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!

 

Commentary.

 

Cliffs over 200 feet surround this stack-laden

section of Watergate Bay.

At low tide vast expanses of golden beach are exposed.

The surf along this stretch of North Cornwall is world-renowned and nearby Fistral Beach, in Newquay, is its mecca.

The grandeur of the cliffs is enhanced by their geology.

The largely dark colours of Mid-Devonian slates, at almost 400 million years old, make up most of the cliffs and stacks.

North to south the stacks are named Queen Bess,

Samaritan Island, Red Cove Island, Pendarves Island

and Carnewas Island.

They appear as sharp, incisor, dog-teeth diminishing in height from north to south.

So much of this Northern Coast is awesome in its scale and grandeur, it is hard not to be moved by its mystique, myth, legend and magic.

It is truly one of the finest stretches of coastline I have ever seen!

 

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.

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

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

 

Sagui

Callitrichinae (também chamada Hapalinae) é uma subfamília de Macacos do Novo Mundo, da família Cebidae. Popularmente, são conhecidos por saguis, soim ou sauim, apesar de que para o gênero Leontopithecus, é mais comum o termo mico-leão.

 

Sagui-de-tufos-pretos

 

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.

 

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.

Highest Explore Position #83 ~ On July 27th 2008.

 

Timber Wolf Cub - Colchester Zoo, Colchester, Essex, England - Saturday July 21st 2008.

Click here to see the Larger image

 

Baby Wolf Cub - Born May 20th 2008.

 

Yup...another point n shoot effort taken through the glass at distance...what could have been if I had, had my Canon and the Sigma long lens hey....:O(((

Oh well...as they say......

 

The gray wolf or grey wolf (Canis lupus), also known as the timber wolf or wolf, is a mammal of the order Carnivora. The gray wolf is the largest wild member of the Canidae family and an ice age survivor originating during the Late Pleistocene around 300,000 years ago. DNA sequencing and genetic drift studies indicate that the gray wolf shares a common ancestry with the domestic dog, (Canis lupus familiaris) and might be its ancestor. A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion. Gray wolves are typically apex predators in the ecosystems they occupy. Gray wolves are highly adaptable and have thrived in temperate forests, deserts, mountains, tundra, taiga, grasslands and urban areas.

 

Though once abundant over much of North America and Eurasia, the gray wolf inhabits a very small portion of its former range because of widespread destruction of its habitat, human encroachment of its habitat, and the resulting human-wolf encounters that sparked broad extirpation. Considered as a whole, however, the gray wolf is regarded as being of least concern for extinction according to the International Union for the Conservation of Nature and Natural Resources. Today, wolves are protected in some areas, hunted for sport in others, or may be subject to extermination as perceived threats to livestock and pets.

 

In areas where human cultures and wolves are sympatric, wolves frequently feature in the folklore and mythology of those cultures, both positively and negatively.

 

Physical characteristics

Wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule. In general, height varies from 0.6 to .95 meters (26–38 inches) at the shoulder and weight ranges from 20 (44 lb.) up to 68 (150 lb.) kilograms, which together make the gray wolf the largest of all wild canids. Although rarely encountered, extreme specimens of more than 77 kg (170 lb.) have been recorded in Alaska, Canada and Russia. The heaviest recorded wild wolf in the New World was killed on 70 Mile River in east central Alaska on July 12, 1939 and weighed 79 kg (175 lb.), while the heaviest recorded wild wolf in the Old World was killed after WWII in the kobelyakski Area of the Poltavskij Region in the Russian SFSR and weighed 86 kg (189 lb.). The smallest wolves come from the Arabian Wolf subspecies, the females of which may weigh as little as 10 kg (22 lb) at maturity. Wolves are sexually dimorphic, with females in any given wolf population typically weighing 20% less than males. They also have narrower muzzles and foreheads, slightly shorter, smoother furred legs and less massive shoulders. Wolves can measure anywhere from 1.3 to 2 meters (4.5–6.5 feet) from nose to the tip of the tail, which itself accounts for approximately one quarter of overall body length.

 

Wolves are built for stamina, possessing features ideal for long-distance travel. Their narrow chests and powerful backs and legs facilitate efficient locomotion. They are capable of covering several miles trotting at about a pace of 10 km/h (6 mph), and have been known to reach speeds approaching 65 km/h (40 mph) during a chase. One emale wolf was recorded to have made 7 metre bounds when chasing prey.

 

Wolf paws are able to tread easily on a wide variety of terrains, especially snow. There is a slight webbing between each toe, which allows them to move over snow more easily than comparatively hampered prey. Wolves are digitigrade, which, with the relative largeness of their feet, helps them to distribute their weight well on snowy surfaces. The front paws are larger than the hind paws, and have a fifth digit, the dewclaw, that is absent on hind paws. Bristled hairs and blunt claws enhance grip on slippery surfaces, and special blood vessels keep paw pads from freezing. Scent glands located between a wolf's toes leave trace chemical markers behind, helping the wolf to effectively navigate over large expanses while concurrently keeping others informed of its whereabouts. Unlike dogs and coyotes, wolves lack sweat glands on their paw pads. This trait is also present in Eastern Canadian Coyotes which have been shown to have recent wolf ancestry. Wolves in Israel are unique due to the middle two toes of their paws being fused, a trait originally thought to be unique to the African Wild Dog.

