses, or polecats.[3][41][42] In England, in 1390, a law was enacted restricting the use of ferrets for hunting to the relatively wealthy:

 

it is ordained that no manner of layman which hath not lands to the value of forty shillings a year shall from henceforth keep any greyhound or other dog to hunt, nor shall he use ferrets, nets, heys, harepipes nor cords, nor other engines for to take or destroy deer, hares, nor conies, nor other gentlemen's game, under pain of twelve months' imprisonment.[43]

 

Ferrets were first introduced into the American continents in the 17th century, and were used extensively from 1860 until the start of World War II to protect grain stores in the American West from rodents. They are still used for hunting in some countries, including the United Kingdom, where rabbits are considered a pest by farmers.[44] The practice is illegal in several countries where it is feared that ferrets could unbalance the ecology. In 2009 in Finland, where ferreting was previously unknown, the city of Helsinki began to use ferrets to restrict the city's rabbit population to a manageable level. Ferreting was chosen because in populated areas it is considered to be safer and less ecologically damaging than shooting the rabbits.

 

As pets

 

A ferret in a war dance jump

In the United States, ferrets were relatively rare pets until the 1980s. A government study by the California State Bird and Mammal Conservation Program estimated that by 1996 about 800,000 domestic ferrets were being kept as pets in the United States.[45]

 

Regulation

Australia: It is illegal to keep ferrets as pets in Queensland and the Northern Territory;[46] in the Australian Capital Territory a licence is required.[47]

Brazil: Ferrets are allowed only if they are given a microchip identification tag and sterilized.

New Zealand: It has been illegal to sell, distribute or breed ferrets in New Zealand since 2002 unless certain conditions are met.[48]

United States: Ferrets were once banned in many US states, but most of these laws were rescinded in the 1980s and 1990s as they became popular pets.

Illegal: Ferrets are illegal in California under Fish and Game Code Section 2118;[49] and the California Code of Regulations,[50] although it is not illegal for veterinarians in the state to treat ferrets kept as pets. "Ferrets are strictly prohibited as pets under Hawaii law because they are potential carriers of the rabies virus";[51] the territory of Puerto Rico has a similar law.[52] Ferrets are restricted by some municipalities, such as New York City,[52] which renewed its ban in 2015.[53][54] They are also prohibited on many military bases.[52] A permit to own a ferret is needed in other areas, including Rhode Island.[55] Illinois and Georgia do not require a permit to merely possess a ferret, but a permit is required to breed ferrets.[56][57] It was once illegal to own ferrets in Dallas, Texas,[58] but the current Dallas City Code for Animals includes regulations for the vaccination of ferrets.[59] Pet ferrets are legal in Wisconsin, however legality varies by municipality. The city of Oshkosh, Wisconsin, for example, classifies ferrets as a wild animal and subsequently prohibits them from being kept within the city limits. Also, an import permit from the state department of agriculture is required to bring one into the state.[60] Under common law, ferrets are deemed "wild animals" subject to strict liability for injuries they cause, but in several states statutory law has overruled the common law, deeming ferrets "domestic".[61]

Japan: In Hokkaido prefecture, ferrets must be registered with the local government.[62] In other prefectures, no restrictions apply.

Other uses

Ferrets are an important experimental animal model for human influenza,[63][64] and have been used to study the 2009 H1N1 (swine flu) virus.[65] Smith, Andrews, Laidlaw (1933) inoculated ferrets intra-nasally with human naso-pharyngeal washes, which produced a form of influenza that spread to other cage mates. The human influenza virus (Influenza type A) was transmitted from an infected ferret to a junior investigator, from whom it was subsequently re-isolated.

 

Ferrets have been used in many broad areas of research, such as the study of pathogenesis and treatment in a variety of human disease, these including studies into cardiovascular disease, nutrition, respiratory diseases such as SARS and human influenza, airway physiology,[66] cystic fibrosis and gastrointestinal disease.

Because they share many anatomical and physiological features with humans, ferrets are extensively used as experimental subjects in biomedical research, in fields such as virology, reproductive physiology, anatomy, endocrinology and neuroscience.[67]

In the UK, ferret racing is often a feature of rural fairs or festivals, with people placing small bets on ferrets that run set routes through pipes and wire mesh. Although financial bets are placed, the event is primarily for entertainment purposes as opposed to 'serious' betting sports such as horse or greyhound racing.[68][69]

A very small experimental study of ferrets found that a nasal spray effectively blocked the transmission of the SARS-CoV-2 coronavirus that causes COVID-19.[70]

Terminology and coloring

 

Typical ferret coloration, known as a sable or polecat-colored ferret

Most ferrets are either albinos, with white fur and pink eyes, or display the typical dark masked sable coloration of their wild polecat ancestors. In recent years fancy breeders have produced a wide variety of colors and patterns. Color refers to the color of the ferret's guard hairs, undercoat, eyes and nose; pattern refers to the concentration and distribution of color on the body, mask and nose, as well as white markings on the head or feet when present. Some national organizations, such as the American Ferret Association, have attempted to classify these variations in their showing standards.[71]

 

There are four basic colors. The sable (including chocolate and dark brown), albino, dark-eyed white (DEW, also known as black-eyed white or BEW) and silver. All the other colors of a ferret are variations on one of these four categories.

 

Waardenburg-like coloring

 

White or albino ferret

Ferrets with a white stripe on their face or a fully white head, primarily blazes, badgers and pandas, almost certainly carry a congenital defect which shares some similarities to Waardenburg syndrome. This causes, among other things, a cranial deformation in the womb which broadens the skull, white face markings, and also partial or total deafness. It is estimated as many as 75 percent of ferrets with these Waardenburg-like colorings are deaf.

 

White ferrets were favored in the Middle Ages for the ease in seeing them in thick undergrowth. Leonardo da Vinci's painting Lady with an Ermine is likely mislabelled; the animal is probably a ferret, not a stoat (for which "ermine" is an alternative name for the animal in its white winter coat). Similarly, the ermine portrait of Queen Elizabeth I shows her with her pet ferret, which has been decorated with painted-on heraldic ermine spots.

 

The Ferreter's Tapestry is a 15th-century tapestry from Burgundy, France, now part of the Burrell Collection housed in the Glasgow Museum and Art Galleries. It shows a group of peasants hunting rabbits with nets and white ferrets. This image was reproduced in Renaissance Dress in Italy 1400–1500, by Jacqueline Herald, Bell & Hyman.[72]

 

Gaston Phoebus' Book of the Hunt was written in approximately 1389 to explain how to hunt different kinds of animals, including how to use ferrets to hunt rabbits. Illustrations show how multicolored ferrets that were fitted with muzzles were used to chase rabbits out of their warrens and into waiting nets.

 

Import restrictions

Australia – Ferrets cannot be imported into Australia. A report drafted in August 2000 seems to be the only effort made to date to change the situation.[73]

Canada – Ferrets brought from anywhere except the US require a Permit to Import from the Canadian Food Inspection Agency Animal Health Office. Ferrets from the US require only a vaccination certificate signed by a veterinarian. Ferrets under three months old are not subject to any import restrictions.[74]

European Union – As of July 2004, dogs, cats and ferrets can travel freely within the European Union under the pet passport scheme. To cross a border within the EU, ferrets require at minimum an EU PETS passport and an identification microchip (though some countries will accept a tattoo instead). Vaccinations are required; most countries require a rabies vaccine, and some require a distemper vaccine and treatment for ticks and fleas 24 to 48 hours before entry. Ferrets occasionally need to be quarantined before entering the country. PETS travel information is available from any EU veterinarian or on government websites.

New Zealand – New Zealand has banned the import of ferrets into the country.[75]

United Kingdom – The UK accepts ferrets under the EU's PETS travel scheme. Ferrets must be microchipped, vaccinated against rabies, and documented. They must be treated for ticks and tapeworms 24 to 48 hours before entry. They must also arrive via an authorized route. Ferrets arriving from outside the EU may be subject to a six-month quarantine

The Pokhot live in the Baringo and Western Pokot districts of Kenya and in Uganda.

There are two main sub-groups depending of their location and way of life. The first group consist of the Hill Pokot who live in the rainy highlands in the west and in the central south, and are mainly farmers and pastoralists. The second group is made up of the Plains Pokot who live in dry and infertile plains, with their cattles. A homestead is composed of one or more buildings for a man, his wife and children; eventual co-wives live in separate houses. The role of the community in teaching children ethical rules. Most of the Pokot are nomadic and thus have interacted with different peoples, incorporating their social customs.The Pokot are very proud of their culture. The Songs, storytelling, and decorative arts, especially bodily decoration, are very appreciated. They adorn the body with beads, hairstyling, scarification, and the removal of the lower central incisors. Pokot girls wear a beaded necklace made of the stems of an asparagus tree. Most Pokot have some knowledge of herbal medicine, so they often use these treatments along with those of the hospitals. They belong to the Kenya's Nilotic-speaking peoples. .

For the Pokot, the universe has two realms: the above is the realm of the most powerful deities—Tororot, Asis (sun), and llat (rain); and the below is the one where live humans, animals, and plants. Humans are responsible for the realm that they inhabit, but they rely upon divinities to achieve and maintain peace and prosperity. They worship many deities like the sun, moon and believe in the spirit of death.The Pokot communicate with their deities through prayer and sacrifice. They perform it during ethnic festivals and dances. Oracles are responsible for maintaining the spiritual balance within the community. They are superstitious and believe in sorcery, so sometimes they call on shielding lucky sorcery. They have prophets, either male or female, who foresee advise, usually by the means of animal sacrifices. His or her ability is considered as a divine gift. Clan histories recount the changes of location, through poetry and song, emphasizing the vulnerability of humans and the importance of supernatural powers to help them overcome hunger, thirst, and even death. Ceremonies mark the transitions in the people's social lives. Among these are: the cleansing of a couple expecting their first child; the cleansing of newborn infants and their mothers; the cleansing of twins and other children who are born under unusual circumstances; male and female initiation; marriage; sapana, a coming-of-age ceremony for men; and summer-solstice, harvest, and healing ceremonies. The most important rite of passage for most Pokot is circumcision for boys and clitoridectomy for girls. These rites consist of a series of neighborhood-based ceremonies, emphasizing the importance of having a good behavior. When boys are circumcised, they acquire membership in one of eight age sets. Women do not have age-sets. After excisions, for several months, girls have a white painting on their face and wear a hood made of blackened leather with charcoal and oil. This means they are untouchable until the lepan ceremony, that marks the passage to womanhood. Unlike other tribes, the Pokot keep the affiliation to their clan throughout their lives, there is no disruption with marriage. Surprisingly, the agreement before marriage is made by gift giving, from the groom and his family to the bride and her family, often over a period of years (and not the contrary). It often implies the gift of a combination of livestock, goods, and cash to the bride's family, and the allotment of milk cows and rights to land to the bride. The bond between a husband and wife lasts for 3 generations, after what marriages can take place again between the two groups. Polygamy exists but is not prevalent among men before 40. The spirits of the elder anticipate reincarnation in their living descendants: when a child is said to resemble the elder, the same name is given. Disputes are resolved in neighborhood councils and in government courts. Some of the sanctions include shaming, cursing, and bewitching.

 

© Eric Lafforgue

www.ericlafforgue.com

      

Black-tailed buck. Deer are ruminants, which means they have a four-chambered stomach, chew a cud, and regurgitate food more than once before finally swallowing it. They also have canine teeth and upper incisors that are reduced or missing. IMG_3618

The brown bear (Ursus arctos) is a large bear distributed across much of northern Eurasia and North America. It can weigh from 300 to 780 kilograms (660 to 1720 lbs) and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family[2] and as the largest land-based predator.[3]

 

There are several recognized subspecies within the brown bear species. In North America, two types are generally recognized, the coastal brown bear and the inland grizzly, and the two types could broadly define all brown bear subspecies. Grizzlies weigh as little as 350 lb (159 kg) in Yukon, while a brown bear, living on a steady, nutritious diet of spawning salmon, from Coastal Alaska and Russia can weigh 1500 lb (682 kg). The exact number of overall brown subspecies remains in debate.

 

While the brown bear's range has shrunk, and it has faced local extinctions, it remains listed as a least concern species by the IUCN, with a total population of approximately 200,000. Its principal range countries are Russia, the United States (mostly in Alaska), Canada, the Carpathian region (especially Romania), and Finland where it is the national animal. The brown bear is the most widely distributed of all bears.

Brown bears are thought to have evolved from Ursus etruscus. The oldest fossils occur in China from about 0.5 million years ago. They entered Europe about 250,000 years ago, and North Africa shortly after. Brown bear remains from the Pleistocene period are common in the British Isles, where it is thought they outcompeted cave bears. The species entered Alaska 100,000 years ago, though they did not move south until 13,000 years ago.[6] It is thought that brown bears were unable to migrate south until the extinction of the much larger Arctodus simus.[7] Several paleontologists suggest the possibility of two separate brown bear migrations: grizzlies are thought to stem from narrow-skulled bears which migrated from northern Siberia to central Alaska and the rest of the continent, while Kodiak bears descend from broad-skulled bears from Kamchatka which colonised the Alaskan peninsula. Brown bear fossils discovered in Ontario, Ohio, Kentucky and Labrador show that the species occurred farther east than indicated in historic records.[6]Brown bears are massively built and heavy bodied animals. They have a large hump-like mass of muscle on their shoulders, which coupled with their long claws, provide brown bears with a great digging ability.[15] Brown bears have very large and curved claws, those present on the forelimbs being longer than those on the hind limbs. They may reach 5 to 6 centimetres (2.0 to 2.4 in) and sometimes 7 to 10 centimetres (2.8 to 3.9 in) along the curve.[11] They are never less than 6 centimetres (2.4 in) in length.[15] They are generally dark with a light tip with some forms having completely light claws.[11] Brown bear claws are longer and straighter than those of American black bears.[15] The claws are blunt, while those of a black bear are sharp.

 

Adults have massive, heavily built concave skulls which are large in proportion to the body. The forehead is high and rises steeply.[15] The projections of the skull are well developed when compared to those of Asian black bears: the latter have sagittal crests not exceeding more than 19–20% of the total length of the skull, while the former have sagittal crests comprising up to 40–41% of the skull's length. Skull projections are more weakly developed in female brown bears than in males. The braincase is relatively small and elongated. There is a great deal of geographical variation in the skull, and presents itself chiefly in dimensions.[11] Grizzlies, for example, tend to have flatter profiles than European and coastal American brown bears.[16] Skull lengths of Russian bears tend to be 31.5 to 45.5 centimetres (12.4 to 17.9 in) for males, and 27.5 to 39.7 centimetres (10.8 to 15.6 in) for females. The width of the zygomatic arches in males is 17.5 to 27.7 centimetres (6.9 to 11 in), and 14.7 to 24.7 centimetres (5.8 to 9.7 in) in females.[11] Brown bears have very strong teeth: the incisors are relatively big and the canine teeth are large, the lower ones being strongly curved. The first three molars of the upper jaw are underdeveloped and single crowned with one root. The second upper molar is smaller than the others, and is usually absent in adults. It is usually lost at an early age, leaving no trace of the alveolus in the jaw. The first three molars of the lower jaw are very weak, and are often lost at an early age.[11] Although they have powerful jaws, brown bear jaws are incapable of breaking large bones with the ease of spotted hyenas.[17]

 

The dimensions of brown bears fluctuate very greatly according to sex, age, individual, geographic location, and season. The normal range of physical dimensions for a brown bear is a head-and-body length of 1.7 to 2.8 meters (5.6 to 9.2 ft) and a shoulder height of 90 to 150 centimeters (35–60 in). The smallest subspecies is the Eurasian Brown Bear whose mature females weigh as little as 90 kg (200 lb).[18] Barely larger, Grizzly Bears from the Yukon region (which are a third smaller than most grizzlies) can weigh as little as 100 kg (220 lb) in the spring[19] and the Syrian Brown Bear, with mature females weighing as little as 150 kg (330 lb). The largest subspecies are the Kodiak Bear, Siberian Brown Bear, and the bears from coastal Russia and Alaska. It is not unusual for large male Kodiak Bears to stand over 3 m (9.8 ft) while on their hind legs, and to weigh up to 680 kg (1,500 lb).[20] The heaviest recorded brown bear weighed over 1,150 kilograms

There are about 200,000 brown bears in the world. The largest populations are in Russia with 120,000, the United States with 32,500, and Canada with 21,750. 95% of the brown bear population in the United States is in Alaska, though in the lower 48 states they are repopulating slowly but steadily along the Rockies and the Western Great plains. Although many people hold on to the belief that some brown bears may be present in Mexico and the Atlas Mountains of Morocco, both are almost certainly extinct. The last Mexican brown bear was shot in 1960. In Europe, there are 14,000 brown bears in ten fragmented populations, from Spain in the west, to Russia in the east, and from Scandinavia in the north to Romania(4000–5000), Bulgaria (900–1200), Slovakia (with about 600–800 animals), and Greece (with about 200 animals) in the south. They are extinct in the British Isles, extremely threatened in France and Spain, and in trouble over most of Central Europe. The Carpathian brown bear population of Romania is the largest in Europe outside Russia, estimated at 4,500 to 5,000 bears. Scandinavia is home to a large bear population, with an estimated 2,500 (range 2,350–2,900) in Sweden, 900–1300 in Finland,[21] and 70 in Norway. Another large and relatively stable population of brown bears in Europe, consisting of 2,500–3,000 individuals, is the Dinaric-Pindos (Balkans) population, with contiguous distribution in north-east Italy, Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, Macedonia, Albania, Bulgaria and Greece.[22]

 

Brown bears were once native to Asia, the Atlas Mountains in Africa, Europe, and North America,[23] but are now extinct in some areas and their populations have greatly decreased in other areas. They prefer semi-open country, usually in mountainous areas.

 

Brown bears live in Alaska, east through the Yukon and Northwest Territories, south through British Columbia and through the western half of Alberta. Small populations exist in the Greater Yellowstone Ecosystem of northwest Wyoming (with about 600 animals), the Northern Continental Divide Ecosystem of northwest Montana (with about 750 animals), the Cabinet-Yaak Ecosystem of northwest Montana and northeast Idaho (with about 30–40 animals), the Selkirk Ecosystem of northeast Washington and northwest Idaho (with about 40–50 animals), and the North Cascades Ecosystem of north-central Washington (with about 5–10 animals). These five ecosystems combine for a total of roughly 1,470 wild grizzlies still persisting in the contiguous United States. Unfortunately, these populations are isolated from each other, inhibiting any genetic flow to occur between ecosystems. This poses one of the greatest threats to the future survival of the grizzly bear in the contiguous United States.

 

In Asia, brown bears are found in most of Russia, parts of the Middle East, and in a little bit of Manchuria in China. They can also be found on the island of Hokkaidō in Japan and in Western China and a little bit of Afghanistan, Pakistan, and India.

 

The population of brown bears in the Pyrenees mountain range between France and Spain is so low, estimated at 14 to 18 with a shortage of females, that bears, mostly female, from Slovenia were released in spring 2006 to reduce the imbalance and preserve the species' presence in the area, despite protests from French farmers.

 

A small population of brown bears (Ursus arctos marsicanus) still lives in central Italy (Apennine mountains, Abruzzo and Latium) with no more than 70 individuals, protected by strong laws but endangered by the human presence in the area.

 

In Arctic areas, the potential habitat of the brown bear is increasing. The warming of that region has allowed the species to move farther north into what was once exclusively the domain of the polar bear. In non-Arctic areas, habitat loss is blamed as the leading cause of endangerment, followed by hunting.

 

North American brown bears seem to prefer open landscapes, whereas in Eurasia they inhabit mostly dense forests. It is thought that the Eurasian bears which colonized America were tundra-adapted. This is indicated by brown bears in the Chukotka Peninsula on the Asian side of Bering Strait, which are the only Asian brown bears to live year-round in lowland tundra like their North American cousins.[24]

The brown bear is primarily nocturnal. In the summer, it gains up to 180 kilograms (400 lb) of fat, on which it relies to make it through winter, when it becomes very lethargic. Although they are not full hibernators, and can be woken easily, both sexes like to den in a protected spot such as a cave, crevice, or hollow log during the winter months. Brown bears are mostly solitary, although they may gather in large numbers at major food sources and form social hierarchies based on age and size.[25] Adult male bears are particularly aggressive and are avoided by adolescent and subadult males. Female bears with cubs rival adult males in aggression and more intolerant of other bears than single females. Young adolescent males tend to be least aggressive and have been observed making non-agonistic interactions with each other. In his Great Bear Almanac, Gary Brown lists 11 different sounds bears produce in 9 different contexts. Sounds expressing anger or aggravation include growls, roars, woofs, champs and smacks while sounds expressing nervousness or pain include woofs, grunts and bawls. Sows will bleat or hum when communicating with their cubs.[15]The mating season is from late May to early July. Being serially monogamous, brown bears remain with the same mate from several days to a couple of weeks.[26] Females mature sexually between the age of 5 and 7 years, while males usually mate a few years later when they are large and strong enough to successfully compete with other males for mating rights.Males however take no part in raising their cubs – parenting is left entirely to the females.

 

Through the process of delayed implantation, a female's fertilized egg divides and floats free in the uterus for six months. During winter dormancy, the fetus attaches to the uterine wall. The cubs are born eight weeks later, while the mother sleeps. If the mother does not gain enough weight to survive through the winter, the embryo does not implant and is reabsorbed into the body. The average litter has one to four cubs, usually two. There have been cases of bears with five cubs, although females sometimes adopt strange cubs. Older females tend to give birth to larger litters. The size of a litter also depends on factors such as geographic location and food supply. At birth, the cubs are blind, toothless, hairless, and weigh less than 450 grams (1.0 lb). They feed on their mother's milk until spring or even early summer depending on climate conditions. At this time, the cubs weigh 7 to 9 kilograms (15 to 20 lb) and have developed enough to follow her and begin to forage for solid food.

 

Cubs remain with their mother from two to four years, during which time they learn survival techniques, such as which foods have the highest nutritional values and where to obtain them; how to hunt, fish, and defend themselves; and where to den. The cubs learn by following and imitating their mother's actions during the period they are with her.[27] Brown bears practice infanticide.[28] An adult male bear may kill the cubs of another bear either to make the female sexually receptive or simply for consumption. Cubs flee up a tree when they see a strange male bear, and the mother defends them even though the male may be twice her size.

They are omnivores and feed on a variety of plant products, including berries, roots, and sprouts, fungi as well as meat products such as fish, insects, and small mammals. Despite their reputation, most brown bears are not highly carnivorous as they derive up to 90% of their dietary food energy from vegetable matter.[29] Their jaw structure has evolved to fit their dietary habits. Their diet varies enormously throughout their differing areas based on opportunity. For example, bears in Yellowstone eat an enormous number of moths during the summer, sometimes as many as 40,000 in a day, and may derive up to half of their annual food energy from these insects.[30] In some areas of Russia and Alaska, brown bears feed mostly on spawning salmon, whose nutrition and abundance explain the enormous size of the bears in these areas. Brown bears also occasionally prey on large mammals, such as deer, elk, moose, caribou, bighorn sheep, mountain goats, bison and muskoxen. When brown bears attack these animals, they tend to choose the young ones as they are easier to catch. When hunting, the bear pins its prey to the ground and then tears and eats it alive.[31] On rare occasions, bears kill by hitting their prey with their powerful forearms which can break the necks and backs of large prey, such as moose. They also feed on carrion and use their size to intimidate other predators such as wolves, cougars, tigers, and black bears from their kills.

Attacks on humans

As a rule, brown bears seldom attack humans on sight, and usually avoid people. They are however unpredictable in temperament, and will attack if they are surprised or feel threatened.[51] Sows with cubs account for the majority of injuries and fatalities in North America. Habituated or food-conditioned bears can also be dangerous, as their long-term exposure to humans causes them to lose their natural shyness, and in some cases associate humans with food. Small parties of one or two people are more often attacked than large groups, with no attacks being recorded against parties of six people or more. In contrast to injuries caused by American black bears, which are usually minor, brown bear attacks tend to result in serious injury and in some cases death.[51] In the majority of attacks resulting in injury, brown bears precede the attack with a growl or huffing sound[51], and seem to confront humans as they would when fighting other bears: they rise up on their hind legs, and attempt to "disarm" their victims by biting and holding on to the lower jaw to avoid being bitten in turn.[7] Such a bite can be as severe as that of a tiger, with some human victims having had their heads completely crushed by a bear bite.[16] Most attacks occur in the months of July, August and September, the time when the number of outdoor recreationalists, such as hikers or hunters, is higher. People who assert their presence through noises tend to be less vulnerable, as they alert bears to their presence. In direct confrontations, people who run are statistically more likely to be attacked than those who stand their ground. Violent encounters with brown bears usually last only a few minutes, though they can be prolonged if the victims fight back.[51]

 

Attacks on humans are considered extremely rare in the former Soviet Union, though exceptions exist in districts where they are not pursued by hunters.[11] Siberian bears for example tend to be much bolder toward humans than their shyer, more persecuted European counterparts.[52] In 2008, a platinum mining compound in the Olyotorsky district of northern Kamchatka was besieged by a group of 30 bears who killed two guards and prevented workers from leaving their homes.[53] Ten people a year are killed by brown bears in Russia.[54] In Scandinavia, only three fatal attacks were recorded in the 20th century.[55]

 

In Japan, a large brown bear nicknamed "Kesagake" (袈裟懸け, "kesa-style slasher") made history for causing the worst bear attack in Japanese history at Tomamae, Hokkaidō during December, 1915, killing 7 people (including 1 pregnant woman) and wounding 3 others (with possible another 3 previous fatalities to its credits) before being gunned down after a large-scale beast-hunt. Today, there is still a shrine at Rokusensawa (六線沢), where the event took place, in memory of the victims of the incident.

 

Native American tribes sympatric to brown bears often viewed them with a mixture of awe and fear. North American brown bears were so feared by the Natives that they were rarely hunted, especially alone. When Natives hunted grizzlies, the act was done with the same preparation and ceremoniality as intertribal warfare, and was never done except with a company of 4–10 warriors. The tribe members who dealt the killing blow were highly esteemed among their compatriots. Californian Indians actively avoided prime bear habitat, and would not allow their young men to hunt alone, for fear of bear attacks. During the Spanish colonial period, some tribes, instead of hunting grizzlies themselves, would seek aid from European colonists to deal with problem bears. Many authors in the American west wrote of Natives or voyagers with lacerated faces and missing noses or eyes due to attacks from grizzlies.[7] Within Yellowstone National Park, injuries caused by grizzly attacks in developed areas averaged approximately 1 per year during the 1930s through to the 1950s, though it increased to 4 per year during the 1960s. They then decreased to 1 injury every 2 years (0.5/year) during the 1970s. Between 1980 and 2002, there have been only 2 human injuries caused by grizzly bears in a developed area. However, although grizzly attacks were rare in the backcountry before 1970, the number of attacks increased to an average of approximately 1 per year during the 1970s, 1980s, and 1990s.[56]

 

History of defense from bears

The horse (Equus caballus) is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of Equus ferus. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, close to Eohippus, into the large, single-toed animal of today. Humans began domesticating horses around 4000 BCE, and their domestication is believed to have been widespread by 3000 BCE. Horses in the subspecies caballus are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, which are horses that never have been domesticated. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior.

 

Horses are adapted to run, allowing them to quickly escape predators, and possess an excellent sense of balance and a strong fight-or-flight response. Related to this need to flee from predators in the wild is an unusual trait: horses are able to sleep both standing up and lying down, with younger horses tending to sleep significantly more than adults. Female horses, called mares, carry their young for approximately 11 months and a young horse, called a foal, can stand and run shortly following birth. Most domesticated horses begin training under a saddle or in a harness between the ages of two and four. They reach full adult development by age five, and have an average lifespan of between 25 and 30 years.

 

Horse breeds are loosely divided into three categories based on general temperament: spirited "hot bloods" with speed and endurance; "cold bloods", such as draft horses and some ponies, suitable for slow, heavy work; and "warmbloods", developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe. There are more than 300 breeds of horse in the world today, developed for many different uses.

 

Horses and humans interact in a wide variety of sport competitions and non-competitive recreational pursuits as well as in working activities such as police work, agriculture, entertainment, and therapy. Horses were historically used in warfare, from which a wide variety of riding and driving techniques developed, using many different styles of equipment and methods of control. Many products are derived from horses, including meat, milk, hide, hair, bone, and pharmaceuticals extracted from the urine of pregnant mares. Humans provide domesticated horses with food, water, and shelter, as well as attention from specialists such as veterinarians and farriers.

 

Lifespan and life stages

Depending on breed, management and environment, the modern domestic horse has a life expectancy of 25 to 30 years. Uncommonly, a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was "Old Billy", a 19th-century horse that lived to the age of 62. In modern times, Sugar Puff, who had been listed in Guinness World Records as the world's oldest living pony, died in 2007 at age 56.

 

Regardless of a horse or pony's actual birth date, for most competition purposes a year is added to its age each January 1 of each year in the Northern Hemisphere and each August 1 in the Southern Hemisphere. The exception is in endurance riding, where the minimum age to compete is based on the animal's actual calendar age.

 

The following terminology is used to describe horses of various ages:

 

Foal

A horse of either sex less than one year old. A nursing foal is sometimes called a suckling, and a foal that has been weaned is called a weanling. Most domesticated foals are weaned at five to seven months of age, although foals can be weaned at four months with no adverse physical effects.

Yearling

A horse of either sex that is between one and two years old.

Colt

A male horse under the age of four. A common terminology error is to call any young horse a "colt", when the term actually only refers to young male horses.

Filly

A female horse under the age of four.

Mare

A female horse four years old and older.

Stallion

A non-castrated male horse four years old and older.The term "horse" is sometimes used colloquially to refer specifically to a stallion.

Gelding

A castrated male horse of any age.

In horse racing, these definitions may differ: For example, in the British Isles, Thoroughbred horse racing defines colts and fillies as less than five years old. However, Australian Thoroughbred racing defines colts and fillies as less than four years old.

 

Size and measurement

The height of horses is measured at the highest point of the withers, where the neck meets the back. This point is used because it is a stable point of the anatomy, unlike the head or neck, which move up and down in relation to the body of the horse.

 

Size varies greatly among horse breeds, as with this full-sized horse and small pony.

In English-speaking countries, the height of horses is often stated in units of hands and inches: one hand is equal to 4 inches (101.6 mm). The height is expressed as the number of full hands, followed by a point, then the number of additional inches, and ending with the abbreviation "h" or "hh" (for "hands high"). Thus, a horse described as "15.2 h" is 15 hands plus 2 inches, for a total of 62 inches (157.5 cm) in height.

 

The size of horses varies by breed, but also is influenced by nutrition. Light-riding horses usually range in height from 14 to 16 hands (56 to 64 inches, 142 to 163 cm) and can weigh from 380 to 550 kilograms (840 to 1,210 lb). Larger-riding horses usually start at about 15.2 hands (62 inches, 157 cm) and often are as tall as 17 hands (68 inches, 173 cm), weighing from 500 to 600 kilograms (1,100 to 1,320 lb). Heavy or draft horses are usually at least 16 hands (64 inches, 163 cm) high and can be as tall as 18 hands (72 inches, 183 cm) high. They can weigh from about 700 to 1,000 kilograms (1,540 to 2,200 lb).

 

The largest horse in recorded history was probably a Shire horse named Mammoth, who was born in 1848. He stood 21.2 1⁄4 hands (86.25 inches, 219 cm) high and his peak weight was estimated at 1,524 kilograms (3,360 lb). The record holder for the smallest horse ever is Thumbelina, a fully mature miniature horse affected by dwarfism. She was 43 centimetres; 4.1 hands (17 in) tall and weighed 26 kg (57 lb).

 

Ponies

Main article: Pony

Ponies are taxonomically the same animals as horses. The distinction between a horse and pony is commonly drawn on the basis of height, especially for competition purposes. However, height alone is not dispositive; the difference between horses and ponies may also include aspects of phenotype, including conformation and temperament.

 

The traditional standard for height of a horse or a pony at maturity is 14.2 hands (58 inches, 147 cm). An animal 14.2 hands (58 inches, 147 cm) or over is usually considered to be a horse and one less than 14.2 hands (58 inches, 147 cm) a pony, but there are many exceptions to the traditional standard. In Australia, ponies are considered to be those under 14 hands (56 inches, 142 cm). For competition in the Western division of the United States Equestrian Federation, the cutoff is 14.1 hands (57 inches, 145 cm). The International Federation for Equestrian Sports, the world governing body for horse sport, uses metric measurements and defines a pony as being any horse measuring less than 148 centimetres (58.27 in) at the withers without shoes, which is just over 14.2 hands (58 inches, 147 cm), and 149 centimetres (58.66 in; 14.2+1⁄2 hands), with shoes.

 

Height is not the sole criterion for distinguishing horses from ponies. Breed registries for horses that typically produce individuals both under and over 14.2 hands (58 inches, 147 cm) consider all animals of that breed to be horses regardless of their height. Conversely, some pony breeds may have features in common with horses, and individual animals may occasionally mature at over 14.2 hands (58 inches, 147 cm), but are still considered to be ponies.

 

Ponies often exhibit thicker manes, tails, and overall coat. They also have proportionally shorter legs, wider barrels, heavier bone, shorter and thicker necks, and short heads with broad foreheads. They may have calmer temperaments than horses and also a high level of intelligence that may or may not be used to cooperate with human handlers. Small size, by itself, is not an exclusive determinant. For example, the Shetland pony which averages 10 hands (40 inches, 102 cm), is considered a pony. Conversely, breeds such as the Falabella and other miniature horses, which can be no taller than 76 centimetres; 7.2 hands (30 in), are classified by their registries as very small horses, not ponies.

 

Genetics

Horses have 64 chromosomes. The horse genome was sequenced in 2007. It contains 2.7 billion DNA base pairs, which is larger than the dog genome, but smaller than the human genome or the bovine genome.

 

Colors and markings

Horses exhibit a diverse array of coat colors and distinctive markings, described by a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or sex. Horses of the same color may be distinguished from one another by white markings, which, along with various spotting patterns, are inherited separately from coat color.

 

Many genes that create horse coat colors and patterns have been identified. Current genetic tests can identify at least 13 different alleles influencing coat color, and research continues to discover new genes linked to specific traits. The basic coat colors of chestnut and black are determined by the gene controlled by the Melanocortin 1 receptor, also known as the "extension gene" or "red factor", as its recessive form is "red" (chestnut) and its dominant form is black. Additional genes control suppression of black color to point coloration that results in a bay, spotting patterns such as pinto or leopard, dilution genes such as palomino or dun, as well as greying, and all the other factors that create the many possible coat colors found in horses.

 

Horses that have a white coat color are often mislabeled; a horse that looks "white" is usually a middle-aged or older gray. Grays are born a darker shade, get lighter as they age, but usually keep black skin underneath their white hair coat (with the exception of pink skin under white markings). The only horses properly called white are born with a predominantly white hair coat and pink skin, a fairly rare occurrence. Different and unrelated genetic factors can produce white coat colors in horses, including several different alleles of dominant white and the sabino-1 gene. However, there are no "albino" horses, defined as having both pink skin and red eyes.

 

Reproduction and development

Gestation lasts approximately 340 days, with an average range 320–370 days, and usually results in one foal; twins are rare. Horses are a precocial species, and foals are capable of standing and running within a short time following birth. Foals are usually born in the spring. The estrous cycle of a mare occurs roughly every 19–22 days and occurs from early spring into autumn. Most mares enter an anestrus period during the winter and thus do not cycle in this period. Foals are generally weaned from their mothers between four and six months of age.

 

Horses, particularly colts, are sometimes physically capable of reproduction at about 18 months, but domesticated horses are rarely allowed to breed before the age of three, especially females. Horses four years old are considered mature, although the skeleton normally continues to develop until the age of six; maturation also depends on the horse's size, breed, sex, and quality of care. Larger horses have larger bones; therefore, not only do the bones take longer to form bone tissue, but the epiphyseal plates are larger and take longer to convert from cartilage to bone. These plates convert after the other parts of the bones, and are crucial to development.

 

Depending on maturity, breed, and work expected, horses are usually put under saddle and trained to be ridden between the ages of two and four. Although Thoroughbred race horses are put on the track as young as the age of two in some countries, horses specifically bred for sports such as dressage are generally not put under saddle until they are three or four years old, because their bones and muscles are not solidly developed. For endurance riding competition, horses are not deemed mature enough to compete until they are a full 60 calendar months (five years) old.

 

Anatomy

The horse skeleton averages 205 bones. A significant difference between the horse skeleton and that of a human is the lack of a collarbone—the horse's forelimbs are attached to the spinal column by a powerful set of muscles, tendons, and ligaments that attach the shoulder blade to the torso. The horse's four legs and hooves are also unique structures. Their leg bones are proportioned differently from those of a human. For example, the body part that is called a horse's "knee" is actually made up of the carpal bones that correspond to the human wrist. Similarly, the hock contains bones equivalent to those in the human ankle and heel. The lower leg bones of a horse correspond to the bones of the human hand or foot, and the fetlock (incorrectly called the "ankle") is actually the proximal sesamoid bones between the cannon bones (a single equivalent to the human metacarpal or metatarsal bones) and the proximal phalanges, located where one finds the "knuckles" of a human. A horse also has no muscles in its legs below the knees and hocks, only skin, hair, bone, tendons, ligaments, cartilage, and the assorted specialized tissues that make up the hoof.

 

Hooves

Main articles: Horse hoof, Horseshoe, and Farrier

The critical importance of the feet and legs is summed up by the traditional adage, "no foot, no horse". The horse hoof begins with the distal phalanges, the equivalent of the human fingertip or tip of the toe, surrounded by cartilage and other specialized, blood-rich soft tissues such as the laminae. The exterior hoof wall and horn of the sole is made of keratin, the same material as a human fingernail. The result is that a horse, weighing on average 500 kilograms (1,100 lb), travels on the same bones as would a human on tiptoe. For the protection of the hoof under certain conditions, some horses have horseshoes placed on their feet by a professional farrier. The hoof continually grows, and in most domesticated horses needs to be trimmed (and horseshoes reset, if used) every five to eight weeks, though the hooves of horses in the wild wear down and regrow at a rate suitable for their terrain.

 

Teeth

Main article: Horse teeth

Horses are adapted to grazing. In an adult horse, there are 12 incisors at the front of the mouth, adapted to biting off the grass or other vegetation. There are 24 teeth adapted for chewing, the premolars and molars, at the back of the mouth. Stallions and geldings have four additional teeth just behind the incisors, a type of canine teeth called "tushes". Some horses, both male and female, will also develop one to four very small vestigial teeth in front of the molars, known as "wolf" teeth, which are generally removed because they can interfere with the bit. There is an empty interdental space between the incisors and the molars where the bit rests directly on the gums, or "bars" of the horse's mouth when the horse is bridled.

 

An estimate of a horse's age can be made from looking at its teeth. The teeth continue to erupt throughout life and are worn down by grazing. Therefore, the incisors show changes as the horse ages; they develop a distinct wear pattern, changes in tooth shape, and changes in the angle at which the chewing surfaces meet. This allows a very rough estimate of a horse's age, although diet and veterinary care can also affect the rate of tooth wear.

 

Digestion

Main articles: Equine digestive system and Equine nutrition

Horses are herbivores with a digestive system adapted to a forage diet of grasses and other plant material, consumed steadily throughout the day. Therefore, compared to humans, they have a relatively small stomach but very long intestines to facilitate a steady flow of nutrients. A 450-kilogram (990 lb) horse will eat 7 to 11 kilograms (15 to 24 lb) of food per day and, under normal use, drink 38 to 45 litres (8.4 to 9.9 imp gal; 10 to 12 US gal) of water. Horses are not ruminants, they have only one stomach, like humans, but unlike humans, they can digest cellulose, a major component of grass. Horses are hindgut fermenters. Cellulose fermentation by symbiotic bacteria occurs in the cecum, or "water gut", which food goes through before reaching the large intestine. Horses cannot vomit, so digestion problems can quickly cause colic, a leading cause of death. Horses do not have a gallbladder; however, they seem to tolerate high amounts of fat in their diet despite lack of a gallbladder.

 

Senses

The horses' senses are based on their status as prey animals, where they must be aware of their surroundings at all times. They have the largest eyes of any land mammal, and are lateral-eyed, meaning that their eyes are positioned on the sides of their heads. This means that horses have a range of vision of more than 350°, with approximately 65° of this being binocular vision and the remaining 285° monocular vision. Horses have excellent day and night vision, but they have two-color, or dichromatic vision; their color vision is somewhat like red-green color blindness in humans, where certain colors, especially red and related colors, appear as a shade of green.