Wolves molt in late spring or early summer.Wolves have bulky coats consisting of two layers. The first layer is made up of tough guard hairs that repel water and dirt. The second is a dense, water-resistant undercoat that insulates. The undercoat is shed in the form of large tufts of fur in late spring or early summer (with yearly variations). A wolf will often rub against objects such as rocks and branches to encourage the loose fur to fall out. The undercoat is usually gray regardless of the outer coat's appearance. Wolves have distinct winter and summer pelages that alternate in spring and autumn. Females tend to keep their winter coats further into the spring than males. North American wolves typically have longer, silkier fur than their Eurasian counterparts.

Fur coloration varies greatly, running from gray to gray-brown, all the way through the canine spectrum of white, red, brown, and black. These colors tend to mix in many populations to form predominantly blended individuals, though it is not uncommon for an individual or an entire population to be entirely one color (usually all black or all white). A multicolor coat characteristically lacks any clear pattern other than it tends to be lighter on the animal's underside. Fur color sometimes corresponds with a given wolf population's environment; for example, all-white wolves are much more common in areas with perennial snow cover. Aging wolves acquire a grayish tint in their coats. It is often thought that the coloration of the wolf's pelage serves as a functional form of camouflage. This may not be entirely correct, as some scientists have concluded that the blended colors have more to do with emphasizing certain gestures during interaction.

At birth, wolf pups tend to have darker fur and blue irises that will change to a yellow-gold or orange color when the pups are between 8 and 16 weeks old. Though extremely unusual, it is possible for an adult wolf to retain its blue-colored irises.

Adolescent wolf with golden-yellow eyes.Wolves' long, powerful muzzles help distinguish them from other canids, particularly coyotes and golden jackals, which have more narrow, pointed muzzles. Wolves differ from domestic dogs in a more varied nature. Anatomically, wolves have smaller orbital angles than dogs (>53 degrees for dogs compared with <45 degrees for wolves) and a comparatively larger brain capacity. Larger paw size, yellow eyes, longer legs, and bigger teeth further distinguish adult wolves from other canids, especially dogs. Also, precaudal glands at the base of the tail are present in wolves but not in dogs.

 

Wolves and most larger dogs share identical dentition. The maxilla has six incisors, two canines, eight premolars, and four molars. The mandible has six incisors, two canines, eight premolars, and six molars. The fourth upper premolars and first lower molars constitute the carnassial teeth, which are essential tools for shearing flesh. The long canine teeth are also important, in that they hold and subdue the prey. Capable of delivering up to 10,000 kPa (1450 lbf/in²) of pressure, a wolf's teeth are its main weapons as well as its primary tools. The dentition of grey wolves is better suited to bone crushing than those of other modern canids, though it is not as specialised as that found in hyenas.

 

Wolf saliva has been shown to reduce bacterial infection in wounds and accelerate tissue regeneration.

Serp Iwashi footsteps were unaturally loud as a certain resonance is held within the tunnels mouth. No pulse running through that skin..no warmth..his movements almost casual if not for the obvious hinderance of such an overbearing sculpture of steel and wires..Stepping nearer as he hovered above the woman..The faintest seism of his weight almost bending the street to his will as those jaws remained clenched above.Lowly hissing slipping through as that immense palm would move to rest atop the right shoulder..a greeting..an acknowledgement..

 

Ashur Kentoku follows Anna's gaze and smiles at the two kittens.

 

Jason Rae looks to Shadowkat with teary eyes, didnt know what point she was making, and keeps crying

 

Ashur Kentoku quickly whips her face toward the tall black figure and narrows her eyes. She watches warily, flexing her clawed fingers....

 

Rogue Tuqiri blinks, the low growls still rolling up and tumbling through her vocal chords as she watched the thing... man... whatever it was, approach. All the hair that dusted her velvety skin was raised, a fear rolling through as she couldn't identify what it he was. Frightened eyes darted to Anna, and she shuddered.

 

Anna Newall feels Serp's hand on her shoulder. Her baser instincts scream out for her to scoop Chan up and run. If her mind were clearer, she would probably listen to that instinct. In her current enraged state, she stands her ground. She imagines that she is channeling Serp's imposing presence through her contact with him. In her mind's eye, her eyes have even begun to glow red as she stares at Chan. "Serp... if you don't mind, I will have to talk to you later. I have an important family matter to attend to here. Chan, I can accept that you really forgot not to ride your scooter... but why did you lie to me about it on the phone? You said you didn't know where it was when it was RIGHt under you."