 

Their sense of smell, while much better than that of humans, is not quite as good as that of a dog. It is believed to play a key role in the social interactions of horses as well as detecting other key scents in the environment. Horses have two olfactory centers. The first system is in the nostrils and nasal cavity, which analyze a wide range of odors. The second, located under the nasal cavity, are the vomeronasal organs, also called Jacobson's organs. These have a separate nerve pathway to the brain and appear to primarily analyze pheromones.

 

A horse's hearing is good, and the pinna of each ear can rotate up to 180°, giving the potential for 360° hearing without having to move the head. Noise impacts the behavior of horses and certain kinds of noise may contribute to stress: a 2013 study in the UK indicated that stabled horses were calmest in a quiet setting, or if listening to country or classical music, but displayed signs of nervousness when listening to jazz or rock music. This study also recommended keeping music under a volume of 21 decibels. An Australian study found that stabled racehorses listening to talk radio had a higher rate of gastric ulcers than horses listening to music, and racehorses stabled where a radio was played had a higher overall rate of ulceration than horses stabled where there was no radio playing.

 

Horses have a great sense of balance, due partly to their ability to feel their footing and partly to highly developed proprioception—the unconscious sense of where the body and limbs are at all times. A horse's sense of touch is well-developed. The most sensitive areas are around the eyes, ears, and nose. Horses are able to sense contact as subtle as an insect landing anywhere on the body.

 

Horses have an advanced sense of taste, which allows them to sort through fodder and choose what they would most like to eat, and their prehensile lips can easily sort even small grains. Horses generally will not eat poisonous plants, however, there are exceptions; horses will occasionally eat toxic amounts of poisonous plants even when there is adequate healthy food.

 

Movement

All horses move naturally with four basic gaits:

the four-beat walk, which averages 6.4 kilometres per hour (4.0 mph);

the two-beat trot or jog at 13 to 19 kilometres per hour (8.1 to 11.8 mph) (faster for harness racing horses);

the canter or lope, a three-beat gait that is 19 to 24 kilometres per hour (12 to 15 mph);

the gallop, which averages 40 to 48 kilometres per hour (25 to 30 mph), but the world record for a horse galloping over a short, sprint distance is 70.76 kilometres per hour (43.97 mph).

Besides these basic gaits, some horses perform a two-beat pace, instead of the trot. There also are several four-beat 'ambling' gaits that are approximately the speed of a trot or pace, though smoother to ride. These include the lateral rack, running walk, and tölt as well as the diagonal fox trot. Ambling gaits are often genetic in some breeds, known collectively as gaited horses. These horses replace the trot with one of the ambling gaits.

 

Behavior

Horses are prey animals with a strong fight-or-flight response. Their first reaction to a threat is to startle and usually flee, although they will stand their ground and defend themselves when flight is impossible or if their young are threatened. They also tend to be curious; when startled, they will often hesitate an instant to ascertain the cause of their fright, and may not always flee from something that they perceive as non-threatening. Most light horse riding breeds were developed for speed, agility, alertness and endurance; natural qualities that extend from their wild ancestors. However, through selective breeding, some breeds of horses are quite docile, particularly certain draft horses.

  

Horses fighting as part of herd dominance behaviour

Horses are herd animals, with a clear hierarchy of rank, led by a dominant individual, usually a mare. They are also social creatures that are able to form companionship attachments to their own species and to other animals, including humans. They communicate in various ways, including vocalizations such as nickering or whinnying, mutual grooming, and body language. Many horses will become difficult to manage if they are isolated, but with training, horses can learn to accept a human as a companion, and thus be comfortable away from other horses. However, when confined with insufficient companionship, exercise, or stimulation, individuals may develop stable vices, an assortment of bad habits, mostly stereotypies of psychological origin, that include wood chewing, wall kicking, "weaving" (rocking back and forth), and other problems.

 

Intelligence and learning

Studies have indicated that horses perform a number of cognitive tasks on a daily basis, meeting mental challenges that include food procurement and identification of individuals within a social system. They also have good spatial discrimination abilities. They are naturally curious and apt to investigate things they have not seen before. Studies have assessed equine intelligence in areas such as problem solving, speed of learning, and memory. Horses excel at simple learning, but also are able to use more advanced cognitive abilities that involve categorization and concept learning. They can learn using habituation, desensitization, classical conditioning, and operant conditioning, and positive and negative reinforcement. One study has indicated that horses can differentiate between "more or less" if the quantity involved is less than four.

 

Domesticated horses may face greater mental challenges than wild horses, because they live in artificial environments that prevent instinctive behavior whilst also learning tasks that are not natural. Horses are animals of habit that respond well to regimentation, and respond best when the same routines and techniques are used consistently. One trainer believes that "intelligent" horses are reflections of intelligent trainers who effectively use response conditioning techniques and positive reinforcement to train in the style that best fits with an individual animal's natural inclinations.

 

Temperament

Horses are mammals, and as such are warm-blooded, or endothermic creatures, as opposed to cold-blooded, or poikilothermic animals. However, these words have developed a separate meaning in the context of equine terminology, used to describe temperament, not body temperature. For example, the "hot-bloods", such as many race horses, exhibit more sensitivity and energy, while the "cold-bloods", such as most draft breeds, are quieter and calmer. Sometimes "hot-bloods" are classified as "light horses" or "riding horses", with the "cold-bloods" classified as "draft horses" or "work horses".

 

a sepia-toned engraving from an old book, showing 11 horses of different breeds and sizes in nine different illustrations

Illustration of assorted breeds; slim, light hotbloods, medium-sized warmbloods and draft and pony-type coldblood breeds

"Hot blooded" breeds include "oriental horses" such as the Akhal-Teke, Arabian horse, Barb, and now-extinct Turkoman horse, as well as the Thoroughbred, a breed developed in England from the older oriental breeds. Hot bloods tend to be spirited, bold, and learn quickly. They are bred for agility and speed. They tend to be physically refined—thin-skinned, slim, and long-legged. The original oriental breeds were brought to Europe from the Middle East and North Africa when European breeders wished to infuse these traits into racing and light cavalry horses.

 

Muscular, heavy draft horses are known as "cold bloods", as they are bred not only for strength, but also to have the calm, patient temperament needed to pull a plow or a heavy carriage full of people. They are sometimes nicknamed "gentle giants". Well-known draft breeds include the Belgian and the Clydesdale. Some, like the Percheron, are lighter and livelier, developed to pull carriages or to plow large fields in drier climates. Others, such as the Shire, are slower and more powerful, bred to plow fields with heavy, clay-based soils. The cold-blooded group also includes some pony breeds.

 

"Warmblood" breeds, such as the Trakehner or Hanoverian, developed when European carriage and war horses were crossed with Arabians or Thoroughbreds, producing a riding horse with more refinement than a draft horse, but greater size and milder temperament than a lighter breed. Certain pony breeds with warmblood characteristics have been developed for smaller riders. Warmbloods are considered a "light horse" or "riding horse".

 

Today, the term "Warmblood" refers to a specific subset of sport horse breeds that are used for competition in dressage and show jumping. Strictly speaking, the term "warm blood" refers to any cross between cold-blooded and hot-blooded breeds. Examples include breeds such as the Irish Draught or the Cleveland Bay. The term was once used to refer to breeds of light riding horse other than Thoroughbreds or Arabians, such as the Morgan horse.

 

Sleep patterns

When horses lie down to sleep, others in the herd remain standing, awake, or in a light doze, keeping watch.

Horses are able to sleep both standing up and lying down. In an adaptation from life in the wild, horses are able to enter light sleep by using a "stay apparatus" in their legs, allowing them to doze without collapsing. Horses sleep better when in groups because some animals will sleep while others stand guard to watch for predators. A horse kept alone will not sleep well because its instincts are to keep a constant eye out for danger.

 

Unlike humans, horses do not sleep in a solid, unbroken period of time, but take many short periods of rest. Horses spend four to fifteen hours a day in standing rest, and from a few minutes to several hours lying down. Total sleep time in a 24-hour period may range from several minutes to a couple of hours, mostly in short intervals of about 15 minutes each. The average sleep time of a domestic horse is said to be 2.9 hours per day.

 

Horses must lie down to reach REM sleep. They only have to lie down for an hour or two every few days to meet their minimum REM sleep requirements. However, if a horse is never allowed to lie down, after several days it will become sleep-deprived, and in rare cases may suddenly collapse as it involuntarily slips into REM sleep while still standing. This condition differs from narcolepsy, although horses may also suffer from that disorder.

 

Taxonomy and evolution

The horse adapted to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not. Horses and other equids are odd-toed ungulates of the order Perissodactyla, a group of mammals dominant during the Tertiary period. In the past, this order contained 14 families, but only three—Equidae (the horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)—have survived to the present day.

 

The earliest known member of the family Equidae was the Hyracotherium, which lived between 45 and 55 million years ago, during the Eocene period. It had 4 toes on each front foot, and 3 toes on each back foot. The extra toe on the front feet soon disappeared with the Mesohippus, which lived 32 to 37 million years ago. Over time, the extra side toes shrank in size until they vanished. All that remains of them in modern horses is a set of small vestigial bones on the leg below the knee, known informally as splint bones. Their legs also lengthened as their toes disappeared until they were a hooved animal capable of running at great speed. By about 5 million years ago, the modern Equus had evolved. Equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, then to grazing of tougher plains grasses. Thus proto-horses changed from leaf-eating forest-dwellers to grass-eating inhabitants of semi-arid regions worldwide, including the steppes of Eurasia and the Great Plains of North America.

 

By about 15,000 years ago, Equus ferus was a widespread holarctic species. Horse bones from this time period, the late Pleistocene, are found in Europe, Eurasia, Beringia, and North America. Yet between 10,000 and 7,600 years ago, the horse became extinct in North America. The reasons for this extinction are not fully known, but one theory notes that extinction in North America paralleled human arrival. Another theory points to climate change, noting that approximately 12,500 years ago, the grasses characteristic of a steppe ecosystem gave way to shrub tundra, which was covered with unpalatable plants.

 

Wild species surviving into modern times

Three tan-colored horses with upright manes. Two horses nip and paw at each other, while the third moves towards the camera. They stand in an open, rocky grassland, with forests in the distance.

 

Main article: Wild horse

A truly wild horse is a species or subspecies with no ancestors that were ever successfully domesticated. Therefore, most "wild" horses today are actually feral horses, animals that escaped or were turned loose from domestic herds and the descendants of those animals. Only two wild subspecies, the tarpan and the Przewalski's horse, survived into recorded history and only the latter survives today.

 

The Przewalski's horse (Equus ferus przewalskii), named after the Russian explorer Nikolai Przhevalsky, is a rare Asian animal. It is also known as the Mongolian wild horse; Mongolian people know it as the taki, and the Kyrgyz people call it a kirtag. The subspecies was presumed extinct in the wild between 1969 and 1992, while a small breeding population survived in zoos around the world. In 1992, it was reestablished in the wild by the conservation efforts of numerous zoos. Today, a small wild breeding population exists in Mongolia. There are additional animals still maintained at zoos throughout the world.

 

The question of whether the Przewalski's horse was ever domesticated was challenged in 2018 when DNA studies of horses found at Botai culture sites revealed captured animals with DNA markers of an ancestor to the Przewalski's horse. The study concluded that the Botai animals appear to have been an independent domestication attempt and apparently unsuccessful, as these genetic markers do not appear in modern domesticated horses. However, the question of whether all Przewalski's horses descend from this population is also unresolved, as only one of seven modern Przewalski's horses in the study shared this ancestry.

 

The tarpan or European wild horse (Equus ferus ferus) was found in Europe and much of Asia. It survived into the historical era, but became extinct in 1909, when the last captive died in a Russian zoo. Thus, the genetic line was lost. Attempts have been made to recreate the tarpan, which resulted in horses with outward physical similarities, but nonetheless descended from domesticated ancestors and not true wild horses.

 

Periodically, populations of horses in isolated areas are speculated to be relict populations of wild horses, but generally have been proven to be feral or domestic. For example, the Riwoche horse of Tibet was proposed as such, but testing did not reveal genetic differences from domesticated horses. Similarly, the Sorraia of Portugal was proposed as a direct descendant of the Tarpan on the basis of shared characteristics, but genetic studies have shown that the Sorraia is more closely related to other horse breeds, and that the outward similarity is an unreliable measure of relatedness.

 

Other modern equids

Main article: Equus (genus)

Besides the horse, there are six other species of genus Equus in the Equidae family. These are the ass or donkey, Equus asinus; the mountain zebra, Equus zebra; plains zebra, Equus quagga; Grévy's Zebra, Equus grevyi; the kiang, Equus kiang; and the onager, Equus hemionus.

 

Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a "jenny" (female donkey). Other hybrids include the zorse, a cross between a zebra and a horse. With rare exceptions, most hybrids are sterile and cannot reproduce.

 

Main articles: History of horse domestication theories and Domestication of the horse

Domestication of the horse most likely took place in central Asia prior to 3500 BCE. Two major sources of information are used to determine where and when the horse was first domesticated and how the domesticated horse spread around the world. The first source is based on palaeological and archaeological discoveries; the second source is a comparison of DNA obtained from modern horses to that from bones and teeth of ancient horse remains.

 

The earliest archaeological evidence for the domestication of the horse comes from sites in Ukraine and Kazakhstan, dating to approximately 4000–3500 BCE. By 3000 BCE, the horse was completely domesticated and by 2000 BCE there was a sharp increase in the number of horse bones found in human settlements in northwestern Europe, indicating the spread of domesticated horses throughout the continent. The most recent, but most irrefutable evidence of domestication comes from sites where horse remains were interred with chariots in graves of the Sintashta and Petrovka cultures c. 2100 BCE.

 

A 2021 genetic study suggested that most modern domestic horses descend from the lower Volga-Don region. Ancient horse genomes indicate that these populations influenced almost all local populations as they expanded rapidly throughout Eurasia, beginning about 4,200 years ago. It also shows that certain adaptations were strongly selected due to riding, and that equestrian material culture, including Sintashta spoke-wheeled chariots spread with the horse itself.

 

Domestication is also studied by using the genetic material of present-day horses and comparing it with the genetic material present in the bones and teeth of horse remains found in archaeological and palaeological excavations. The variation in the genetic material shows that very few wild stallions contributed to the domestic horse, while many mares were part of early domesticated herds. This is reflected in the difference in genetic variation between the DNA that is passed on along the paternal, or sire line (Y-chromosome) versus that passed on along the maternal, or dam line (mitochondrial DNA). There are very low levels of Y-chromosome variability, but a great deal of genetic variation in mitochondrial DNA. There is also regional variation in mitochondrial DNA due to the inclusion of wild mares in domestic herds. Another characteristic of domestication is an increase in coat color variation. In horses, this increased dramatically between 5000 and 3000 BCE.

 

Before the availability of DNA techniques to resolve the questions related to the domestication of the horse, various hypotheses were proposed. One classification was based on body types and conformation, suggesting the presence of four basic prototypes that had adapted to their environment prior to domestication. Another hypothesis held that the four prototypes originated from a single wild species and that all different body types were entirely a result of selective breeding after domestication. However, the lack of a detectable substructure in the horse has resulted in a rejection of both hypotheses.

 

Main article: Feral horse

Feral horses are born and live in the wild, but are descended from domesticated animals. Many populations of feral horses exist throughout the world. Studies of feral herds have provided useful insights into the behavior of prehistoric horses, as well as greater understanding of the instincts and behaviors that drive horses that live in domesticated conditions.

 

There are also semi-feral horses in many parts of the world, such as Dartmoor and the New Forest in the UK, where the animals are all privately owned but live for significant amounts of time in "wild" conditions on undeveloped, often public, lands. Owners of such animals often pay a fee for grazing rights.

 

Main articles: Horse breed, List of horse breeds, and Horse breeding

The concept of purebred bloodstock and a controlled, written breed registry has come to be particularly significant and important in modern times. Sometimes purebred horses are incorrectly or inaccurately called "thoroughbreds". Thoroughbred is a specific breed of horse, while a "purebred" is a horse (or any other animal) with a defined pedigree recognized by a breed registry. Horse breeds are groups of horses with distinctive characteristics that are transmitted consistently to their offspring, such as conformation, color, performance ability, or disposition. These inherited traits result from a combination of natural crosses and artificial selection methods. Horses have been selectively bred since their domestication. An early example of people who practiced selective horse breeding were the Bedouin, who had a reputation for careful practices, keeping extensive pedigrees of their Arabian horses and placing great value upon pure bloodlines. These pedigrees were originally transmitted via an oral tradition. In the 14th century, Carthusian monks of southern Spain kept meticulous pedigrees of bloodstock lineages still found today in the Andalusian horse.

 

Breeds developed due to a need for "form to function", the necessity to develop certain characteristics in order to perform a particular type of work. Thus, a powerful but refined breed such as the Andalusian developed as riding horses with an aptitude for dressage. Heavy draft horses were developed out of a need to perform demanding farm work and pull heavy wagons. Other horse breeds had been developed specifically for light agricultural work, carriage and road work, various sport disciplines, or simply as pets. Some breeds developed through centuries of crossing other breeds, while others descended from a single foundation sire, or other limited or restricted foundation bloodstock. One of the earliest formal registries was General Stud Book for Thoroughbreds, which began in 1791 and traced back to the foundation bloodstock for the breed. There are more than 300 horse breeds in the world today.

 

Interaction with humans

Worldwide, horses play a role within human cultures and have done so for millennia. Horses are used for leisure activities, sports, and working purposes. The Food and Agriculture Organization (FAO) estimates that in 2008, there were almost 59,000,000 horses in the world, with around 33,500,000 in the Americas, 13,800,000 in Asia and 6,300,000 in Europe and smaller portions in Africa and Oceania. There are estimated to be 9,500,000 horses in the United States alone. The American Horse Council estimates that horse-related activities have a direct impact on the economy of the United States of over $39 billion, and when indirect spending is considered, the impact is over $102 billion. In a 2004 "poll" conducted by Animal Planet, more than 50,000 viewers from 73 countries voted for the horse as the world's 4th favorite animal.

 

Communication between human and horse is paramount in any equestrian activity; to aid this process horses are usually ridden with a saddle on their backs to assist the rider with balance and positioning, and a bridle or related headgear to assist the rider in maintaining control. Sometimes horses are ridden without a saddle, and occasionally, horses are trained to perform without a bridle or other headgear. Many horses are also driven, which requires a harness, bridle, and some type of vehicle.

 

Main articles: Equestrianism, Horse racing, Horse training, and Horse tack

Historically, equestrians honed their skills through games and races. Equestrian sports provided entertainment for crowds and honed the excellent horsemanship that was needed in battle. Many sports, such as dressage, eventing, and show jumping, have origins in military training, which were focused on control and balance of both horse and rider. Other sports, such as rodeo, developed from practical skills such as those needed on working ranches and stations. Sport hunting from horseback evolved from earlier practical hunting techniques. Horse racing of all types evolved from impromptu competitions between riders or drivers. All forms of competition, requiring demanding and specialized skills from both horse and rider, resulted in the systematic development of specialized breeds and equipment for each sport. The popularity of equestrian sports through the centuries has resulted in the preservation of skills that would otherwise have disappeared after horses stopped being used in combat.

 

Horses are trained to be ridden or driven in a variety of sporting competitions. Examples include show jumping, dressage, three-day eventing, competitive driving, endurance riding, gymkhana, rodeos, and fox hunting. Horse shows, which have their origins in medieval European fairs, are held around the world. They host a huge range of classes, covering all of the mounted and harness disciplines, as well as "In-hand" classes where the horses are led, rather than ridden, to be evaluated on their conformation. The method of judging varies with the discipline, but winning usually depends on style and ability of both horse and rider. Sports such as polo do not judge the horse itself, but rather use the horse as a partner for human competitors as a necessary part of the game. Although the horse requires specialized training to participate, the details of its performance are not judged, only the result of the rider's actions—be it getting a ball through a goal or some other task. Examples of these sports of partnership between human and horse include jousting, in which the main goal is for one rider to unseat the other, and buzkashi, a team game played throughout Central Asia, the aim being to capture a goat carcass while on horseback.

 

Horse racing is an equestrian sport and major international industry, watched in almost every nation of the world. There are three types: "flat" racing; steeplechasing, i.e. racing over jumps; and harness racing, where horses trot or pace while pulling a driver in a small, light cart known as a sulky. A major part of horse racing's economic importance lies in the gambling associated with it.

 

Work

There are certain jobs that horses do very well, and no technology has yet developed to fully replace them. For example, mounted police horses are still effective for certain types of patrol duties and crowd control. Cattle ranches still require riders on horseback to round up cattle that are scattered across remote, rugged terrain. Search and rescue organizations in some countries depend upon mounted teams to locate people, particularly hikers and children, and to provide disaster relief assistance. Horses can also be used in areas where it is necessary to avoid vehicular disruption to delicate soil, such as nature reserves. They may also be the only form of transport allowed in wilderness areas. Horses are quieter than motorized vehicles. Law enforcement officers such as park rangers or game wardens may use horses for patrols, and horses or mules may also be used for clearing trails or other work in areas of rough terrain where vehicles are less effective.

 

Although machinery has replaced horses in many parts of the world, an estimated 100 million horses, donkeys and mules are still used for agriculture and transportation in less developed areas. This number includes around 27 million working animals in Africa alone. Some land management practices such as cultivating and logging can be efficiently performed with horses. In agriculture, less fossil fuel is used and increased environmental conservation occurs over time with the use of draft animals such as horses. Logging with horses can result in reduced damage to soil structure and less damage to trees due to more selective logging.

 

Main article: Horses in warfare

Horses have been used in warfare for most of recorded history. The first archaeological evidence of horses used in warfare dates to between 4000 and 3000 BCE, and the use of horses in warfare was widespread by the end of the Bronze Age. Although mechanization has largely replaced the horse as a weapon of war, horses are still seen today in limited military uses, mostly for ceremonial purposes, or for reconnaissance and transport activities in areas of rough terrain where motorized vehicles are ineffective. Horses have been used in the 21st century by the Janjaweed militias in the War in Darfur.

 

Entertainment and culture

Modern horses are often used to reenact many of their historical work purposes. Horses are used, complete with equipment that is authentic or a meticulously recreated replica, in various live action historical reenactments of specific periods of history, especially recreations of famous battles. Horses are also used to preserve cultural traditions and for ceremonial purposes. Countries such as the United Kingdom still use horse-drawn carriages to convey royalty and other VIPs to and from certain culturally significant events. Public exhibitions are another example, such as the Budweiser Clydesdales, seen in parades and other public settings, a team of draft horses that pull a beer wagon similar to that used before the invention of the modern motorized truck.

 

Horses are frequently used in television, films and literature. They are sometimes featured as a major character in films about particular animals, but also used as visual elements that assure the accuracy of historical stories. Both live horses and iconic images of horses are used in advertising to promote a variety of products. The horse frequently appears in coats of arms in heraldry, in a variety of poses and equipment. The mythologies of many cultures, including Greco-Roman, Hindu, Islamic, and Germanic, include references to both normal horses and those with wings or additional limbs, and multiple myths also call upon the horse to draw the chariots of the Moon and Sun. The horse also appears in the 12-year cycle of animals in the Chinese zodiac related to the Chinese calendar.

 

Horses serve as the inspiration for many modern automobile names and logos, including the Ford Pinto, Ford Bronco, Ford Mustang, Hyundai Equus, Hyundai Pony, Mitsubishi Starion, Subaru Brumby, Mitsubishi Colt/Dodge Colt, Pinzgauer, Steyr-Puch Haflinger, Pegaso, Porsche, Rolls-Royce Camargue, Ferrari, Carlsson, Kamaz, Corre La Licorne, Iran Khodro, Eicher, and Baojun. Indian TVS Motor Company also uses a horse on their motorcycles & scooters.

 

Therapeutic use

People of all ages with physical and mental disabilities obtain beneficial results from an association with horses. Therapeutic riding is used to mentally and physically stimulate disabled persons and help them improve their lives through improved balance and coordination, increased self-confidence, and a greater feeling of freedom and independence. The benefits of equestrian activity for people with disabilities has also been recognized with the addition of equestrian events to the Paralympic Games and recognition of para-equestrian events by the International Federation for Equestrian Sports (FEI). Hippotherapy and therapeutic horseback riding are names for different physical, occupational, and speech therapy treatment strategies that use equine movement. In hippotherapy, a therapist uses the horse's movement to improve their patient's cognitive, coordination, balance, and fine motor skills, whereas therapeutic horseback riding uses specific riding skills.

 

Horses also provide psychological benefits to people whether they actually ride or not. "Equine-assisted" or "equine-facilitated" therapy is a form of experiential psychotherapy that uses horses as companion animals to assist people with mental illness, including anxiety disorders, psychotic disorders, mood disorders, behavioral difficulties, and those who are going through major life changes. There are also experimental programs using horses in prison settings. Exposure to horses appears to improve the behavior of inmates and help reduce recidivism when they leave.

 

Products

Horses are raw material for many products made by humans throughout history, including byproducts from the slaughter of horses as well as materials collected from living horses.

 

Products collected from living horses include mare's milk, used by people with large horse herds, such as the Mongols, who let it ferment to produce kumis. Horse blood was once used as food by the Mongols and other nomadic tribes, who found it a convenient source of nutrition when traveling. Drinking their own horses' blood allowed the Mongols to ride for extended periods of time without stopping to eat. The drug Premarin is a mixture of estrogens extracted from the urine of pregnant mares (pregnant mares' urine), and was previously a widely used drug for hormone replacement therapy. The tail hair of horses can be used for making bows for string instruments such as the violin, viola, cello, and double bass.

 

Horse meat has been used as food for humans and carnivorous animals throughout the ages. Approximately 5 million horses are slaughtered each year for meat worldwide. It is eaten in many parts of the world, though consumption is taboo in some cultures, and a subject of political controversy in others. Horsehide leather has been used for boots, gloves, jackets, baseballs, and baseball gloves. Horse hooves can also be used to produce animal glue. Horse bones can be used to make implements. Specifically, in Italian cuisine, the horse tibia is sharpened into a probe called a spinto, which is used to test the readiness of a (pig) ham as it cures. In Asia, the saba is a horsehide vessel used in the production of kumis.

 

Main article: Horse care

Checking teeth and other physical examinations are an important part of horse care.

Horses are grazing animals, and their major source of nutrients is good-quality forage from hay or pasture. They can consume approximately 2% to 2.5% of their body weight in dry feed each day. Therefore, a 450-kilogram (990 lb) adult horse could eat up to 11 kilograms (24 lb) of food. Sometimes, concentrated feed such as grain is fed in addition to pasture or hay, especially when the animal is very active. When grain is fed, equine nutritionists recommend that 50% or more of the animal's diet by weight should still be forage.

 

Horses require a plentiful supply of clean water, a minimum of 38 to 45 litres (10 to 12 US gal) per day. Although horses are adapted to live outside, they require shelter from the wind and precipitation, which can range from a simple shed or shelter to an elaborate stable.

 

Horses require routine hoof care from a farrier, as well as vaccinations to protect against various diseases, and dental examinations from a veterinarian or a specialized equine dentist. If horses are kept inside in a barn, they require regular daily exercise for their physical health and mental well-being. When turned outside, they require well-maintained, sturdy fences to be safely contained. Regular grooming is also helpful to help the horse maintain good health of the hair coat and underlying skin.

 

Climate change

As of 2019, there are around 17 million horses in the world. Healthy body temperature for adult horses is in the range between 37.5 and 38.5 °C (99.5 and 101.3 °F), which they can maintain while ambient temperatures are between 5 and 25 °C (41 and 77 °F). However, strenuous exercise increases core body temperature by 1 °C (1.8 °F)/minute, as 80% of the energy used by equine muscles is released as heat. Along with bovines and primates, equines are the only animal group which use sweating as their primary method of thermoregulation: in fact, it can account for up to 70% of their heat loss, and horses sweat three times more than humans while undergoing comparably strenuous physical activity. Unlike humans, this sweat is created not by eccrine glands but by apocrine glands. In hot conditions, horses during three hours of moderate-intersity exercise can loss 30 to 35 L of water and 100g of sodium, 198 g of choloride and 45 g of potassium. In another difference from humans, their sweat is hypertonic, and contains a protein called latherin, which enables it to spread across their body easier, and to foam, rather than to drip off. These adaptations are partly to compensate for their lower body surface-to-mass ratio, which makes it more difficult for horses to passively radiate heat. Yet, prolonged exposure to very hot and/or humid conditions will lead to consequences such as anhidrosis, heat stroke, or brain damage, potentially culminating in death if not addressed with measures like cold water applications. Additionally, around 10% of incidents associated with horse transport have been attributed to heat stress. These issues are expected to worsen in the future.

 

African horse sickness (AHS) is a viral illness with a mortality close to 90% in horses, and 50% in mules. A midge, Culicoides imicola, is the primary vector of AHS, and its spread is expected to benefit from climate change. The spillover of Hendra virus from its flying fox hosts to horses is also likely to increase, as future warming would expand the hosts' geographic range. It has been estimated that under the "moderate" and high climate change scenarios, RCP4.5 and RCP8.5, the number of threatened horses would increase by 110,000 and 165,000, respectively, or by 175 and 260%

Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.

 

The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.

 

The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.

 

Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.

 

There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.

 

Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.

 

Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.

 

Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.

 

Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.

 

Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.

 

All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.

 

Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.

 

After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.

 

Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.

 

Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).

 

Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.

 

Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.

 

Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.

 

Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).

 

Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.

 

So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).

 

Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.

 

The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.

 

Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.

 

In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.

 

Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.

 

Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.

 

Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.

 

The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.

 

The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.

 

The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.

 

The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.

 

The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.

 

Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.

 

Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.

 

Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.

 

The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.

 

The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.

 

Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.

 

Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.

 

Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.

 

The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.

 

Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.

 

Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.

 

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.

 

The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.

 

The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.

 

The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.

 

The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).

 

The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.

 

Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.

 

There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.

 

Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.

 

Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.

 

As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.

 

The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).

 

The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.

 

Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.

 

Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.

 

Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.

 

Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.

 

A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.

 

An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.

  

This is not a Police Reward Poster!

On the left : the daughter, not yet married, so no lip plate , just ear wooden ring, on the right: mother, married, with a big labret. Mursi tribe, southe Ethiopia. Few tribes in the world still wear lip plate.

Mursi woman with her giant lip plate, a sign of beauty in Mursi tribe, like in Surma one. When they are ready to marry, they start to make a hole in the lip with a wood stick.

It will be kept for one night , and is removed to put a bigger one. This is very painful at this time... Few months after, the lip plate has its full size, and the girl is seen as beautiful by the men.

The lip plate made of wood or terracotta, and they have to remove the lower incisors to let some space for the disc. it's amazing to see them speak without any trouble, put it and remove it as a classic jewel.

Sometimes the lip is broken by the pressure of the lip plate. This is a very big problem for the girl cos men will consider her as ugly, she won't be able to marry anyone in the tribe apart the old men or the sick people...

The women are shaved, like the men, cos they hate hairiness!

 

© Eric Lafforgue

www.ericlafforgue.com

More stories at: antoinegady.tumblr.com

 

Manatees (family Trichechidae, genus Trichechus) are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species in the order Sirenia: the Amazonian manatee (Trichechus inunguis), the West Indian manatee (Trichechus manatus), and the West African manatee (Trichechus senegalensis). They measure up to 13 feet (4.0 m) long, weigh as much as 1,300 pounds (590 kg),[1] and have paddle-like flippers. The name manatí comes from the Taíno, a pre-Columbian people of the Caribbean, meaning "breast".

Manatees have a mass of 400 to 550 kilograms (880 to 1,210 lb), and mean length of 2.8 to 3.0 metres (9.2 to 9.8 ft), with maxima of 3.6 metres (12 ft) and 1,775 kilograms (3,913 lb) seen (the females tend to be larger and heavier). When born, baby manatees have an average mass of 30 kilograms (66 lb). They have a large, flexible, prehensile upper lip. They use the lip to gather food and eat, as well as using it for social interactions and communications. Manatees have shorter snouts than their fellow sirenians, the dugongs. Their small, widely-spaced eyes have eyelids that close in a circular manner. The adults have no incisor or canine teeth, just a set of cheek teeth, which are not clearly differentiated into molars and premolars. These teeth are continuously replaced throughout life, with new teeth growing at the rear as older teeth fall out from farther forward in the mouth. This process is known as polyphydonty and amongst the other mammals, only occurs in the kangaroo[4] and elephant.[5][6] At any given time, a manatee typically has no more than six teeth in each jaw of its mouth.[7] Its tail is paddle-shaped, and is the clearest visible difference between manatees and dugongs; a dugong tail is fluked, similar in shape to a that of a whale. Females have two teats, one under each flipper,[8] a characteristic that was used to make early links between the manatee and elephants.

Manatees are unusual amongst mammals in possessing just six cervical vertebrae,[9] which may be due to mutations in the homeotic genes.[10] All other mammals have seven cervical vertebrae,[11] other than the two-toed and three-toed sloths.

Like horses, they have a simple stomach, but a large cecum, in which they can digest tough plant matter. In general, their intestines have a typical length of about 45 meters, which is unusually long for animals of their size.[12] Manatees produce enormous amounts of gas, which contributes to their barrel-shape, to aid in the digestion of their food.[13]

Manatees are the only animal known to have a vascularized cornea.

Swimming

On average, manatees swim at about 5 to 8 kilometres per hour (3 to 5 mph). However, they have been known to swim at up to 30 kilometres per hour (20 mph) in short bursts.

Intelligence

Manatees are capable of understanding discrimination tasks, and show signs of complex associated learning and advanced long term memory.[15] They demonstrate complex discrimination and task-learning similar to dolphins and pinnipeds in acoustic and visual studies.

From Wikipedia "Manatee"

This incredible image of a Gelada was taken by ORYX CEO Marius Coetzee on a photographic tour to one of his most favorite destinations, Ethiopia.

 

The Gelada, sometimes called the Gelada baboon and Bleeding-heart baboon, is a species of Old World monkey found only in the Ethiopian Highlands, with very large populations in the Semien Mountains. Their relaxed behavior around people make them a favorite amongst wildlife photographers. Geladas have several adaptations for their terrestrial and graminivorous (grass-eating) lifestyle. They have small, sturdy fingers adapted for pulling grass and narrow, small incisors adapted for chewing it. They live at altitudes ranging from 1800-4400 meters above sea level.For more info about tours in Ethopia you are welcome to visit www.oryxphotography.com

#wildlifephotography #Ethiopia #wildlifesafari

9 x 12

 

© Brian E Kushner

 

Was out back shooting the Southern Flying Squirrels and this guy/gal wondered up next to where I was standing. Took a few seconds before it realized I was standing there and it took off. I get a lot of animals in the back but don't see the possums too often.

 

Didelphimoarphi (pronounced /daɪˌdɛlfɨˈmɔrfi.ə/) is the order of common opossums of the Western Hemisphere. They are commonly also called possums, though that term is also applied to Australian fauna of the suborder Phalangeriformes. The Virginia Opossum is the original animal named opossum. The word comes from Algonquian wapathemwa. Opossums probably diverged from the basic South American marsupials in the late Cretaceous or early Paleocene. A sister group is Paucituberculata (shrew opossums).

 

Their unspecialized biology, flexible diet and reproductive strategy make them successful colonizers and survivors in diverse locations and conditions. Originally native to the eastern United States, the Virginia Opossum was intentionally introduced into the West during the Great Depression, probably as a source of food.[2] Its range has been expanding steadily northwards, thanks in part to more plentiful, man-made sources of freshwater, increased shelter due to urban encroachment, and milder winters. Its range has extended into Ontario, Canada, and it has been found farther north than Toronto.

 

Characteristics

 

Didelphimorphs are small to medium-sized marsupials, with the largest about the size of a large house cat, and the smallest the size of a mouse. They tend to be semi-arboreal omnivores, although there are many exceptions. Most members of this taxon have long snouts, a narrow braincase, and a prominent sagittal crest. The dental formula is:

Dentition

5.1.3.4

4.1.3.4

 

By mammalian standards, this is a very full jaw. Opossums have more teeth than any other land mammal; only aquatic mammals have more.[citation needed] The incisors are very small, the canines large, and the molars are tricuspid.

 

Didelphimorphs have a plantigrade stance (feet flat on the ground) and the hind feet have an opposable digit with no claw. Like some New World monkeys, opossums have prehensile tails. The stomach is simple, with a small cecum.

 

Opossums have a remarkably robust immune system, and show partial or total immunity to the venom of rattlesnakes, cottonmouths, and other pit vipers.[3][4] Opossums are about eight times less likely to carry rabies than wild dogs, and about one in eight hundred opossums are infected with this virus.[5]

 

[edit] Reproduction and life cycle

Sleeping Virginia opossum with babies in her relaxed pouch

 

As a marsupial, the opossum has a reproductive system that is composed of a placenta and a marsupium, which is the pouch.[6] The young are born at a very early stage, although the gestation period is similar to many other small marsupials, at only 12 to 14 days.[7] Once born, the offspring must find their way into the marsupium to hold onto and nurse from a teat. The species are moderately sexually dimorphic with males usually being slightly larger, much heavier, and having larger canines than females.[8] The largest difference between the opossum and other mammals is the bifurcated penis of the male and bifurcated vagina of the female (the source of the Latin didelphis, meaning double-wombed). Male opossum spermatozoa exhibit cooperative methods of ensuring the survival of genotypically similar sperm by forming conjugate pairs before fertilization[9] . Such measures come into place particularly when females copulate with multiple males. These conjugate pairs increase motility and enhance the likelihood of fertilization. Conjugate pairs dissociate into separate spermatozoa before fertilization. The opossum is one of many species that employs sperm cooperation in its reproductive life cycle.

 

Female opossums often give birth to very large numbers of young, most of which fail to attach to a teat, although as many as thirteen young can attach[8], and therefore survive, depending on species. The young are weaned between 70 and 125 days, when they detach from the teat and leave the pouch. The opossum lifespan is unusually short for a mammal of its size, usually only two to four years. Senescence is rapid.[10]

 

[edit] Diet

 

Didelphimorphs are opportunistic omnivores with a very broad diet. Their diet mainly consists of carrion and many individual opossums are killed on the highway when scavenging for roadkill. They are also known to eat insects, frogs, birds, snakes, small mammals, and earthworms. Some of their favorite foods are fruits, and they are known to eat apples and persimmons. Their broad diet allows them to take advantage of many sources of food provided by human habitation such as unsecured food waste (garbage) and pet food.

Opossum fur is quite soft.

 

[edit] Behavior

 

Opossums are usually solitary and nomadic, staying in one area as long as food and water are easily available. Some families will group together in ready-made burrows or even under houses. Though they will temporarily occupy abandoned burrows, they do not dig or put much effort into building their own. As nocturnal animals, they favor dark, secure areas. These areas may be below ground or above.

Didelphis marsupialis: intrusion in human dwelling (French Guiana)

 

When threatened or harmed, they will play possum, mimicking the appearance and smell of a sick or dead animal. The lips are drawn back, teeth are bared, saliva foams around the mouth, and a foul-smelling fluid is secreted from the anal glands. The physiological response is involuntary, rather than a conscious act. Their stiff, curled form can be prodded, turned over, and even carried away. The animal will regain consciousness after a period of minutes or hours and escape.

 

Adult opossums do not hang from trees by their tails, though babies may dangle temporarily. Their semi-prehensile tails are not strong enough to support a mature adult's weight. Instead, the opossum uses its tail as a brace and a fifth limb when climbing. The tail is occasionally used as a grip to carry bunches of leaves or bedding materials to the nest. A mother will sometimes carry her young upon her back, where they will cling tightly even when she is climbing or running.

 

Threatened opossums (especially males) will growl deeply, raising their pitch as the threat becomes more urgent. Males make a clicking & smack; noise out of the side of their mouths as they wander in search of a mate, and females will sometimes repeat the sound in return. When separated or distressed, baby opossums will make a sneezing noise to signal their mother. If threatened, the baby will open its mouth and quietly hiss until the threat is gone.

The Virginia opposum is the only North American marsupial.