 

Channel Liberty whimpers, staring up at her mother and Serp faceing her almost as one person, she falls back completely on her tail as she backs against the wall, "ah..ah got mixed up! ah tol'ju ah weres settin' on it after! ah din't mean t' Lie Mumma!!"

 

Channel Liberty brings one hand up protectively as she pushes back against the wall, tears forming in her eyes as she stares upward at them in sheer frightened terror

 

Serp Iwashi would resist the temptation to draw an index finger aside his temple in some scratching motion..Disregarding wishes was all too enjoyable with razored ends clawing into the slope of the shoulder region..No verbal remarks..no quips..just holding her there..A prism of that hatred unlocked and rushing through that touch as he would continue to squeeze and squeeze..Who was she to speak to him in such a manner..His eyes locking over the child..watching the expression that he knew would follow and nearly tasting it as the squirming would likely ensue.

 

Ashur Kentoku keeps watching the tall dark figure...she remembers past encounters with it and stands ready in case it decided to...misbehave.

 

Jason Rae says in a low tone "I hidings from da ememies"

 

Anna Newall feels a blossom of searing pain blooming outward from her shoulder as Serp begins to damage flesh and connective tissue. She can hear her bones creaking under the strain. Fighting to maintain a steely mask, she can't conceal a slight quiver in her lip and the hot glaze of tears forming over her eyes. She takes a deep breath to steady her voice. Sensing that she has made a dire mistake by ignoring her instinct to run, she does the next best thing. "Go home, Chan. Go to the Center with your scooter. Do not stop anywhere until you get there. Don't leave the Center for any reason unless Dani or I gets you. Do you understand?"

 

Channel Liberty nods mutely, still staring upward fearfully at both of them

 

Jason Rae says in a whispers "Da tewworist that attacked my's book"

 

Serana Aridian watches still, trying to figure out what is going on

 

Anna Newall struggles to control her tone as Chan sits motionless instead of doing as she's told. "Go, Chan!" Anna feels her voice cracking as she says the only thing she wants Chan to remember, if this should be the last time they speak. "I love you, Chan. Go home, and be good for Dani. I love you."

 

Rogue Tuqiri looks up at the Serp, at the mamma kitty, then at Chan. Very slowly, she leans over, nosing the kitten's ear to spur her along.

 

Fern Sabre wonders if she should just walk by or stay and help. She see's Anna is hurt and can hear a strain in her voice. She looks at the others wondering why no one is doing anything.

 

Channel Liberty slowly moves at first, then turns and crawlls as fast as possible on all fours, until she's at the end of the tunnel where she breaks into an all out run!

 

Serp Iwashi stayed silent for a few passing seconds..The abscence of the lips largely masking his expressions yet the sadistic bliss gleamed through tainted ink..Some ebon plague running the course of those patches pulling into a smirk..The tremors of laughter stirring within his hull as he lowers his head down beside Anna's left ear.."How many -children - do you have miss..newall..." Shearing quality to his mechanical vocals lingering for some time as it would invade the fleshy interior of her means of hearing..The grip unfalteringas his massive frame held close to her backside..The weight comming down and a chill through not fear perhaps but the physical contact from eduded frost like sheathes of plates rubbing against the flimsy cast of her garb.

 

Ashur Kentoku steps foward as she realizes the dark figure is hurting Anna and extends her claws, whipping one hand up to the dark creature's throat area to rest the diamond-hard, razor-sharp claws against it..."Release her and step back," she purrs. "Now. Or I will decapitate you, and I doubt you could function well without a head." Her tone is quiet but clear, her pale eyes dance with fire...

 

Rogue Tuqiri chuffs, watching the tiny ne leave, then bristled a little more and panted her feet behind her, eyeing the dark and fear-inspiring apparition that was waking pain in Anna's shoulder like a nightmare. She spat a hiss in it's direction, the heart beat in her chest pounding wildly in her ribs. She slinks back into the wall, bumping the forgotten scooter, ears laid back, eyes darting to either end of the street.

 

Anna Newall stares at the wall in front of her and gives Serp a vague answer, as though from very far away. "Wherever there is need, I find children. I am mother to the poor, the tired, the huddled masses. If I should meet my end here today, I shall only regret that I did not touch more souls." Anna looks to her left and then to her right, though it hurts to move her neck. "You should all go. I love you for your show of concern, but what happens here will happen whether you intervene or not."

 

Ashur Kentoku shakes her head..."I've fought and driven off this creature before, and it had help the last time. I'll do better this time." She keeps her eyes trained on the red orbs and speaks to Serp..."This is not a matter for discussion. If you do not release her within seconds, I will carry out my threat." She tenses as her enhanced reflexes hum and the world seems to slow down around her....

 

Serp Iwashi held a certain composure with feline claws drawn like daggers about the thick gullet..It seemed to hold a ponderosity to the thickness with those skull adorned features contorting to meet the brazen cat..Single eye gravitating to meet the indignation within the face of one he had met before. Without the momenentum he doubted she could carry through such a strike..perhaps a more pez despenser like end to the nefarious one..Anna's words well absorbed for further thought..Full attention drawn to Ashur.." You failed before..and you will - fail- again..."Crackling of each digit peels away from the flesh and matted cloth now soaked under his grip..Almost clinging as he releases to let Anna tumble forward..His head slowly risen back to resume his full stature..though wary of this one..not the typical neko by any means..

 

Jason Rae nods to her "I goes home nows"

 

Ashur Kentoku smiles..."Your memory must be damaged, because I did not fail to stop you from kidnapping one of the Pride back then, and I have succeeded in securing the release of Anna now." She keeps her clawed hand gripping the creature's throat and says, "Anna. Go. Get help for yourself. Serp and I will finish our conversation here."

 

Rogue Tuqiri bounds forward, purring comfortingly to Anna, and decided that if she understood the way humans interacted, she'd do somethign appropriate. As it was, she found herself in a perverted urreal place, save that the blood she scented on Anna was real, and the fear that stammered her set her adrenaline ablaze.

 

Anna Newall feels a sweet throbbing of residual pain and a rush of endorphins as Serp releases her. Her pulse is racing, and though she knows she will be in pain for days, she feels more alive in this moment than she has in a very long time. Her right knee threatens to buckle and betray her, but she shifts more weight on to her metal left leg, the fearless, cold, lifeless artificial limb that never trembles, never cries, never complains... despite the abuse she has heaped upon it. She is shaken out of her stupor by Ashur's words, and she says the only words that she can force her lips to form. "Thank you."

 

Anna Newall sees Chan approaching and is spurred into action. She starts to lift her right arm to point, but she is quickly reminded that her right side isn't functional right now. She points with her left hand instead. "Home, Chan!"

 

Channel Liberty comes running back down the ramp and stops short as she stares at Serp and Anna

 

Channel Liberty looks up at Anna, "ah wen' an' got help..." she replies so quietly she can barely be heard

 

Eamon Cale draws his guns smoothly. Holding one behing his back, he steps in front of Chan, eyes darting over the scene before them.

 

Elise Capalini eyes Ash and Serp--and leaves them be. Tonight is not her night to be fucking around with nasty tempered mechs. "Chan, Anna, out of here now," she says in a low growl.

 

Serp Iwashi stygian form seemed to ooze an unseen black tar through ones skin..The penetration was enough to plant the seeds of corruption inside he flesh..Abstract maggots boiling under the skin like each one of the children she wished to save..Her body some vessel of protection now pierced..A web of deciet and lies that ran deep within midians roots that only he could so masturfully tame..An awakening as the most devious grin was birthed out of the shadows of his features..Clicking marks shifting his jaws rotation with metal on metal grazing one another through unnaturally large incisors..shearing measures to rend the flesh right off that frame..An air of sarcasm dribbling out through such lazy mannerisms as elongated digits wriggle about below..Descended vision taking note that the claws were still there..The rolling of machinery through the copious depth of his neck..Teeth gnashing down in a clangerous bite..though amusement roiled in each strike..chattering.." Why not continue this at another location..

 

Serp Iwashi or do you wish to be broken in front of the mob..."Crimson pools englightened in a glow over that malleable texture of flesh he knew so well..furr or not..all the same..like pale moon light consumed by demonic energies to givr a tinge to her skin.. The deep resonance within his unfathomed tone overshadowing all other sounds if even for a moment.

 

Anna Newall looks at the people that Chan has brought to render aid. She isn't accustomed to running away and leaving others to fight in her stead, but she finds that she has no other choice. She has a child to think of, and she's not the young lady she used to be. Silently, but with a nod to each of those present, she begins walking toward the MCMC with a sense of purpose, pausing only to snag Chan's arm and pull her along. She tries not to think about the priest, the philanthropist, and the friend that she has left behind with the monster.

 

Elise Capalini looks at Auntie and Eamon. "Ash can handle him," she says softly.

 

Ashur Kentoku waits until she hears Anna and the kittens have moved away, then slowly releases her clawed hand from the dark creature's throat, letting it slide down the chest before giving a firm shove, showing some strength for her small frame, the motion pushing her and the figure another pace part. "Oh, here is just fine," she purrs. "I don't mind where you get your come-uppance, if thats' what you want." She stands ready, clawed hands flexing and ready to rend and tear, her lips in a gentle smile....

 

Eamon Cale half-turns his head, watching as Anna leaves with her daughter. His gaze flicks to Elise, at her quiet words, but he doesn't leave just yet. Torn between his nature and what looks like a lass who knows what she's doing, he scowls at Serp and Ash. "We can't just fecking -leave- her..."

 

Elise Capalini watches Anna and Chan go, only partially relieved. Her mind is on Laz and Bianca; she knows that Eamon is right--God will be with both of them this night, but still. "Eamon, I need you," she says in a low, firm tone at his shoulder. "I need your help with Bianca. Ash," she calls down, "we can't stay--I have cats in trouble."