 

Historical references

 

An early description of the opossum comes from explorer John Smith, who wrote in Map of Virginia, with a Description of the Countrey, the Commodities, People, Government and Religion in 1608 that An Opassom hath an head like a Swine, and a taile like a Rat, and is of the bignes of a Cat. Under her belly she hath a bagge, wherein she lodgeth, carrieth, and sucketh her young.[11][12]. The Opossum was more formally described in 1698 in a published letter entitled Carigueya, Seu Marsupiale Americanum Masculum. Or, The Anatomy of a Male Opossum: In a Letter to Dr Edward Tyson, from Mr William Cowper, Chirurgeon, and Fellow of the Royal Society, London, by Edward Tyson, M. D. Fellow of the College of Physicians and of the Royal Society. The letter suggests even earlier descriptions.[13]

 

[edit] Hunting, food and foodways

 

The opossum was once a favorite game animal in the United States, and in particular the southern regions which have a large body of recipes and folklore relating to the opossum. Opossum was once widely consumed in the United States where available, as evidenced by recipes available online[14] and in books such as older editions of The Joy of Cooking. A traditional method of preparation is baking, sometimes in a pie or pasty[1], though at present possum pie & most often refers to a sweet confection containing no meat of any kind. In Dominica and Trinidad opossum or manicou is popular and can only be hunted during certain times of the year owing to over hunting; the meat is traditionally prepared by smoking then stewing. The meat is light and fine-grained, but the musk glands must be removed as part of preparation. The meat can be used in place of rabbit and chicken in recipes. The cousin of the opossum, the possum, found in Australia (and introduced to New Zealand ) is consumed in a similar manner. [15]

 

Historically, hunters in the Caribbean would place a barrel with fresh or rotten fruit to attract opossums who would feed on the fruit or insects. Cubans growing up in the mid-twentieth century tell of brushing the maggots out of the mouths of manicou caught in this manner to prepare them for consumption. It is said also that the gaminess of the meat causes gas.[citation needed]

 

In Mexico, opossums are known as tlacuache or &tlaquatzin. Their tails are eaten as a folk remedy to improve fertility.

 

Opossum oil (Possum grease) is high in essential fatty acids and has been used as a chest rub and a carrier for arthritis remedies given as topical salves.

Commentary.

 

Amazing Suilven changes in form

as we circumnavigate it.

From the west, a sugar-loaf dome, near vertical.

From others, a giant elephant.

West peak, its rump.

Central col, a dip in its backbone.

Easterly peak, a sharper point to the top of its skull.

From yet others it appears like an incisor tooth,

thrusting up from an undulating, rocky base

of “Knock and Lochan” or small hill and lake.

The mountains of Sutherland don’t reach 1,000 metres.

But because of their stark, isolated rise,

they seem double their actual height.

They arrest one’s attention.

They demand focus.

They bemuse, by constantly changing form, shape and character,

and none more so, than the captivating,

iconic, monolith known as Suilven!

 

These adorable creatures are rock hyraxes and we saw them around Betty's bay, in Tsitsikamma National Park and in lots of other places.

I like the Afrikaanse / Dutch name much better: klipdassies, more or less to be translated to rock badgers.

 

These are almost elephants!

The closest living relatives to hyraxes are the modern day elephants. The rock hyrax has a prominent pair of long, pointed tusk-like upper incisors which are reminiscent of the elephant. Also the feet have similarities, although I can't see that.

 

The rock hyrax is found across Africa, in habitats with rock crevices in which to escape from predators. Hyraxes typically live in groups of 10–80 animals, and forage as a group. Their most striking behaviour is the use of sentries: one or more animals take up position on a vantage point and issue alarm calls on the approach of predators.

BIG 5. Elephant. Hluhluwe–Imfolozi Park. South Africa. Dec/2019

 

Elephant

Elephants are large mammals of the family Elephantidae and the order Proboscidea. Three species are currently recognised: the African bush elephant (Loxodonta africana), the African forest elephant (L. cyclotis), and the Asian elephant (Elephas maximus). Elephants are scattered throughout sub-Saharan Africa, South Asia, and Southeast Asia. Elephantidae is the only surviving family of the order Proboscidea; other, now extinct, members of the order include deinotheres, gomphotheres, mammoths, and mastodons.

All elephants have several distinctive features, the most notable of which is a long trunk (also called a proboscis), used for many purposes, particularly breathing, lifting water, and grasping objects. Their incisors grow into tusks, which can serve as weapons and as tools for moving objects and digging. Elephants' large ear flaps help to control their body temperature. Their pillar-like legs can carry their great weight. African elephants have larger ears and concave backs while Asian elephants have smaller ears and convex or level backs.

Elephants are herbivorous and can be found in different habitats including savannahs, forests, deserts, and marshes. They prefer to stay near water. They are considered to be a keystone species due to their impact on their environments. Other animals tend to keep their distance from elephants while predators, such as lions, tigers, hyenas, and any wild dogs, usually target only young elephants (or "calves"). Elephants have a fission–fusion society in which multiple family groups come together to socialise. Females ("cows") tend to live in family groups, which can consist of one female with her calves or several related females with offspring. The groups are led by an individual known as the matriarch, often the oldest cow.

Males ("bulls") leave their family groups when they reach puberty and may live alone or with other males. Adult bulls mostly interact with family groups when looking for a mate and enter a state of increased testosterone and aggression known as musth, which helps them gain dominance and reproductive success. Calves are the centre of attention in their family groups and rely on their mothers for as long as three years. Elephants can live up to 70 years in the wild. They communicate by touch, sight, smell, and sound; elephants use infrasound, and seismic communication over long distances. Elephant intelligence has been compared with that of primates and cetaceans. They appear to have self-awareness and show empathyfor dying or dead individuals of their kind.

Source: Wikipedia

Elefante

Os elefantes são animais herbívoros, alimentando-se de ervas, gramíneas, frutas e folhas de árvores. Dado o seu tamanho, um elefante adulto pode ingerir entre 70 a 150 kg de alimentos por dia. As fêmeas vivem em manadas de 10 a 15 animais, lideradas por uma matriarca, compostas por várias reprodutoras e crias de variadas idades. O período de gestação das fêmeas é longo (20 a 22 meses), assim como o desenvolvimento do animal que leva anos a atingir a idade adulta. Os filhotes podem nascer com 90 kg. Os machos adolescentes tendem a viver em pequenos bandos e os machos adultos isolados, encontrando-se com as fêmeas apenas no período reprodutivo.

Devido ao seu porte, os elefantes têm poucos predadores. Exercem uma forte influência sobre as savanas, pois mantêm árvores e arbustos sob controle, permitindo que pastagens dominem o ambiente. Eles vivem cerca de 60 anos e morrem quando seus molares caem, impedindo que se alimentem de plantas.

Os elefantes-africanos são maiores que as variedades asiáticas e têm orelhas mais desenvolvidas, uma adaptação que permite libertar calor em condições de altas temperaturas. Outra diferença importante é a ausência de presas de marfim nas fêmeas dos elefantes asiáticos.

Durante a época de acasalamento, o aumento da produção de testosterona deixa os elefantes extremamente agressivos, fazendo-os atacar até humanos. Acidentes com elefantes utilizados em rituais geralmente são causados por esse motivo. Cerca de 400 humanos são mortos por elefantes a cada ano.

Elefante é o termo genérico e popular pelo qual são denominados os membros da família Elephantidae, um grupo de mamíferos proboscídeoselefantídeos, de grande porte, do qual há três espécies no mundo atual, duas africanas (Loxodonta sp.) e uma asiática (Elephas sp.). Há ainda os mamutes (Mammuthus sp.), hoje extintos. Até recentemente, acreditava-se que havia apenas duas espécies vivas de elefantes, o elefante-africano e o elefante-asiático, uma espécie menor. Entretanto, estudos recentes de DNA sugerem que havia, na verdade, duas espécies de elefante-africano: Loxodonta africana, da savana, e Loxodonta cyclotis, que vive nas florestas. Os elefantes são os maiores animais terrestres da actualidade, com a massa entre 4 a 6 toneladas e medindo em média quatro metros de altura, podem levantar até 10.000 kg. As suas características mais distintivas são as presas de marfim

Fonte: Wikipedia

  

Hluhluwe–Imfolozi Park

Hluhluwe–Imfolozi Park, formerly Hluhluwe–Umfolozi Game Reserve, is the oldest proclaimed nature reserve in Africa. It consists of 960 km² (96,000 ha) of hilly topography 280 kilometres (170 mi) north of Durban in central KwaZulu-Natal, South Africa and is known for its rich wildlife and conservation efforts. The park is the only state-run park in KwaZulu-Natal where each of the big five game animals can be found

Due to conservation efforts, the park in 2008 had the largest population of white rhino in the world

 

Umfolozi

This area is situated between the two Umfolozi Rivers where they divide into the Mfolozi emnyama ('Black Umfolozi') to the north and the Mfolozi emhlophe ('White Umfolozi') to the south. This area is to the south of the park and is generally hot in summer, and mild to cool in winter, although cold spells do occur. The topography in the Umfolozi section ranges from the lowlands of the Umfolozi River beds to steep hilly country, which includes some wide and deep valleys. Habitats in this area are primarily grasslands, which extend into acacia savannah and woodlands.

Hluhluwe

The Hluhluwe region has hilly topography where altitudes range from 80 to 540 metres (260 to 1,770 ft) above sea level. The high ridges support coastal scarp forests in a well-watered region with valley bushveld at lower levels. The north of the park is more rugged and mountainous with forests and grasslands and is known as the Hluhluwe area,[3] while the Umfolozi area is found to the south near the Black and White Umfolozi rivers where there is open savannah.

Source: Wikipedia

Parque Hluhluwe–Imfolozi

O Parque Hluhluwe – Imfolozi, anteriormente Reserva de Caça Hluhluwe – Umfolozi, é a mais antiga reserva natural proclamada da África. Consiste em 960 km² (96.000 ha) de topografia montanhosa a 280 quilômetros (170 milhas) ao norte de Durban, no centro de KwaZulu-Natal, África do Sul e é conhecida por seus ricos esforços de vida selvagem e conservação. O parque é o único parque estatal em KwaZulu-Natal, onde cada um dos cinco grandes animais de caça pode ser encontrado.

Devido aos esforços de conservação, o parque em 2008 teve a maior população de rinocerontes brancos do mundo

Umfolozi

Essa área está situada entre os dois rios Umfolozi, onde se dividem no Mfolozi emnyama ('Black Umfolozi') ao norte e o Mfolozi emhlophe ('White Umfolozi') ao sul. Essa área fica ao sul do parque e geralmente é quente no verão, e temperatura amena no inverno, embora ocorram períodos de frio. A topografia na seção de Umfolozi varia desde as planícies do leito do rio Umfolozi até a região montanhosa íngreme, que inclui alguns vales largos e profundos. Os habitats nesta área são principalmente pradarias, que se estendem até a savana de acácias e bosques.

Hluhluwe

A região de Hluhluwe possui topografia montanhosa, onde as altitudes variam de 80 a 540 metros (260 a 1.770 pés) acima do nível do mar. As altas cordilheiras sustentam florestas costeiras escarpadas em uma região bem regada, com vales em níveis mais baixos. O norte do parque é mais acidentado e montanhoso, com florestas e campos e é conhecido como a área de Hluhluwe, enquanto a área de Umfolozi fica ao sul, perto dos rios Umfolozi, onde há savanas abertas.

Fonte: Wikipedia (tradução livre)

 

view photo On black and large

while wire-walking across niagara i fell to thinking

 

you know how

if you make yourself some dhal

your teeth will find the one piece of grit

left in those otherwise purified pulses

 

or

 

those same investigative incisors

trap the only piece of gristle

in a steak

as tender as a lover’s thigh

 

that’s because deep down you look for it

 

i guess that’s why reality doesn’t get in the way

in a poem

i can tell how i watched a blackbird this morning

that gleam in his eye

as he pulled a worm

glistening into the sunlight

 

maybe i never left the house

stayed inside while the storm rattled the tiles

i see what i want to see

 

landscapes loves and memories

glide dance and change places

or

take me where i’ve never been

and

laugh with each other on the way back

 

feelings

fantasies

facts

 

i stir the phantom lentils

but

leave a little grit

 

………………………………………..

    

This animal lives at Colchester Zoo in Essex.

 

The binturong, also known as the bearcat is native to South and Southeast Asia.

The binturong is long and heavy, with short, stout legs. It has a thick coat of coarse black hair. The bushy and prehensile tail is thick at the root, gradually tapering, and curls inwards at the tip. The tail is nearly as long as the head and body, which ranges from 28 to 33 in. (71 to 84 cm), the tail is 26 to 27 in. (66 to 69 cm) long. The muzzle is short and pointed, somewhat turned up at the nose, and is covered with bristly hairs, brown at the points, which lengthen as they diverge, and form a peculiar radiated circle round the face. The eyes are large, black and prominent. The ears are short, rounded, edged with white, and terminated by tufts of black hair. There are six short rounded incisors in each jaw, two canines, which are long and sharp, and six molars on each side. The hair on the legs is short and of a yellowish tinge. The feet are five-toed, with large strong claws, the soles are padded and bare. The average weight of male binturong's is 29 lb. (13.3 kg) with females weighing 23 lb. (10.5 kg).

Binturong's are confined to tall rainforest and occurs from India, Nepal, Bangladesh, Bhutan, Myanmar, Thailand, Malaysia to Laos, Cambodia, Vietnam, Yunnan in China, Sumatra, Kalimantan and Java in Indonesia and Palawan in the Philippines.

The binturong is essentially arboreal (tree living) and hey tend to live in the canopy of tropical forests. When sleeping they lie curled up with their strong tail wrapped around a branch. They seldom leaped, but climbed skilfully, albeit slowly, progressing with equal ease and confidence along the upper side of branches or, upside down, beneath them. They are mostly nocturnal but are seen during the day.

The binturong is omnivorous, feeding on small mammals, birds, insects, rodents, eggs and fruits. If available it will eat fish and earthworms. Figs are a major component of its diet.

Binturongs are usually solitary in the wild, coming together only to mate. Binturongs usually give birth to two babies, called binlets, at a time. They are born with their eyes closed, and they cling to their mother’s fur for the first few days of their lives. They stay with their mother until they are independent, usually around 6 to 8 weeks old and sometimes even longer.

Other than humans, binturongs have no known predators and in the wild, binturongs live about 16 to 18 years. In captivity they can live to be 25 years old.

Major threats to the binturong are habitat loss due to logging and conversion of forests to non-forest land-uses throughout the binturong's range. In the Philippines, it is captured for the wildlife trade, In parts of Laos, it is considered a delicacy and also traded as a food item to Vietnam. In Laos, it is one of the most frequently displayed caged live carnivores and skins are frequently traded. It is uncommon in much of its range, and has been assessed as 'Vulnerable' on the IUCN Red List because of a declining population, that is estimated to have declined at least 30% since the mid-1980's.

 

The Pokhot live in the Baringo and Western Pokot districts of Kenya and in Uganda.

There are two main sub-groups depending of their location and way of life. The first group consist of the Hill Pokot who live in the rainy highlands in the west and in the central south, and are mainly farmers and pastoralists. The second group is made up of the Plains Pokot who live in dry and infertile plains, with their cattles. A homestead is composed of one or more buildings for a man, his wife and children; eventual co-wives live in separate houses. The role of the community in teaching children ethical rules. Most of the Pokot are nomadic and thus have interacted with different peoples, incorporating their social customs.The Pokot are very proud of their culture. The Songs, storytelling, and decorative arts, especially bodily decoration, are very appreciated. They adorn the body with beads, hairstyling, scarification, and the removal of the lower central incisors. Pokot girls wear a beaded necklace made of the stems of an asparagus tree. Most Pokot have some knowledge of herbal medicine, so they often use these treatments along with those of the hospitals. They belong to the Kenya's Nilotic-speaking peoples. .

For the Pokot, the universe has two realms: the above is the realm of the most powerful deities—Tororot, Asis (sun), and llat (rain); and the below is the one where live humans, animals, and plants. Humans are responsible for the realm that they inhabit, but they rely upon divinities to achieve and maintain peace and prosperity. They worship many deities like the sun, moon and believe in the spirit of death.The Pokot communicate with their deities through prayer and sacrifice. They perform it during ethnic festivals and dances. Oracles are responsible for maintaining the spiritual balance within the community. They are superstitious and believe in sorcery, so sometimes they call on shielding lucky sorcery. They have prophets, either male or female, who foresee advise, usually by the means of animal sacrifices. His or her ability is considered as a divine gift. Clan histories recount the changes of location, through poetry and song, emphasizing the vulnerability of humans and the importance of supernatural powers to help them overcome hunger, thirst, and even death. Ceremonies mark the transitions in the people's social lives. Among these are: the cleansing of a couple expecting their first child; the cleansing of newborn infants and their mothers; the cleansing of twins and other children who are born under unusual circumstances; male and female initiation; marriage; sapana, a coming-of-age ceremony for men; and summer-solstice, harvest, and healing ceremonies. The most important rite of passage for most Pokot is circumcision for boys and clitoridectomy for girls. These rites consist of a series of neighborhood-based ceremonies, emphasizing the importance of having a good behavior. When boys are circumcised, they acquire membership in one of eight age sets. Women do not have age-sets. After excisions, for several months, girls have a white painting on their face and wear a hood made of blackened leather with charcoal and oil. This means they are untouchable until the lepan ceremony, that marks the passage to womanhood. Unlike other tribes, the Pokot keep the affiliation to their clan throughout their lives, there is no disruption with marriage. Surprisingly, the agreement before marriage is made by gift giving, from the groom and his family to the bride and her family, often over a period of years (and not the contrary). It often implies the gift of a combination of livestock, goods, and cash to the bride's family, and the allotment of milk cows and rights to land to the bride. The bond between a husband and wife lasts for 3 generations, after what marriages can take place again between the two groups. Polygamy exists but is not prevalent among men before 40. The spirits of the elder anticipate reincarnation in their living descendants: when a child is said to resemble the elder, the same name is given. Disputes are resolved in neighborhood councils and in government courts. Some of the sanctions include shaming, cursing, and bewitching.

 

© Eric Lafforgue

www.ericlafforgue.com

 

Giovanni Battista Piranesi

Giovanni Battista Piranesi detto anche Giambattista (Mogliano Veneto, 4 ottobre 1720 – Roma, 9 novembre 1778) è stato un incisore, architetto e teorico dell'architettura italiano.

 

Le sue tavole incise, segnate da un'intonazione drammatica, appaiono improntate ad un'idea di dignità e magnificenza tutta romana, espressa attraverso la grandiosità e l'isolamento degli elementi architettonici, in modo da pervenire ad un sublime sentimento di grandezza del passato antico

Formazione

Giovanni Battista Piranesi nacque a Mogliano Veneto il 4 ottobre 1720 da Angelo e da Laura Lucchesi, e fu battezzato l'8 ottobre nella parrocchia di San Moisè. Venne introdotto allo studio dell'architettura dal padre, esperto tagliapietre e capomastro, e dallo zio materno Matteo Lucchesi, magistrato delle acque della Serenissima e amante dell'antico sui modelli di Andrea Palladio e di Vitruvio; dal colto fratello Angelo, frate domenicano, trasse invece una certa padronanza della lingua latina e il duraturo amore per Tito Livio e la storia di Roma. Dopo una controversia con lo zio, il giovane Giovanni Battista continuò la propria formazione con Giovanni Antonio Scalfarotto, anch'egli architetto orientato verso un gusto che già preannuncia il neoclassicismo; frequentò, inoltre, la bottega di Carlo Zucchi.

 

Nel 1740 Piranesi, divenuto consapevole delle scarse possibilità lavorative che gli avrebbe offerto il capoluogo veneto, decise di lasciare la propria terra patria e di trasferirsi a Roma, partecipando in qualità di disegnatore alla spedizione diplomatica del nuovo ambasciatore della Serenissima Francesco Venier. Partito il 9 settembre, arrivò nell'Urbe entro il mese, all'età di soli venti anni, ottenendo un alloggio presso palazzo Venezia. Rivelando ben presto le proprie attitudini da disegnatore, dopo l'iniziale apprendistato con i pittori-scenografi Domenico e Giuseppe Valeriani e con Giovanni Battista Nolli, intorno al 1742 il Piranesi apprese i rudimenti dell'acquaforte sotto la guida di Giuseppe Vasi, titolare di una bottega calcografica che al tempo godeva a Roma di una certa popolarità. Sempre nell'Urbe, inoltre, Piranesi ebbe modo di stringersi in affettuosa amicizia con il conterraneo Antonio Corradini, con cui intorno al 1743 si recò a Napoli per studiare l'arte barocca e visitare gli scavi archeologici di Ercolano.

Ben presto Piranesi iniziò a palesare un commosso entusiasmo davanti allo spettacolo delle «parlanti ruine» dei Fori Imperiali. «che di simili non arrivai di potermene mai formare sopra i disegni, benché accuratissimi che di queste stesse ha fatto l’immortale Palladio, che io pur sempre mi teneva inanzi agli occhi». Questo interesse per le antichità romane è attestato dall'esecuzione nel 1743 della Prima parte di architetture e prospettive inventate e incise da Gio. Batta Piranesi architetto veneziano; per realizzare questa raccolta di dodici tavole, dove già si impone per le sue notevoli capacità tecniche, Piranesi si consultò con la ricca biblioteca di Nicola Giobbe, per intercessione del quale riuscì anche ad entrare in contatto con Luigi Vanvitelli e Nicola Salvi.