 

Ashur Kentoku: "Then tend to them," she mews, without looking back, watching the dark figure before her. She focuses her attention on the figure before her...

 

Serp Iwashi let out some odd mechanized wail..Ethereal in the ghostly quality held to the one known as the shadow warden..Something so refreshing as he basked in the challenge presented before him..Hissing pops of dense machinery rolling his cranium about..Chest plates perked out momenentarily as he suckled in a great breath..as if to steal some of that precious air..to pick up on all the little tastes that could be carried in through such scents..Cybernetic orbs swirling about as the smoothness of that supple skin would tease him.." You may strike at will..."There was no fancy stances..no battle formation of sorts..to stand there merely talle and coldly evil..Cold lenses falling down the trail of her bare flesh..Rugged chin dipped slightly as a demented tilt accompanied that fixation..The rumbling of that stentorian tone frightfully blunt in its display with illusions of fear nothing more then that..His heel driven further into the cracks now spreading outward under his bulk..

 

Catabolis Plutonian turns, a red flush still evident on his cheeks. HIs eyes widen at the scene behind him, then narrow into tiny slits. He could spot the one called "Ash" and Elise in the distance, and a whole host of strangers.

 

Eamon Cale exhales. He can't argue that. And neither can he argue that the lass facing off against Serp looks neither worried or ready to back down. He swears again under his breath, but nods grimly and holsters his guns. St. Michael would be getting a bloody workout tonight. "Right, let's go," he rasps, and turns away, starting up the street.

 

Ashur Kentoku: ...and says, "Unlike you, I do not relish inflicting pain for the joy of it. I am, however, very good at doing the same in order to protect myself and my friends. As previous experience with me should have taught you. And so, unless *you* wish to strike, I suggest that we go our separate ways." Her voice is, as always, quiet but clear, her eyes still filled with that pale fire, staring into the dark figure's red orbs, unflinching...

 

Serp Iwashi diabolical glimpse would be taken within that flimsy cast of flesh..already condeming the woman..Ruby consistancy shimmering through his sight as he canted his head region down..Palms inched behind his backside..Perhaps a bow of some sort to allow the combat to ensue upon such a gesture..Ghastly set of incisors clenching tighter as that cackle that had haunted the streets countless times before now slipps through the cracks..of such a grin..A vast fiery pit waiting to be unleashed as if his exterior was a molten cast.." Very well.." His only utterance as he held his height as leverage against her..LIke hellfire fallen from the heavans those eyes dramatically bolster with renewed presense..nearly blaring against those lighter tones like a scarlet beacon..Shrieking of obsidian blades emerging from his backside as the tails of his coat flail behind the movement..Deceptively slow in movement but coiled with enough of that savored energy now released as the entire form shifts off to her right..Knees drawn dow

 

Serp Iwashi drawn down to lower his own stance as whirling blades try to embrace her from the backside in the last hug she would likely ever recieve if full successful..Violence begeting more of the same..something he drank in large quanties alongside the last squelched cries drawn into that void..

 

Ashur Kentoku sees the movements begin, fast but not fast enough, her heightened reflexes and central nervous system humming with energy...she pounces gracefully into the air, leaping upward and allowing the blades to sweep by below her and, at the apex of her evasive leap, she snaps a leg out at the creature's face, her booted foot striking like a maddened snake...her feline heritage allows her powerful leaps to the safety of the rootfops, and powerful attacks if she chooses to use that power in such a manner as now.

 

Serp Iwashi felt the rush of air through a gust now blowing aside ebon folds about the layers of that leathery containment. The boot squarely planting itself along the side of the titanium sheath that held the virtually only vital organ that still existed within the abomination.. Vibration spreading through the construct with a snapping sound forcing a region of his neck exposed..yet there was no grunt..no painfully voiced expression..Steel like determination only rivaled by the very carapace he adorned..Left palm slamming into the asphalt with a blade clattering off to the distance yet his right remained true with a flick of it held downward trying to catch that infamous Achilles tenon running along the same means of her attack..

 

Ashur Kentoku snaps a clawed hand down in a blurred arc to intercept the strike aimed at her legs, the claws digging in and hopefully doing some damage...she uses the kinetic energy from Serp's strike and her parry to twist and roll in mid-air, her body sliding past his as she descended to the ground to land in a crouch to the side and slightly behind him...

 

Serp Iwashi rabid emotions that would bring an ordinary being to that adreneline seem entirely unnessecary through such a nearly insurmountable shell..Nails trying to dig in almost feathering accross the bulk of his forearm trying to rend the alloys away from its master.Torn bits raked away though largely still in perfect harmony with the rest of his form.That smile..a cracked image in some twisted reflection of her inner desires to rend him apart as the blade retracts..the tip held low..His left palm relieving the pavement of that burden and slipping within his coak as a wary eye is cast from the corner of crimson spheres..