 

Piranesi effettuò un primo bilancio della sua carriera artistica tra il 1744 e il 1747, quando spinto dalla mancanza di riconoscimenti e dalle pressanti condizioni economiche fece temporaneamente ritorno a Venezia. In questo soggiorno, peraltro scarsamente documentato, Piranesi probabilmente volle riflettere su quanto appena compiuto dal punto di vista artistico, anche in vista di scelte future: fu, inoltre, in rapporto con Giovan Battista Tiepolo e con il Canaletto, i quali lasciarono un'impronta profonda sulla sua fantasia. Alla fine, il Piranesi decise di dedicarsi al mestiere di incisore e di stabilirsi definitivamente a Roma, aprendo bottega propria a via del Corso, di fronte all'Accademia di Francia: si trattò di un scelta ben meditata, come osservato dallo studioso Henri Focillon che commentò: Accetta volutamente di essere un incisore perché capisce di poter realizzare così le sue ambizioni di architetto, archeologo e pittore.

 

Con il papato di Clemente XIII si moltiplicarono per l'artista gli incarichi e i riconoscimenti ufficiali. Eletto accademico onorario di San Luca nel 1761, e cavaliere dello Speron d'oro nel 1766, nel 1761 il Piranesi fu inviato dal Papa a studiare i restauri all'interno del Pantheon; due anni dopo, nel 1763, venne invece incaricato di intervenire sul piedistallo della colonna di Marco Aurelio con una statua della Giustizia e di modificare la zona absidale della basilica di San Giovanni in Laterano, edificio già restaurato da Francesco Borromini tra il 1646 e il 1649. Fu proprio mentre si occupava della chiesa lateranense che Piranesi ricevette la sua commessa architettonica più importante: si trattava della trasformazione della piccola chiesa di Santa Maria del Priorato e della piazza antistante, su commissione del cardinale Giovanni Battista Rezzonico, nipote del pontefice. Il cantiere si concluse nell'ottobre 1766 e restituì alla città di Roma un tempio caratterizzato da un austero ordine settecentesco, ma contraddittorio ed eccessivamente ornato, in linea con le teorie del suo progettista già espresse nel Parere su l'architettura (1765). In questi anni, inoltre, l'operosità del Piranesi si estese anche alla decorazione degli edifici della famiglia pontificia. È del 1767 la decorazione degli appartamenti al Quirinale e a Castel Gandolfo di monsignor Giovanni Battista, mentre nel 1768-69 Piranesi decorò l'appartamento in Campidoglio del senatore Abbondio, disegnando soffitti, arredi, e cornici di camini.

Il prestigio

All'inizio del suo definitivo insediamento il Piranesi, affascinato dalle antichità della Città Eterna, iniziò la produzione delle Vedute di Roma. Si trattava di una raccolta di tavole raffiguranti ruderi classici e monumenti antichi, anche esterni alla città (via Appia, Tivoli, Benevento) che gli assicurarono una cospicua remunerazione e anche rinomanza europea, grazie soprattutto al «grande formato delle tavole, al taglio sempre originale e prospetticamente accattivante delle composizioni, alla scelta mai scontata dei soggetti» (Treccani).

 

Si trattò questo di un periodo di profondo fermento artistico per il Piranesi, che al di là delle Vedute di Roma pubblicò diverse opere. In tal senso, si segnalano le Opere varie di architettura, prospettive, grotteschi, antichità sul gusto degli antichi romani, inventate e incise da Gio. Piranesi architetto veneziano (1750), le Camere sepolcrali degli antichi romani, le quali esistono dentro e fuori di Roma (fra il 1750 e il 1752), e la prima edizione delle Carceri, con il titolo Invenzioni capric di carceri all’acqua forte datte in luce da Giovani Buzard in Roma mercante al Corso (1745). Un cenno a parte va fatto per queste opere, pubblicate in due edizioni nel 1745 e nel 1761: insieme alle Vedute romane, le Carceri rappresentano l'opera più famosa, diffusa, e anche remunerativa di tutta la sua produzione. Tale celebrità va ricercata nella scelta di un soggetto assai caro al mondo barocco, ma reinterpretato enfatizzandone non solo il rimando alla romanità, bensì anche il carattere onirico e inquietante, talmente forte che le Carceri furono ritenute da Marguerite Yourcenar «una delle opere più segrete che ci abbia lasciato in eredità un uomo del XVIII secolo».

La notorietà di cui già allora il Piranesi godeva venne ulteriormente accresciuta nel periodo intercorso tra gli anni di pubblicazione delle due Carceri, ovvero il 1745 e il 1761. In questo arco di tempo, infatti, iniziò a diffondersi il fenomeno del grand tour, ovvero un lungo viaggio per le principali città d'interesse artistico e culturale dell'Europa continentale, considerato quasi d'obbligo allora per le persone del gran mondo: tappa fondamentale di questo giro era ovviamente Roma, con i suoi monumenti della civiltà antica e le sue prestigiose gallerie d'arte. In questo modo nell'Urbe si formò una cospicua comunità internazionale, e il Piranesi non tardò a diventare un punto di riferimento irrinunciabile della nuova vita artistica e intellettuale sorta in città. Importante fu l'amicizia con Thomas Hollis, gentiluomo britannico versato nelle arti presente in Italia nel 1751-53, che contribuì a consolidarne la fama e a diffonderne le opere; in virtù del prestigio raggiunto, e soprattutto grazie all'intercessione di Hollis, nel 1757 Piranesi venne perfino eletto membro onorario della Society of Antiquaries di Londra. Tra le amicizie legate al fenomeno di grand tour, comunque, si ricordano quella con l’architetto Robert Mylne, l'architetto scozzese Robert Adam, a Roma nel 1755-57 (cui Piranesi dedicò nel 1762 il Campo Marzio dell’antica Roma), l'architetto William Chambers, il pittore Thomas Jones; non mancò di fraternizzare anche con numerosi pittori francesi, fra cui Charles-Louis Clérisseau, Jean-Laurent Legeay, Jacques Gondoin, Charles de Wailly, Pierre-Louis Moreau-Desproux, e Pierre-Adrien Pâris.

Il pontificato di Clemente XIII

Intanto Roma serbava le tracce di un nuovo movimento artistico, sorto come reazione all'edonismo del rococò e caratterizzato da un ritorno alle forme classiche: si trattava del neoclassicismo, cui Piranesi conferì un personalissimo impulso grazie alla pubblicazione dei quattro volumi delle Antichità Romane, per un totale di 252 tavole. Importante fu l'ascesa al soglio pontificio nel 1758 del veneziano Clemente XIII, nato Carlo della Torre di Rezzonico, che ben presto divenne un munifico protettore e mecenate del Piranesi. Fu proprio sotto il suo pontificato - precisamente nel 1761, al tempo delle seconde Carceri - che l'artista pubblicò Della magnificenza e architettura de’ romani, saggio storico corredato di immagini teso a sostenere la supremazia dell'architettura romana su quella greca.

 

Con il papato di Clemente XIII si moltiplicarono per l'artista gli incarichi e i riconoscimenti ufficiali. Eletto accademico onorario di San Luca nel 1761, e cavaliere dello Speron d'oro nel 1766, nel 1761 il Piranesi fu inviato dal Papa a studiare i restauri all'interno del Pantheon; due anni dopo, nel 1763, venne invece incaricato di intervenire sul piedistallo della colonna di Marco Aurelio con una statua della Giustizia e di modificare la zona absidale della basilica di San Giovanni in Laterano, edificio già restaurato da Francesco Borromini tra il 1646 e il 1649. Fu proprio mentre si occupava della chiesa lateranense che Piranesi ricevette la sua commessa architettonica più importante: si trattava della trasformazione della piccola chiesa di Santa Maria del Priorato e della piazza antistante, su commissione del cardinale Giovanni Battista Rezzonico, nipote del pontefice. Il cantiere si concluse nell'ottobre 1766 e restituì alla città di Roma un tempio caratterizzato da un'austera eleganza neoclassica, squisitamente settecentesca, misurata nelle strutture e negli ornati. In questi anni, inoltre, l'operosità del Piranesi si estese anche alla decorazione degli edifici della famiglia pontificia. È del 1767 la decorazione degli appartamenti al Quirinale e a Castel Gandolfo di monsignor Giovanni Battista, mentre nel 1768-69 Piranesi decorò l'appartamento in Campidoglio del senatore Abbondio, disegnando soffitti, arredi, e cornici di camini.

 

Alla maturità più tarda appartengono Il Campo Marzio dell’antica Roma (1762) e le Diverse maniere di adornare i cammini (1769), dove è testimoniata l'intensa attività di Piranesi nella lucrosa commercializzazione di camini e oggetti decorativi, già rilevata nel 1770 dal pittore Vincenzo Brenna che affermò: «Piranesi ha fatto una raccolta così grande di marmi, che oltre avere riempito tutta la sua casa ha preso moltissime botteghe nella sua strada che sono anche piene, e per tutto si lavora e tiene da trenta persone il giorno a lavorare li suoi marmi, ha guasi lasciato da incidere, e si è buttato a traficare di marmi antichi». A quest'ultima opera si collega un'antologia di oggetti d'arredo denominata Vasi, candelabri, cippi che esercitò un'influenza notevole tra i gli orafi, i bronzisti e i lapicidi.

 

Giovan Battista Piranesi morì infine il 9 novembre 1778 a Roma, stroncato da una malattia nella sua casa in strada Felice (l'attuale n. 48 di via Sistina). Fu sepolto nella chiesa di Santa Maria del Priorato, da lui progettata, per volontà del cardinale Rezzonico, con la statua del defunto realizzata su commissione della famiglia dallo scultore Giuseppe Angelini; il sepolcro era adornato anche da un candelabro marmoreo predisposto dallo stesso artista, poi confiscato da Napoleone Bonaparte durante la campagna d'Italia e ricollocato nel Louvre, dove è tuttora esposto.

Concezione artistica e stile

L'eclettismo delle sue opere e la versatilità del suo estro creativo rendono Piranesi un artista difficilmente inseribile all'interno di una schematicità dettata da una suddivisione in stili o correnti artistiche. Personalità dalla duplice matrice culturale, veneziana e romana, Piranesi presenta una fisionomia artistica assai complessa, che si può scandire in tre componenti fondamentali.

 

L'arte di Piranesi, infatti, ha radici profondamente affondate nella tradizione del rococò, del quale egli rappresenta uno degli ultimi eredi. Quest'adesione al rococò è riscontrabile non solo nella qualità del disegno, sfatto ed evocatore, ma soprattutto nella natura stessa delle sue opere, che si configurano come invenzioni capricciose (come si legge nel frontespizio delle Carceri): con questa denominazione squisitamente rococò, infatti, Piranesi voleva indicare il carattere immaginoso e inconsueto delle proprie creazioni.

 

Il nucleo del discorso artistico di Piranesi si inserisce anche all'interno del neoclassicismo. Con la sensibilità neoclassica, infatti, Piranesi condivide l'impegno metodico e teorico e la passione per l'archeologia, maturata dopo la visita degli scavi di Ercolano. Questa caratteristica della poetica piranesiana fu rapidamente colta da Marguerite Yourcenar, che in un'opera commentò:

 

«L’autore delle Vedute e delle Antichità Romane non ha certo inventato né il gusto delle rovine, né l’amore per Roma. Un secolo prima di lui, anche Poussin e Claude Gelée [Claude Lorrain] avevano scoperto Roma con occhi nuovi di stranieri; la loro opera si era nutrita di quei luoghi inesauribili. Ma mentre per un Claude Gelée, per un Poussin, Roma era stata soprattutto il mirabile sfondo di una fantasticheria personale o di un discorso di ordine generale, ed un luogo sacro anche, accuratamente purificato da ogni contingenza contemporanea, situato a mezza strada dal divino paese della Favola, è l’Urbe stessa, sotto tutti i suoi aspetti e in tutte le sue implicazioni, dalle più banali alle più insolite, che Piranesi ha fissata ad un certo momento del XVIII secolo, nelle sue migliaia di tavole, insieme aneddotiche e visionarie. Non ha solo esplorato i monumenti antichi da disegnatore che cerchi una prospettiva da riprodurre; ne ha personalmente frugato i ruderi, un po’ per reperirvi le antichità di cui faceva commercio, ma soprattutto per penetrare il segreto delle loro fondazioni, per imparare e per dimostrare come vennero costruiti. È stato archeologo in un’epoca in cui il termine stesso non era in uso corrente»

Marguerite Yourcenar

Sul piano teorico, invece, Piranesi si discostò dall'ambiente neoclassico, sostenendo la superiorità della civiltà romana su quella greca. In opposizione alla fazione filoellenica di Johann Joachim Winckelmann, secondo cui la perfezione nell'arte fosse stata raggiunta solo dalla cultura greca (vista come fonte originaria di quella romana), Piranesi si schierò a favore degli antichi Romani. L'architettura romana, diceva Piranesi, era superiore in virtù delle notevoli capacità tecniche e dell'esuberanza creativa, opposte alla semplice uniformità di quella greca; sostenne, inoltre, che l'architettura romana dipendeva solo da quella etrusca, negandone gli aspetti derivativi dalla Grecia e sottolineandone le origini conseguentemente italiche.Questa polemica culminò con la pubblicazione del Parere su l'architettura (1765) dove due architetti, Protopiro e Didascalo, dibattono sui rispettivi meriti dell'architettura greca e di quella romana.

 

Ciò malgrado, risulta impossibile omologare l'opera del Piranesi al nascente neoclassicismo internazionale. In effetti l'artista veneto trae dalle colossali rovine il sentimento nuovo e nostalgico di un mondo ideale, incommensurabile e grandioso, ormai perduto e corroso: questo ne fa un precursore della sensibilità romantica. Piranesi, infatti, interpreta l'antichità classica allontanandosi dalla visione distaccata di Winckelmann: le opere antiche, per l'artista veneto, non suscitano pertanto una sensazione di quiete e distaccate riflessioni, bensì provocano forti emozioni. Ne è prova la sua opera grafica, dove la struttura monumentale delle vestigia classiche effigiate è interpretata alla luce di un'inquieta sensibilità decisamente preromantica.

 

Fortuna critica

Giovanni Battista Piranesi subì fasi alterne di apprezzamento e di aperta ostilità da parte degli intellettuali e degli artisti italiani e stranieri. Non conobbe, per esempio, una buona accoglienza presso Antonio Visentini che, oltre ad aver censurato la ristrutturazione della chiesa di Santa Maria del Priorato, definì Piranesi un «povero spensierato» che «pretende di esaltar Roma sopra la Grecia al somo, e la abasò per così dire al limo… [e] sempre intende le cose fuori del suo luoco senza posata considerazione». Una critica analoga gli fu rivolta dall'architetto inglese Richard Norris che, in visita a Santa Maria del Priorato nell'aprile 1772, annotò sul suo diario che «the Church is in my Opinion very bad, a strange composition of Ornaments that mean nothing– some of which, that is to say some small parts of the Ornaments, are good, but on the whole is a part of confusion».

 

Tra gli ammiratori più ferventi vi fu lo scrittore inglese Horace Walpole, che consigliò agli studenti inglesi di studiare «i sublimi sogni del Piranesi», dedicando al maestro italiano anche un lungo paragrafo ove scrisse:

 

«Selvaggio come Salvator Rosa, fiero come Michelangelo, esuberante come Rubens, ha immaginato scene... impensabili perfino nelle Indie. Costruisce palazzi sopra ponti, templi sui palazzi, scala il cielo con montagne di edifici»

 

In effetti, Piranesi fu uno degli iniziatori dell'immaginario gotico. Si dice, infatti, che le lugubri e vastissime carceri ideate da Piranesi avessero ispirato allo stesso Walpole la stesura de Il castello di Otranto, primo esempio di romanzo gotico, e la costruzione della sua villa di Strawberry Hill. Fu in particolare a partire dallo Sturm und Drang e dalla ricezione delle prime istanze romantiche che il culto di Piranesi si ravvivò: durante la stagione del Romanticismo, infatti, furono in molti ad apprezzare e amare l'opera grafica di Piranesi. Tra gli ammiratori più significativi si riportano Samuel Taylor Coleridge e Thomas de Quincey (che individuavano nelle visioni piranesiane una prova dell'identità di sogno e creazione), Victor Hugo, Charles Baudelaire, Aldous Huxley e Marguerite Yourcenar, che dedicò all'artista italiano un'intensa biografia.

 

L'interesse per Piranesi non scemò neanche nel corso del XX secolo, quando la sua produzione grafica fu sottoposta per la prima volta a uno studio filologico sistematico e scientifico, con la pubblicazione dei due cataloghi tuttora in uso (Focillon, 1918; Hind, 1922).Notevole fu in questo periodo l'influenza esercitata dalle tavole di Piranesi sulla produzione di Maurits Cornelis Escher (le cui costruzioni impossibili presentano un evidente debito alle Carceri) e sul Surrealismo

Da Wikipedia, l'enciclopedia libera.

di G. B. Piranesi;

Raccolta Foto de Alvariis;

Feeding

Roe deer are highly selective feeders which eat a wide variety of

plant types. They select highly nutritious plants and therefore

browse rather than graze. They enjoy herbs, cereals, hedgerow

plants, heather, and young trees as well as some garden plants.

All deer do not have a top set of front incisors, but instead have

a hard pad that acts to tear vegetation rather than cut it.

Social organisation

Roe deer are generally solitary animals usually seen alone or in

small family groups but can form larger informal groups when

feeding in open areas such as fields during the winter. They are

active throughout the day and night but are most likely to be

active at dawn and dusk. They can often be seen ‘lying up’ or

resting whilst ruminating much like farm animals such as cows

and sheep.

Breeding

Roe deer have a very interesting breeding system, which

is designed to ensure the best possible start in life for their

offspring. Females can give birth at two years old and will

normally produce one or two offspring (kids). Exceptionally they

may produce triplets. Young are born between late April and

June. Roe deer are unique amongst deer species in that they

delay the development of the fertilised egg prior to birth for

several months following mating. This is a mechanism adopted

to avoid birthing during harsh northern winters when survival of

young would be unlikely.

Bucks defend a territory, becoming increasingly aggressive

towards rivals, from April through to September. The ‘rut’ is the

term used for the breeding season that occurs between

mid-July and early August. During this time bucks will pursue

does and compete with neighbouring bucks to enlarge their

territories and increase their access to the does visiting the area.

Fights between males can be serious and may sometimes even

lead to fatalities

The cotton-top tamarin (Saguinus oedipus) is a small New World monkey weighing less than 0.5 kg (1.1 lb). This New World monkey can live up to 24 years, but most of them die by 13 years. One of the smallest primates, the cotton-top tamarin is easily recognized by the long, white sagittal crest extending from its forehead to its shoulders. The species is found in tropical forest edges and secondary forests in northwestern Colombia, where it is arboreal and diurnal. Its diet includes insects and plant exudates, and it is an important seed disperser in the tropical ecosystem.

 

The cotton-top tamarin displays a wide variety of social behaviors. In particular, groups form a clear dominance hierarchy where only dominant pairs breed. The female normally gives birth to twins and uses pheromones to prevent other females in the group from breeding. These tamarins have been extensively studied for their high level of cooperative care, as well as altruistic and spiteful behaviors. Communication between cotton-top tamarins is sophisticated and shows evidence of grammatical structure, a language feature that must be acquired.

 

Up to 40,000 cotton-top tamarins are thought to have been caught and exported for use in biomedical research before 1976, when CITES gave them the highest level of protection and all international commercial trade was prohibited. Now, the species is at risk due to large-scale habitat destruction, as the lowland forest in northwestern Colombia where the cotton-top tamarin is found has been reduced to 5% of its previous area. It is currently classified as critically endangered and is one of the rarest primates in the world, with only 6,000 individuals left in the wild.

 

Taxonomy and naming

S. oedipus has the common names "cotton-top tamarin" and "cotton-headed tamarin" in English. Its name comes from the white hair that spans its head and flows down past the neck. In Spanish, it is commonly called bichichi, tití pielroja, "tití blanco, tití cabeza blanca, or tití leoncito. In German-speaking areas, the cotton-top tamarin is commonly known as Lisztaffe (literally "Liszt monkey") due to the resemblance of its crest to the hairstyle of Hungarian composer and piano virtuoso Franz Liszt.