 

Ashur Kentoku uses her advantageous position to strike hard and fast, a double claw strike aimed at the arm with the blade....designed to pierce and rupture even strong armour, they hiss through the air, seeking...

 

Serp Iwashi shadowy siloulette shadow seemed to part ways away from its creator as crimson glare heightens..Fiery embers purged from the charred peelings of his constuction as those claws sought to pierce him. Fine spindles unravel about his left palm during near enevitability of the attack hitting its mark yet that arm would quickly rise to let them dip under it..Exposed wrists calling for the hooks ends to tie it together..Black peelings littering the pavement below with thick mechanical digits trying to work about those slender wrists.

 

Ashur Kentoku carries her strike through into a twist and pivot of her body as the arm jus barely escapes her claws, and she spins in place, the dark figure's questing digits going astray. As she spins, she lashes out with a booted foot from her semi-crouched position, the whiplash-fast attack aimed at the back of the figure's knees, in order to knock it down...

 

Serp Iwashi grappling talons of his hook clatter over the pavement again as one knee buckles he would remain there and simply fling the rustic tool right beside her face..Likely merging with those silky strands and arriving out the other end as he would pull back the moment it passed her to hopefully catch her and rip her back within his grip ..A switch off from one hand to the other as the opposing palm held that blade waiting to carve her to his desires.

 

Ashur Kentoku bends aside as the hook flashes at her face, again her reflexes up to the task, and brings her hands up to grasp the cable attached to it, swinging the hook around and over her head then toward Serp, aiming its course to wrap the cable around him and possibly dig in as it was meant to dig, thus giving her the space she wanted to jump away...

 

Serp Iwashi ducks in much the same fashion though lacking the feline grace in a more jerk of his facial construct..A rather feigned gruntish mark of his agitation as the cord is looped about his biceps..now overing the expanse of his chest in some constriction..His position changed as his heels kick up small bits of rubble to tower over her though still entangled in his own means of capturing the crafty cat..Narrowing his vision to reduce his sight to slits of cardinal..Growing irritation fueling him as she jumped well out of distance.

 

Ashur Kentoku leaps onto the nearby rooftop and turns to face the darkness below..."I'll always be here, creature, " she hisses. "Always, and I'll stop you at every turn." She smiles again, and leaps away into the shadows that she too, loves, perhaps at least as much as he did.

 

Serp Iwashi orbs rolled over once with his chest heaving..plates expanding about the pectoral region and biceps alike..His own chord offering little resistance as the cable snaps with a final breath to loosely fall below those heels..Tubular protrusions funneling out his aggravation in beckoned fumes as he sneered..

 

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.

  

Common Two-banded Sea Bream (Diplodus vulgaris) is a species of marine ray-finned fish belonging to the family Sparidae, which includes the seabreams and porgies. This species is found in the north-eastern Atlantic Ocean and the Mediterranean. It is an important species for fisheries and is grown in aquaculture.

 

Diplodus vulgaris has an oval shaped, deep, compressed body with a moderately fleshy-lipped slightly protrusible mouth. There are 8 slender brown coloured incisor-like teeth at the front of each jaw with between 3 and 5 rows of molar-like teeth in the upper jaw and between2 and 4 rows of similar teeth in the lower jaw. The molar like teeth sit behind the incisor like teeth and extend along the sides of each jaw. The dorsal fin is supported by 11 or 12 spines and between 13 and 16 soft rays while there are 3 spines and 12 to 15 soft rays supporting the anal fin. The overall colour is grey, greenish or brownish, paler on the lower body. There is a dark band on the nape which extends to the base of the pectoral fins and to the rear edge of the gill cover, a second dark band rings the caudal peduncle immediately behind the rearmost soft rays of the dorsal and anal fins. This may be less extensive in young individuals. There is a black spot at the base of the pectoral fn. The forked caudal fin is dark, darkening towards the rear margin while the other fins are greyish, also darkening towards their margins. The common two-banded seabream has a maximum published total length of 45 cm (18 in), although 22 cm (8.7 in) is more typical, with a maximum published weight of 1.3 kg (2.9 lb).

 

Diplodus vulgaris is found in the northeastern Atlantic Ocean from the Canary Islands and Madeira north to the Bay of Biscay and throughout the Mediterranean and Black Sea.[9] In the Bay of Biscay the species has been spreading north and is now found as far north as the Channel Islands and Normandy. The common two-banded seabream is an oceanodromous, euryhaline, benthopelagic fish found at depths between 0 and 160 m (0 and 525 ft), although typically found in water less than 50 m (160 ft) deep, over rocky and sandy substrates. The young fishes may be found living among seagrass beds.