 

The species was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae. as Simia oedipus. Linnaeus chose the specific name oedipus, which means swollen foot, but as the species does not have particularly large feet, it is unknown why he chose this name. (Linnaeus often selected names from mythology without any particular rationale, and he may have used the name of Oedipus, the mythical Greek king of Thebes, more or less arbitrarily.) In 1977, Philip Hershkovitz performed a taxonomic analysis of the species based on fur coloration patterns, cranial and mandibular morphology, and ear size. He classified Geoffroy's tamarin S. geoffroyi as a subspecies of S. oedipus. Subsequent analyses by Hernández-Camacho and Cooper (1976), Russell Mittermeier and Coimbra-Filho (1981), and later Grooves (2001) consider the S. oedipus and S. geoffroyi types to be separate species.

 

Some researchers, such as Thorington (1976), posit that S. oedipus is more closely related to the white-footed tamarin (S. leucopus) than to S. geoffroyi. This view is supported by Hanihara and Natoria's analysis of toothcomb dental morphology (1987) and by Skinner (1991), who found similarities between S. oedipus and S. leucopus in 16 of 17 morphological traits considered.

 

This species of white-headed tamarin is thought to have diverged from the other Amazonian forms such as S. leucopus. This is supported by morphological considerations of the transition from juvenile to adulthood, during which the fur coloration patterns change. significantly and are similar between the two species. Hershkovitz proposed that the separation of the two species happened in the Pleistocene at the height of the Atrato River, where it intersected the Cauca-Magdalena. At that time, the area was covered by a sea, which created a geographic barrier that caused the species to diverge through the process of allopatric speciation. Today, the two species are principally separated by the Atrato River.

 

Physical characteristics

The cotton-top tamarin is part of the most diminutive family of monkeys, Callitrichidae, the marmosets and tamarins; it weighs 432 g (15.2 oz) on average. Its head–body length is 20.8–25.9 cm (8.2–10.2 in), while its tail—which is not prehensile—is slightly longer at around 33–41 cm (13–16 in). The species is not sexually dimorphic, the male and female are of a similar size and weight. Members of the Callitrichinae subfamily (including this species) have sharp nails (tegulae) on all digits except the big toes, which have the flat nails (ungulae) common to other primates. Tegulae resemble a squirrel's claws and help with movement through trees.

 

The cotton-top tamarin has a long sagittal crest, consisting of white hairs, from forehead to nape flowing over the shoulders. The skin of the face is black with gray or white bands located above the eyes. These bands continue along the edge of the face down to the jaw. Tamarins are generally divided into three groups by their facial characteristics: hairy-faced, mottled-faced, and bare-faced. The cotton-top tamarin has fine white hair covering its face, but they are so fine as to appear naked, thus it is considered a bare-faced tamarin. Its lower canine teeth are longer than its incisors, creating the appearance of tusks. Like other callitrichids, the cotton-top tamarin has two molar teeth on each side of its jaw, not three like other New World monkeys.

 

The cotton-top tamarin has fur covering all of the body except the palms of the hands and feet, the eyelids, the borders of the nostrils, the nipples, the anus, and the penis. The back is brown, and the underparts, arms, and legs are whitish-yellow. The rump and inner thighs and upper tail are reddish-orange. The fur is distributed with varying densities throughout the body: the genital region (scrotum and pubic zone), axilla, and the base of the tail have lower densities, while the forward region is much higher. Many individuals have stripes or whorls of fur of striking coloration on their throats. The cotton-top also has whiskers on its forehead and around its mouth.

 

Habitat and distribution

The cotton-top tamarin is restricted to a small area of northwest Colombia, between the Cauca and Magdalena Rivers to the south and east, the Atlantic coast to the north, and the Atrato River to the west. They are found exclusively in Colombia; 98% of their habitat has been destroyed. Historically, the entire area was suitable for the cotton-top tamarin, but due to habitat loss through deforestation, it survives in fragmented parks and reserves. One of the most important areas for the cotton-top is the Paramillo National Park, which consists of 460,000 hectares (1,800 sq mi) of primary and secondary forests.

 

The cotton-top tamarin is found in both primary and secondary forests, from humid tropical forests in the south of its range to tropical dry forests in the north. It is seldom found at altitudes above 400 m (1,300 ft), but has been encountered up to 1,500 m (4,900 ft). It prefers the lower levels of the tropical forests, but may also be found foraging on the ground and between the understory and the canopy. It can adapt to forest fragments and can survive in relatively disturbed habitats. In the dry forests are pronounced seasons. Between December and April, it is dry, while heavy rainfall occurs between August and November which can flood the forest floor. Across its range, annual rainfall varies between 500 and 1,300 mm (20 and 51 in).

 

Ecology

The cotton-top tamarin has a diet of mainly fruit (40%) and animal material (40%). This includes insects, plant exudates such as gum and sap, nectar, and occasionally reptiles and amphibians. Due to its small body size and high food passage rate, its diet must be high-quality and high-energy. Insectivory is common in the cotton-top and the species hunts for insects using a variety of methods: stealth, pouncing, chasing, exploring holes, and turning over leaves.

 

Tamarins act as seed dispersers in tropical ecosystems. While larger primates eat larger seeds, tamarins eat the smaller ones. The expelled seeds have a higher germination rate than others and ingesting larger seeds may help to dislodge and expel intestinal parasites.

 

The cotton-top tamarin is diurnal and sleeps with its social group in trees with foliage cover. The group leaves the sleeping tree together an hour after dawn and spends the day foraging, resting, travelling, and grooming. The species is thought to rise late and increases the speed of its foraging and travelling before dusk to avoid crepuscular and nocturnal predators. Its main predators include raptors, mustelids, felids, and snakes. The cotton-top tamarin is extremely vigilant, always looking for potential predators. When the group is resting, one individual moves apart and acts as a lookout to alert the group if it sees a threat.

 

Behavior

The cotton-top tamarin is a highly social primate that typically lives in groups of two to nine individuals, but may reach up to 13 members. These small familial groups tend to fluctuate in size and in composition of individuals and a clear dominance hierarchy is always present within a party. At the head of the group is the breeding pair. The male and female in this pair are typically in a monogamous reproductive relationship, and together serve as the group's dominant leaders.

 

Dominant pairs are the only breeding pair within their groups, and the female generally has authority over the breeding male. While nonbreeding group members can be the leading pair's offspring, immigrant adults may also live with and cooperate in these groups. This social grouping in cotton-top tamarins is hypothesized to arise from predation pressure. Cotton-top tamarins exhibit prosocial behavior that benefits other members of the group, and are well known for engaging in cooperative breeding whereby the group's subordinate adults help in rearing the offspring of the dominant pair. The dominant female is more likely to give birth to non-identical twins than a singleton, so it would be too energetically expensive for just one pair to raise the young.

 

To prevent younger, subordinate females within the group from breeding, the dominant female uses pheromones. This suppresses sexual behavior and delays puberty. Unrelated males that join the group can release the females from this reproductive suppression; this may result in more than one female of the group becoming pregnant, but only one of the pregnancies will be successful.

 

Cooperation

In cooperative breeding, the effort put into caring for the dominant breeders' offspring is shared by the group members. Parents, siblings, and immigrant adults share young rearing duties for the breeding pair's young. These duties include carrying, protecting, feeding, comforting, and even engaging in play behavior with the group's young. Cotton-top tamarins display high levels of parental investment during infant care. Males, particularly those that are paternal, show greater involvement in caregiving than do females. Despite this, both male and female infants prefers contact and proximity to their mothers over their fathers. Males may invest additional support in rearing offspring as a form of courtship to win the favor of the group's dominant female. However, evidence indicates that time spent carrying infants does not correlate with a male's overall copulation frequency.

 

Since only one female in a group breeds, heavy investment in infant care ensures that all offspring survive until independence. Accordingly, cotton-top tamarins bear excessive costs to care for the group's young. Male carriers, especially paternal carriers, incur large energetic costs for the sake of the group's young. This burden may cause some male cotton-tops to lose up to 10–11% of their total body weight. The large weight loss may occur from reduced food intake as infant-carrying inhibits foraging ability for a carrier. The trend of male-carrier weight loss and decreased food intake is in contrast to the dominant female's periovulatory period, when she gains weight after increasing her own food intake and relinquishing much of her infant-carrying duties.

 

Altruism

While caregiving by males appears to be altruistic, particularly in cotton-top sires, the costs of infant care may in fact be tolerated for selfish reasons. Namely, the costs to male weight and foraging ability may, in turn, promote consecutive pregnancies in dominant females, thereby providing more offspring bearing the sire's genes. Additionally, the cooperative breeding structure of cotton-tops can change with group size and parental experience. First-time sires spend a greater amount of time carrying the infant than experienced ones, and in smaller groups, sires do a greater proportion of carrying and feeding the infant than in larger groups, where helpers take on more of the work. Total care for infants remains constant with varying group size, and infant outcome is not significantly different in groups that have differing levels of experience in raising offspring.

  

Once infants reach sufficient age, they permanently leave the backs of their carriers and begin contributing to the group.

The cooperative breeding hypothesis predicts that cotton-top tamarins engage with this young-rearing paradigm, and in turn, naturally embrace patterns of prosocial behavior. These monkeys engage in such behavior by acting altruistically within their groups in caring for infants, vocalizing alarm calls, and in sharing food. Though some studies indicate that cotton-top tamarins have the psychological capacity to participate in reciprocally mediated altruism, it is unclear whether the cotton-top tamarin acts solely using judgments on reinforcement history.

 

Other studies involving cotton-top tamarins have hinted that positive reciprocity and reciprocal altruism are irrelevant in the prosociality of these primates. Some researchers believe these primates tend to cooperate for selfish reasons and in situations where they incur some benefit for themselves. That is, cooperation in cotton-top tamarins can be better described by mutualism than by true altruism.

 

Tamarins in captivity have shown the ability to distinguish other individuals based on cooperative tendencies and past behavior. Cotton-tops ultimately use this information to guide future cooperation. Brief periods of defection tend to cause swift, irreparable breakups between these primates and their cooperators. To avoid this, cotton-top tamarins may make economically driven decisions based on the projected incentives of a potential cooperator.

 

Spite and aggression

Despite an expansive array of altruistic behaviors, cotton-top tamarins engage in great bouts of spite through negative reciprocity and punishment. They have been observed to immediately start denying cooperation with monkeys that deny them benefits. Further, in captivity, these primates are not observed to increase altruistic behavior with fellow primates that are committed fully to cooperation. Based on this, researchers believe that repeated interactions in a cooperative society like that of the cotton-top tamarin can heighten the chances that an individual will designate behavioral punishments to others in its group. This reaction has also been observed in other species. However, these reciprocal punishments, or relative lack of altruistic actions, may alternatively happen as a result of response facilitation that increases the chances of a cotton-top punishing another primate after watching that individual perform a similar action.

 

Another way to look at punishment in cotton-top tamarins is by observing their aggressive behavioral responses within and between groups, as well as between species. The cotton-top tamarin, like many marmosets, other tamarins, and specifically those in the genus Saguinus, stages aggressive displays almost exclusively towards fellow monkeys that belong to the same gender. These intrasexual displays of aggression are more frequent in females, and are vital when a breeding female is forcing both subadult and adult females to emigrate out of a familial group.

 

Though aggression can occur within groups, the response towards intruders of another species is much more drastic and can involve a sexual dimorphism in displays. Females typically employ scent-marking intruder response tactics, whereas males are more prone to vocalizing threats, physical aggression, and piloerection. Scent-marking in cotton-top tamarins is done in two ways: either using anogenital scent-marking, or suprapubic scent-marking. The ability to use both of these separate glandular fields for threat signals may indicate females have developed diverging evolutionary threats through differential use of these markings. These variable signals may be used to sign a territorial encounter, or serve as a reproductive signal. The intensity of female threats is generally comparable when directed at intruders of either gender. In contrast, male cotton-tops are considerably more threatening towards fellow males than towards females.

 

Communication

The cotton-top tamarin vocalizes with bird-like whistles, soft chirping sounds, high-pitched trilling, and staccato calls. Researchers describe its repertoire of 38 distinct sounds as unusually sophisticated, conforming to grammatical rules. Jayne Cleveland and Charles Snowdon performed an in-depth feature analysis to classify the cotton-top's repertoire of vocalizations in 1982. They concluded that it uses a simple grammar consisting of eight phonetic variations of short, frequency-modulated "chirps"—each representing varying messages—and five longer constant frequency "whistles". They hypothesize that some of these calls demonstrate that the cotton-top tamarin uses phonetic syntax, while other calls may be exemplars of lexical syntax usage. Each type of call is given a letter signifier; for example, C-calls are associated with finding food and D-calls are associated with eating. Further, these calls can be modified to better deliver information relevant to auditory localization in call-recipients. Using this range of vocalizations, the adults may be able to communicate with one another about intention, thought processes, and emotion, including curiosity, fear, dismay, playfulness, warnings, joy, and calls to young.

 

Language acquisition

Over the first 20 weeks, after a cotton-top tamarin is born, it is not fully capable of producing the range of vocalizations that an adult monkey can. Despite this limitation on speech producibility, researchers believe that language acquisition occurs early on with speech comprehension abilities arising first. Infants can at times produce adult-like chirps, but this is rarely done in the correct context and remains inconsistent across the first 20 weeks of life. Regardless, infant cotton-tops are able to respond in behaviorally appropriate ways to varying contexts when presented with adult chirps. This indicates that verbal perception is a quickly acquired skill for offspring, followed closely by auditory comprehension, and later by proper vocal producibility.

 

Castro and Snowdon (2000) observed that aside from inconsistent adult-like chirping, cotton-top infants most often produce a prototype chirp that differs in vocalization structure from anything seen in the full adult range of vocalizations. Infants are thought to imitate adult speakers, which use differing calls in various contexts, but by using solely the infant prototypical chirp. For instance, adult cotton-tops are known to significantly reduce the amount of general alarm calling in the presence of infants.[ This is likely adapted so that adults in close proximity to the groups young do not attract the attention of predators to infant-dense areas. Additionally, infants reduce their prototype chirping in the presence of predators. Whether infants are shadowing the calling behavior of adults or they are comprehending danger remains unclear. However, researchers argue that young cotton-top tamarins are able to represent semantic information regardless of immature speech production.

 

To confirm the notion that language acquisition occurs as a progression of comprehension before production, Castro and Snowdon (2000) showed that infants respond behaviorally to vocalizing adults in a fashion that indicates they can comprehend auditory inputs. When an adult produces a C-call chirp, used to indicate food preference and when navigating to a food source, an infant approaches the adult caller to be fed, but do not use the prototype calling as a proxy for C-calls. This finding argues for the idea that infants are able to understand vocalizations first, and later acquire the ability to communicate with adult vocalizations.

 

General calling

Among the typical cotton-top tamarin communicative vocalizations, the combination long call (CLC) and the alarm call (AC) are the most heavily represented in the literature. CLCs encompass a range of contact calls that are produced by isolated individuals using chirps and whistles. This type of call is also used for seemingly altruistic alarm calls, thus adding to its range of cooperative behaviors. It is issued in the presence of kin when a threatening llamas predator is seen. Predators of the cotton-top tamarin include snakes, ocelots, tayras, and most notably, hawks. Early observations by Patricia Neyman even showed that cotton-tops produce diverse sets of alarm calls that can discriminate the presence of birds of prey versus ground-based predators.

 

CLCs involve the production of complex sequence multisyllabic vocalizations. Researchers have argued that long calls exhibit individual differences, thus can carry information sufficient for recipients to determine caller identity. Using habituation-discrimination paradigms in language experiments, this theory has been confirmed multiple times in literature. However, the individual syllables within a complete CLC vocalization in isolation of each other do not transfer sufficient information to communicate messages between monkeys. Scientists thus consider the whole, intact string of vocalizations to be the unit of perception for CLCs in the cotton-top tamarin. These examinations may confirm that cotton-tops incorporate a lexical syntax in areas of their communication.

 

Since tamarins can discriminate between predatory threats using varying vocalizations, recipients of an AC are thought to extract various complex signals from this form of communication. Primarily, cotton-tops are able to glean the identity of the cooperating tamarin through differences in individuals' alarm calls. Further, adults are able to discriminate the gender of callers from their ACs and determine the range of calls within a related tamarin's alarm calling repertoire. Alarm call-based identification is postulated to play a number of functional roles in the cotton-top tamarin. Firstly, an AC recipient is able to identify a cooperating tamarin, and by recognizing which in their group it is, be able to judge the reliability of the AC from past experience. This may arise from a selective pressure for being able to statistically determine the amount of risk present, and how endangered an individual and its group are.

 

Additionally, being able to localize auditory signals may help determine predator location, especially in the presence of a second AC from a different tamarin in the group. This can help confirm predator presence, type (e.g. flying versus ground-based), and support the recipient in triangulating a predator's location. In the context of the cotton-top's cooperative breeding groups, this is postulated as being adaptive for determining the variable risk to one's group members. For example, a call recipient is able to determine which of its kin are and are not at risk (e.g. young offspring, mates, subordinates, relatives, carriers, etc.) and plan subsequent actions accordingly.

 

Food calls

The cotton-top tamarin makes selective, specialized vocalizations in the presence of food. These include the C-call, produced when a cotton-top approaches and sorts through food, and the D-call, which is associated with food retrieval and is exhibited while eating.

 

C-call chirping is believed to be an honest signal for communicating food preference, and a cotton-top tamarin more often and more rapidly vocalizes with these chirps when approaching a highly favored food source. Functionally, this behavior may inform other tamarins of the actions the caller will take in a feeding context and whether a preferable food source is available. Despite this research indicating that food calls may be informative to fellow group mates, other observations of cotton-tops show that quantity and distribution of food and audience do not significantly alter a caller's food-centered vocalizations.

 

The cotton-top tamarin is seen to produce food calls both in the presence and absence of group members. Additionally, response to food calls are directed back to an original caller independent of visual confirmation of a food source. While this may appear to be a result of a very primitive form of communication, Roush and Snowdon (2005) maintain that the food-calling behavior confers some mentally representable information about food to recipient tamarins.

 

Conservation status

The wild population is estimated at 6,000 individuals, with 2,000 adults. This species is critically endangered, and was listed in "The World's 25 Most Endangered Primates between 2008 and 2012." The publication lists highly endangered primate species and is released every two years by the International Union for Conservation of Nature Species Survival Commission Primate Specialist Group. The cotton-top tamarin was not selected for the 2012–2014 publication.

  

The species is critically endangered, with a wild population of merely 6,000 individuals including about 2,000 free-roaming adults.

Habitat destruction through forest clearing is the main cause of this collapse, and the cotton-top has lost more than three-quarters of its original habitat to deforestation, while the lowland forest in which it lives has been reduced to 5% of its historical range. This land is then used for large-scale agricultural production (i.e. cattle) and farming, logging, oil palm plantations, and hydroelectric projects that fragment the cotton-top tamarin's natural range.

 

The illegal pet trade and scientific research have also been cited as factors by the IUCN. While biomedical studies have recently limited their use of this species, illegal capture for the pet trade still plays a major role in endangering the cotton-top. Before 1976, when CITES listed the species under Appendix I banning all international trade, the cotton-top tamarin was exported for use in biomedical research.

 

In captivity, the cotton-top is highly prone to colitis, which is linked to an increased risk of a certain type of colon cancer. Up to 40,000 individuals were caught and exported for research into those diseases, as well as Epstein-Barr virus, for the benefit of humans. The species is now protected by international law. Although enough individuals are in captivity to sustain the species, it is still critically endangered in the wild.

 

The Proyecto Tití ("Project Tamarin") was started in 1985 to provide information and support in conservation of the cotton-top tamarin and its habitat in northern Colombia. Proyecto Tití's programs combine field research, education, and community programs to spread awareness about this endangered species and encourage the public to participate in its protection. It now has partner status with the Wildlife Conservation Network.

 

In January 2015, two captive cotton-top tamarins at the Alexandria Zoological Park in Alexandria, Louisiana, died when a caretaker left them outside overnight in temperatures as low as 30 °F. One other individual survived.

Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.

 

The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.

 

The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.

 

Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.

 

There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.

 

Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.

 

Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.

 

Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.

 

Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.

 

Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.

 

All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.

 

Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.

 

After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.

 

Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.

 

Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).

 

Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.

 

Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.

 

Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.

 

Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).

 

Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.

 

So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).

 

Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.

 

The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.

 

Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.

 

In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.

 

Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.

 

Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.

 

Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.

 

The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.

 

The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.

 

The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.

 

The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.

 

The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.

 

Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.

 

Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.

 

Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.

 

The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.

 

The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.

 

Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.

 

Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.

 

Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.

 

The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.

 

Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.

 

Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.

 

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.

 

The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.

 

The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.

 

The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.

 

The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).