 

Diplodus vulgaris is carnivorous, a study of their diet in the Adriatic Sea found that the preyed on crustaceans, molluscs, polychaetes, fish eggs and sea urchins with the most important prey being zooplanktonic copepods and gastropods. They also found that prey preferences changed as the fish grew with smaller fish mainly feeding on zooplankton and larger fish on benthic invertebrates.[11] Another study, off southwestern Portugal, found that the common two-banded seabream preyed on brittle stars, polychaetes, amphipods and sea urchins.[12]

 

The common two-banded seabream is a protandric hermaphrodite. A study in the Gulf of Gabes in Tunisia found that the sex ratio was 1.66 females to each male. It also found that the spawning season ran from October to February, peaking in December and January. The total length at which half of the population attained sexual maturity was around 14.14 cm (5.57 in) for females and 13.57 cm (5.34 in) for males. In the Aegean Sea workers found that the spawning season ran from September until March and peaked during December and that the size that 50% of the population reached sexual maturity was 18.35 cm (7.22 in) for males and 20.37 cm (8.02 in) for females. Females were found to have oocyte counts between 10,727 and 316,730, with a mean of around 73,000.

 

Photo by Nick Dobbs, White Tower Bay, Malta 16-08-2025

Civica Raccolta d'Arte e Raccolta degli incisori marchigiani

Sassoferrato (AN)

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.

  

Sunda Colugo (Galeopterus variegatus). The Sunda or Malayan Colugo is the most widespread of the genus Galeopterus; it occurs in parts of southern Myanmar and southern Thailand, localised areas of Laos, Cambodia and Vietnam, and has an extensive range in Peninsular Malaysia, Singapore and Sumatra where suitable forest still exists.

 

A divergent lineage of Galeopterus occurs in Java (Janečka et al, 2008), which some consider as a separate species, and the island of Borneo supports the widely-recognised Bornean Colugo Galeopterus borneanus. Mason (2016) concluded that there may actually be 6 species of Galeopterus.

 

Colugos have large eyes with excellent night vision, small ears and a pointed snout. Some of its teeth are unusual, for example the lower incisors point outwards and are comb-like in structure.

 

Their diet includes leaves and young shoots. During the day colugos rest mainly on tree trunks, generally high up, but sometimes just three metres or so from the ground; they may also make use of tree holes. At dusk they become active, gliding from tree to tree to feed.

 

Females carry a single young (rarely twins) which clings underneath; when roosting, the young often poke their head out from beneath the female. In flight, the young are carried clinging to the flight membrane. Males are smaller than females.

 

The Sunda Colugo is generally mottled grey or greenish-grey but many individuals are reddish to yellowish-orange; males are predominantly reddish.

 

Colugos are rarely heard vocalising; Lim (2007) describes calls from sparring Sunda Colugo males as "a cracking or ripping sound, like the ripping of a thick piece of cardboard".

 

In Singapore this species has proven itself to be adaptable to fragmented forests in semi-urban settings; it makes use of tree plantings next to major roads and other linear plantings to navigate between fragments of habitat. It has been observed gliding across 6-lane highways, if the median divider supports mature trees.

 

Photo by Nick Dobbs, Berjaya Resort, Langkawi 23-12-2023

Skull of spotted hyaena from Mikumi, Tanzania. The hyaena's toolkit includes incisors for nibbling, large canines for stabbing and tearing, massive premolars for crushing bones, and scissor-like 'carnassial' molars that can shear elephant hide.

Highest Explore Position #187 ~ On March11th 2009.

 

Baby African Elephant - Howlettes Wildlife Park, Kent, England - Sunday March 9th 2009.

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Well as promised here's the smallest lil Ellie I've ever seen...you can tell how small he is compared to the tyre he's rubbing up against..:O)

They must get on very well at the park, because there were about 5 baby Elephants there...although this one was the smallest...:O)

They have loads of room to roam about and lots of trees to eat, so perhaps that's why they are so happy..:O))

 

Anyhoo...I hope you are all having an awesome Tuesday..:O))

  

From Wikipedia, the free encyclopedia ~ African elephants are the species of elephants in the genus Loxodonta, one of the two existing genera in Elephantidae. Although it is commonly believed that the genus was named by Georges Cuvier in 1825, Cuvier spelled it Loxodonte. An anonymous author romanized the spelling to Loxodonta and the ICZN recognizes this as the proper authority.

Fossil Loxodonta have only been found in Africa, where they developed in the middle Pliocene.

 

Size ~ African elephants are bigger than Asian Elephants. Males stand 3.64 meters (12 ft) tall at the shoulder and weigh 5,455 kg (12,000 lbs), while females stand 3 meters (10 ft) and weigh 3,636 kg to 4,545 kg (8,000 to 11,000 lbs). However, males can get as big as 15,000 lbs (6,800 kg).

 

Teeth ~ Elephants have four molars; each weighs about 11 lb (5.0 kg) and measures about 12 inches long. As the front pair wear down and drop out in pieces, the back pair shift forward and two new molars emerge in the back of the mouth. Elephants replace their teeth six times. At about 40 to 60 years of age the elephant no longer has teeth and will likely die of starvation, a common cause of death.