 

The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.

 

Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.

 

There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.

 

Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.

 

Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.

 

As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.

 

The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).

 

The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.

 

Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.

 

Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.

 

Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.

 

Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.

 

A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.

 

An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.

  

The brown-throated sloth (Bradypus variegatus) is a species of three-toed sloth found in the neotropical ecozone.

 

It is the most common of the four species of three-toed sloth, and is found in the forests of South and Central America.

 

The brown-throated sloth is of similar size and build to most other species of three-toed sloth, with both males and females being 42 to 80 centimetres (17 to 31 in) in total body length. The tail is relatively short, only 2.5 to 9 cm (1.0 to 3.5 in) long. Adults weigh from 2.25 to 6.3 kg (5.0 to 13.9 lb), with no significant size difference between males and females. Each foot has three fingers, ending in long, curved claws, which are 7 to 8 cm (2.8 to 3.1 in) long on the fore feet, and 5 to 5.5 cm (2.0 to 2.2 in) on the hind feet.

 

The head is rounded, with a blunt nose and inconspicuous ears. As with other sloths, the brown-throated sloth has no incisor or canine teeth, and the cheek teeth are simple and peg-like. They have no gall bladder, cecum, or appendix.

 

The brown-throated sloth has grayish-brown to beige-color fur over the body, with darker brown fur on the throat, the sides of the face, and the forehead. The face is generally paler in colour, with a stripe of very dark fur running beneath the eyes.

 

The guard hairs are very coarse and stiff, and overlie a much softer layer of dense under-fur. The hairs are unusual in lacking a central medulla, and have numerous microscopic cracks across their surfaces. These cracks are host to a number of commensal species of algae, including Rufusia pillicola, Dictyococcus bradypodis, and Chlorococcum choloepodis. The algae are generally absent in the hair of young sloths, and may also be absent in particularly old individuals, where the outer cuticle of the hair has been lost. Sloth hair also harbours a rich fungal flora.

 

Over parts of its range, the brown-throated sloth overlaps the range of Hoffmann's two-toed sloth. Where this overlap occurs, the three-toed sloth tends to be smaller and more numerous than its relative, being more active in moving through the forest and maintaining more diurnal activity.

 

This image was taken in near Lake Maica, close to Santarem, along the Amazon River in Brazil. The Sloth was very very slowly climbing down from the top of the tree.

Giovanni Battista Cipriani

Giovanni Battista Cipriani (Firenze, 1727 – Hammersmith e Fulham, 14 dicembre 1785) è stato un pittore, disegnatore e docente italiano.

Biografia

Giovanni Battista Cipriani, o Cypriani, studiò prima all'Accademia di belle arti di Firenze con il pittore, collezionista e mercante d'arte pisano Ignazio Hugford - un allievo di Anton Domenico Gabbiani - poi, dal 1750, a Roma dove si diffondeva il gusto del neoclassicismo, sull'esempio di Pompeo Batoni e del pittore e critico d'arte tedesco Anton Raphael Mengs. A Firenze dipinse nel 1754 il tendone dell'organo della Chiesa di Santa Maria Maddalena dei Pazzi. Una sua pala d'altare oggi è nella Chiesa di San Bartolomeo in Pantano, a Pistoia.

 

Ad agosto 1755 seguì a Londra lo scultore Joseph Wilton, l'architetto William Chambers e lo scultore fiorentino Giovanni Battista Capezzuoli. Nel 1761 sposò un'inglese ed ebbe tre figli, tra cui Henry - morto a Londra il 17 settembre 1820 - che fu pittore.

 

Nel 1758 assunse l'incarico di seguire gli apprendisti pittori nella galleria londinese del duca di Richmond ed ebbe come allieva la pittrice e cantante inglese Emma Jane Greenland. Egli fu uno dei quaranta fondatori della Royal Academy of Arts e disegnò anche il diploma dell'accademia, inciso da Francesco Bartolozzi. Presentò sue opere, con soggetti mitologici e storici, in occasione delle esposizioni annuali della Royal Academy che oggi possiede una raccolta di opere di Cipriani su carta.

 

Lord Tilney lo incaricò di decorare con affreschi illusionistici la propria country house, Wanstead, nell'Essex, una residenza in stile palladiano che era stata progettata da Campbell e fu poi demolita nel 1822. Cipriani decorò anche la nuova Somerset House, sullo Strand, il capolavoro dell'architetto Chambers e la Syon House, progettata dall'architetto scozzese Robert Adam. Rivestiva le mura con personaggi fiabeschi, amorini, danzatrici, allegorie, soggetti mitologici. I suoi disegni venivano anche trasferiti sui mobili e questo gusto neoclassico si mantenne intatto, in Inghilterra, fino alla fine dell'Ottocento.

 

Su incarico di George Walpole decorò nel 1781 la palladiana Houghton Hall e nel 1783 dipinse tre tele, ispirate al mondo dell'antica Greciaː Filottete a Lemno, Castore e Polluce e Edipo a Colono.

 

Giorgio III lo incaricò di decorare, con figure allegoriche e mitologiche, l'esterno della carrozza reale da parata, realizzata su progetto di Chambersː la Gold State Coach, ancora oggi usata in occasione di nozze della famiglia regnante inglese. Di questa carrozza restano tre disegni del 1760, di Chambers e di Cipriani, di cui uno è nelle Royal Mews, Buckingham Palace, dove si può vedere la carrozza, e gli altri sono nella Royal Library del castello di Windsor. Il modellino in cera, di Giovanni Battista Capezzuoli e J. Voyez, dipinto da Cipriani, è al London Museum. Per Giorgio III Cipriani dipinse anche un padiglione, costruito su disegno di Chambers e di Adam nei giardini di Richmond, (Surrey), per la festa in onore di Cristiano VII di Danimarca, il 24 settembre 1768.

 

Molti suoi disegni furono trasferiti su lastra e poi stampati, nella maggior parte dei casi dal suo amico Francesco Bartolozzi, oppure da Richard Earlom.

 

Oltre a soggetti allegorici, storici o mitologici, o che si riferiscono al Vecchio o del Nuovo Testamento, o a scene di genere, Cipriani eseguì anche disegni decorativi per cartoncini d'invito, per biglietti d'ingresso a spettacoli teatrali o musicali, per ex libris. Illustrò libri, tra cui L'Orlando furioso, edito da J. Baskerville a Birmingham nel 1773 e il libro curato da Giuspanio Graglia, Tutti gli epigrammi di M. Val. Marziale, stampato a Londra nel 1783.

 

Cipriani lasciò per testamento il suo Autoritratto a pastelli agli Uffizi e un altro Autoritratto, disegnato, è conservato nel Gabinetto di disegni e stampe degli Uffizi. Cipriani è raffigurato nel grande quadro del pittore tedesco Johann Zoffany, insieme agli altri fondatori della Royal Academy. Un suo pastello che rappresenta Cleopatra è nel City Museum and Art Gallery di Plymouth. Un migliaio, tra disegni, pastelli e acquarelli, si trovavano in casa dell'artista, al momento della sua morte: furono tutti venduti all'asta nel 1786, come i dipinti, quindi le sue opere furono disperse e oggi si trovano in raccolte pubbliche e private.

 

Da non confondere con l'incisore senese, Giovanni Battista Cipriani (1766-1839) che operò in modo particolare su soggetti romani, musicali e teatrali.

Da Wikipedia, l'enciclopedia libera.

disegno di Giovanni Battista Cipriani;

Raccolta Foto de Alvariis

Island of Madagascar

Off The East Coast Of Africa

Palmarium Reserve

 

Click On Image To Enlarge.

 

Red ruffed lemur high in a tree.

 

The red ruffed lemur (Varecia rubra) is one of two species in the genus Varecia, the ruffed lemurs; the other is the black-and-white ruffed lemur (Varecia variegata). Like all lemurs, it is native to Madagascar and occurs only in the rainforests of Masoala, in the northeast of the island.

 

It is one of the largest primates of Madagascar with a body length of 53 cm, a tail length of 60 cm and a weight of 3.3–3.6 kg. Its soft, thick fur is red and black in colour and sports a buff or cream colored spot at the nape, but a few are known to have a white or pink patch on the back of the limbs or digits and a ring on the base of the tail in a similar color.

 

The red ruffed lemur is a very clean animal and spends a lot of time grooming itself and in social grooming. The lower incisors (front teeth) and the claw on the second toe of the hind foot are specially adapted for this behavior. The lower incisors grow forward in line with each other and are slightly spaced. This creates a toothcomb which can be used to groom its long, soft fur. The claw is also used for grooming.

 

The red ruffed lemur lives 15–20 years in the wild. In captivity, 25 years is not uncommon, and one lived to be about 33 years old. It is a diurnal animal, and most active in the morning and evening.

 

The red ruffed lemur is mainly a fruit-eater, though it is known to eat leaves and shoots. They especially like figs. - source Wikipedia

Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.

 

The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.

 

The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.

 

Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.

 

There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.

 

Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.

 

Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.

 

Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.

 

Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.

 

Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.

 

All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.

 

Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.

 

After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.

 

Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.

 

Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).

 

Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.

 

Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.

 

Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.

 

Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).

 

Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.

 

So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).

 

Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.

 

The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.

 

Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.

 

In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.

 

Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.

 

Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.

 

Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.

 

The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.

 

The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.

 

The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.

 

The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.

 

The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.

 

Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.

 

Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.

 

Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.

 

The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.

 

The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.

 

Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.

 

Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.

 

Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.

 

The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.

 

Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.

 

Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.

 

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.

 

The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.

 

The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.

 

The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.

 

The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).

 

The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.

 

Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.

 

There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.

 

Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.

 

Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.

 

As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.

 

The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).

 

The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.

 

Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.

 

Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.

 

Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.

 

Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.

 

A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.

 

An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.

 

Although a great many fossil fishes have been found and described, they represent a tiny portion of the long and complex evolution of fishes, and knowledge of fish evolution remains relatively fragmentary. In the classification presented in this article, fishlike vertebrates are divided into seven categories, the members of each having a different basic structural organization and different physical and physiological adaptations for the problems presented by the environment. The broad basic pattern has been one of successive replacement of older groups by newer, better-adapted groups. One or a few members of a group evolved a basically more efficient means of feeding, breathing, or swimming or several better ways of living. These better-adapted groups then forced the extinction of members of the older group with which they competed for available food, breeding places, or other necessities of life. As the new fishes became well established, some of them evolved further and adapted to other habitats, where they continued to replace members of the old group already there. The process was repeated until all or almost all members of the old group in a variety of habitats had been replaced by members of the newer evolutionary line.

 

The earliest vertebrate fossils of certain relationships are fragments of dermal armour of jawless fishes (superclass Agnatha, order Heterostraci) from the Upper Ordovician Period in North America, about 450 million years in age. Early Ordovician toothlike fragments from the former Soviet Union are less certainly remains of agnathans. It is uncertain whether the North American jawless fishes inhabited shallow coastal marine waters, where their remains became fossilized, or were freshwater vertebrates washed into coastal deposits by stream action.

 

Jawless fishes probably arose from ancient, small, soft-bodied filter-feeding organisms much like and probably also ancestral to the modern sand-dwelling filter feeders, the Cephalochordata (Amphioxus and its relatives). The body in the ancestral animals was probably stiffened by a notochord. Although a vertebrate origin in fresh water is much debated by paleontologists, it is possible that mobility of the body and protection provided by dermal armour arose in response to streamflow in the freshwater environment and to the need to escape from and resist the clawed invertebrate eurypterids that lived in the same waters. Because of the marine distribution of the surviving primitive chordates, however, many paleontologists doubt that the vertebrates arose in fresh water.

 

Heterostracan remains are next found in what appear to be delta deposits in two North American localities of Silurian age. By the close of the Silurian, about 416 million years ago, European heterostracan remains are found in what appear to be delta or coastal deposits. In the Late Silurian of the Baltic area, lagoon or freshwater deposits yield jawless fishes of the order Osteostraci. Somewhat later in the Silurian from the same region, layers contain fragments of jawed acanthodians, the earliest group of jawed vertebrates, and of jawless fishes. These layers lie between marine beds but appear to be washed out from fresh waters of a coastal region.

 

It is evident, therefore, that by the end of the Silurian both jawed and jawless vertebrates were well established and already must have had a long history of development. Yet paleontologists have remains only of specialized forms that cannot have been the ancestors of the placoderms and bony fishes that appear in the next period, the Devonian. No fossils are known of the more primitive ancestors of the agnathans and acanthodians. The extensive marine beds of the Silurian and those of the Ordovician are essentially void of vertebrate history. It is believed that the ancestors of fishlike vertebrates evolved in upland fresh waters, where whatever few and relatively small fossil beds were made probably have been long since eroded away. Remains of the earliest vertebrates may never be found.

 

By the close of the Silurian, all known orders of jawless vertebrates had evolved, except perhaps the modern cyclostomes, which are without the hard parts that ordinarily are preserved as fossils. Cyclostomes were unknown as fossils until 1968, when a lamprey of modern body structure was reported from the Middle Pennsylvanian of Illinois, in deposits more than 300 million years old. Fossil evidence of the four orders of armoured jawless vertebrates is absent from deposits later than the Devonian. Presumably, these vertebrates became extinct at that time, being replaced by the more efficient and probably more aggressive placoderms, acanthodians, selachians (sharks and relatives), and by early bony fishes. Cyclostomes survived probably because early on they evolved from anaspid agnathans and developed a rasping tonguelike structure and a sucking mouth, enabling them to prey on other fishes. With this way of life they apparently had no competition from other fish groups. Cyclostomes, the hagfishes and lampreys, were once thought to be closely related because of the similarity in their suctorial mouths, but it is now understood that the hagfishes, order Myxiniformes, are the most primitive living chordates, and they are classified separately from the lampreys, order Petromyzontiformes.

 

Early jawless vertebrates probably fed on tiny organisms by filter feeding, as do the larvae of their descendants, the modern lampreys. The gill cavity of the early agnathans was large. It is thought that small organisms taken from the bottom by a nibbling action of the mouth, or more certainly by a sucking action through the mouth, were passed into the gill cavity along with water for breathing. Small organisms then were strained out by the gill apparatus and directed to the food canal. The gill apparatus thus evolved as a feeding, as well as a breathing, structure. The head and gills in the agnathans were protected by a heavy dermal armour; the tail region was free, allowing motion for swimming.

 

Most important for the evolution of fishes and vertebrates in general was the early appearance of bone, cartilage, and enamel-like substance. These materials became modified in later fishes, enabling them to adapt to many aquatic environments and finally even to land. Other basic organs and tissues of the vertebrates—such as the central nervous system, heart, liver, digestive tract, kidney, and circulatory system— undoubtedly were present in the ancestors of the agnathans. In many ways, bone, both external and internal, was the key to vertebrate evolution.

 

The next class of fishes to appear was the Acanthodii, containing the earliest known jawed vertebrates, which arose in the Late Silurian, more than 416 million years ago. The acanthodians declined after the Devonian but lasted into the Early Permian, a little less than 280 million years ago. The first complete specimens appear in Lower Devonian freshwater deposits, but later in the Devonian and Permian some members appear to have been marine. Most were small fishes, not more than 75 cm (approximately 30 inches) in length.

 

We know nothing of the ancestors of the acanthodians. They must have arisen from some jawless vertebrate, probably in fresh water. They appear to have been active swimmers with almost no head armour but with large eyes, indicating that they depended heavily on vision. Perhaps they preyed on invertebrates. The rows of spines and spinelike fins between the pectoral and pelvic fins give some credence to the idea that paired fins arose from “fin folds” along the body sides.

 

The relationships of the acanthodians to other jawed vertebrates are obscure. They possess features found in both sharks and bony fishes. They are like early bony fishes in possessing ganoidlike scales and a partially ossified internal skeleton. Certain aspects of the jaw appear to be more like those of bony fishes than sharks, but the bony fin spines and certain aspects of the gill apparatus would seem to favour relationships with early sharks. Acanthodians do not seem particularly close to the Placodermi, although, like the placoderms, they apparently possessed less efficient tooth replacement and tooth structure than the sharks and the bony fishes, possibly one reason for their subsequent extinction.

The Mursi (also called Murzu) is the most popular tribe in the southwestern Ethiopia lower Omo Valley, 100 km north of Kenyan. They are estimated to 10 000 people and live in the Mago National Park, established in 1979. Due to the climate, they move twice a year between the winter and summer months. They herd cattle and grow crops along the banks of the Omo River. The Mursi are sedentary rather than nomadic. Their language belongs to the Nilo-Saharan linguistic family.Very few Mursi people speak Amharic, the official Ethiopian language. Although a small percentage of the Mursi tribe are Christians, most still practice animism. Mursi women wear giant lip plate, a sign of beauty, like in Suri tribe, and also a prime attraction for tourists which help to sustain a view of them, in guidebooks and travel articles, as an untouched people, living in one of the last wildernesses of Africa. When they are ready to marry, teenagers start to make a hole in the lower lip with a wood stick.

It will be kept for one night, and is removed to put a bigger one. This is very painful at this time. Few months after, the lip plate has its full size, and the girl is seen as beautiful by the men. The lip plate is made of wood or terracotta. They have to remove the lower incisors to let some space for the disc. Sometimes the lip is broken by the pressure of the plate. This is a big problem for the girl because men will consider her as ugly, she won't be able to marry anyone in the tribe apart the old men or the sick people. Women and men are shaved because they hate hairiness. Both like to make scarifications on their bodies. Women as a beauty sign, men after killing animals or ennemies as competition for grazing land has led to tribal conflicts.

The Mursi men have a reputation for being aggressive and are famous for their stick fighting ceremony called donga. The winner of the donga will be able to select the girl of his choice to have relations with if she agrees. Similar to the Surma tribe, the Mursi tribe commonly drink a mixture of blood and milk. Over the past few decades they and their neighbours have faced growing threats to their livelihoods cause the Ethiopian government officials have been actively evicting Mursi people from the Omo National Park, without any compensation to rent their land to foreign investors. Drought has made it difficult for many families to feed themselves by means of their traditional mix of subsistence activities. The establishment of hunting concessions has added to the pressure on scarce ressources.

 

© Eric Lafforgue

www.ericlafforgue.com

 

Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.

 

The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.

 

The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.

 

Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.

 

There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.

 

Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.

 

Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.

 

Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.

 

Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.

 

Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.

 

All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.

 

Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.

 

After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.

 

Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.

 

Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).

 

Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.

 

Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.

 

Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.

 

Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).

 

Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.

 

So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).

 

Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.

 

The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.

 

Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.

 

In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.

 

Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.

 

Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.

 

Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.

 

The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.

 

The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.

 

The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.

 

The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.

 

The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.

 

Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.

 

Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.

 

Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.

 

The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.

 

The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.

 

Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.

 

Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.

 

Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.

 

The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.

 

Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.

 

Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.

 

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.

 

The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.

 

The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.

 

The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.

 

The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).

 

The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.

 

Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.

 

There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.

 

Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.

 

Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.

 

As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.

 

The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).

 

The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.

 

Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.

 

Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.

 

Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.

 

Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.

 

A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.

 

An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.

  

UN MONUMENTO ALL'AMICIZIA E ALLA RICONOSCENZA

Giovanni Volpato (Angarano, circa 1735-Roma 1803) fu un importante incisore e ceramista, operante a Roma. Il venticinquenne Antonio Canova (Possagno 1757-Roma 1822), grazie a lui, ottenne la commissione del grandioso monumento sepolcrale di papa Clemente XIV per la chiesa dei Santi Apostoli a Roma, cui lavorò tra il 1783 e il 1787, ponendo le basi della scultura neoclassica.

Ciò spiega la stima, amicizia e riconoscenza che Canova nutrì nei confronti di Volpato, cui volle innalzare, a testimonianza di ciò, nel porticato della stessa chiesa, questo monumento: AMICO OPTIMO MNEMOSYNON / DE ARTE SUA POSUIT

Crâne d'Opossum de Virginie / Virginia opossum Skull (Didelphis virginiana)

fr.wikipedia.org/wiki/Didelphis_virginiana

 

Condylobasal length : 12,5 cm

Zygomatic width : 6,7 cm

(Incisors are from composite specimens.)

 

I: 5/4; C: 1/1; Pm: 3/3; M: 4/4 = 50

 

Masupial skull characteres:

- possibly more than 3 incisors by half jaw

- possibly 4 molars (3 maximum in placental mammals)

- palatal holes

- nasal enlarged at its base, close to frontal bones

- inflection of the mandibular angular process

- jugal participating in the jaw articulation in the mandibular fossa

- ear bulla absent ?

 

Classe : Mammalia, Metatheria (=Marsupialia)

Ordre : Didelphimorphia

Famille : Didelphidae

Genre : Didelphis