Their tusks are teeth; the second set of incisors become the tusks. They are used for digging for roots and stripping the bark off trees for food, for fighting each other during mating season, and for defending themselves against predators. The tusks weigh from 50-100 pounds and can be from 5 to 8 feet (2.4 m) long. Unlike Asian elephants, both bulls and cows have tusks. The enamel plates of the molars are lesser in number than in Asian elephants.

 

Species ~ Loxodonta adaurora, extinct, presumed antecedent of the modern African elephants.

African Bush Elephant (Loxodonta africana).

 

African Forest Elephant (Loxodonta cyclotis). ~ Bush and Forest Elephants were formerly considered subspecies of the same species Loxodonta africana. However, they are nowadays generally considered to be two distinct species. The African Forest Elephant has a longer and narrower mandible, rounder ears, a different number of toenails, straighter and downward tusks, and considerably smaller size. With regard to the number of toenails: the African Bush Elephant normally has 4 toenails on the front foot and 3 on the hind feet, the African Forest Elephant normally has 5 toenails on the front foot and 4 on the hind foot (like the Asian elephant), but hybrids between the two species commonly occur.

 

Conservation ~ Men with African elephant tusks, Dar es Salaam, c. 1900Poaching significantly reduced the population of Loxodonta in certain regions during the 20th century. An example of this poaching pressure is in the eastern region of Chad—elephant herds there were substantial as recently as 1970, with an estimated population of 400,000; however, by 2006 the number had dwindled to about 10,000. The African elephant nominally has governmental protection, but poaching is still a serious issue.

Human encroachment into or adjacent to natural areas where bush elephants occur has led to recent research into methods of safely driving groups of elephants away from humans, including the discovery that playback of the recorded sounds of angry honey bees are remarkably effective at prompting elephants to flee an area. Some elephant communities have grown so large, in Africa, that some communities have resorted to culling large amounts to help sustain the ecosystem.

Highest Explore Position #457 ~ On March 31st 2009.

New Position now ~ #322 ~ On April 1st 2009.

 

Ring Tailed Lemurs & Baby Lemur - Wingham Wildlife Park, Kent, England - Sunday March 29th 2009.

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Well, firstly, for those interested...My Sky Satellite system is now fixed..YAHHH..:)))

The last 5 days have been like the dark ages..lol..I think it's the first time I've used a "Manual" tv guide...that's one from the paper to you..lol...in years...I've got soooooooo used to using the "i" button on my remote...I almost forgot what it was like to scan the TV pages...from a selection of FIVE!!!!...Channels..:)

 

Anyhoo.....back to the image...yesterday I was back at Wingham Wildlife Park in Kent, England...and in amongst the Lemurs again...once again I had some on my head..lol

However...since I was last there, it looks like some of them have been busy..because a couple of them now have lil babies....although, you wouldn't want to be this baby, unless you were a bit of a thrill seeker, because Mummy Lemur spent most of the time jumping and climbing up and down the ropes and wooden structures, with this lil chap clinging on for grim death...how he/she didn't fall off is beyond me...he/she must have a very good grip..that's all I can say..:))

I've got loads of shots of this lil guy...but I won't bore you with them all, you will be pleased to hear..lol

The weather was sunny and cold yesterday with blue sky's and a bit of cloudage (That's not a word, I know, but I invented it...so it is now..lol)...so twas a good day's photography all round....now I just have to wade through the hundreds of images I took...a man's work is never done hey..lol

 

Okey dokey...I hope you are all having a great start to the working week...:)

 

From Wikipedia, the free encyclopedia ~ The Ring-tailed Lemur (Lemur catta) is a large Strepsirhine primate and the most recognized lemur due to its long, black and white ringed tail. It belongs to Lemuridae, one of four lemur families. It is the only member of the Lemur genus. Like all lemurs it is endemic to the island of Madagascar. Known locally as Hira (Malagasy) or Maki (French and Malagasy), it inhabits gallery forests to spiny scrub in the southern regions of the island. It is omnivorous and the most terrestrial of lemurs. The animal is diurnal, being active exclusively in daylight hours.

The Ring-tailed Lemur is highly social, living in groups of up to 30 individuals. It is also matriarchal, a trait common among lemurs but uncommon among other primates. To keep warm and reaffirm social bonds groups will huddle together forming a lemur ball. The Ring-tailed Lemur will also sunbathe, sitting upright facing its underside, with its thinner white fur towards the sun. Like other lemurs, this species relies strongly on its sense of smell and marks its territory with scent glands. The males perform a unique scent marking behavior called spur marking and will participate in stink fights by impregnating their tail with their scent and wafting it at opponents.

As one of the most vocal primates, the Ring-tailed Lemur utilizes numerous vocalizations including group cohesion and alarm calls. Despite the lack of a large brain (relative to Simiiform primates) experiments have shown that the Ring-tailed Lemur can organize sequences, understand basic arithmetic operations and preferentially select tools based on functional qualities.

Despite being listed as Near Threatened by the IUCN Red List and suffering from habitat destruction, the Ring-tailed Lemur reproduces readily in captivity and is the most populous lemur in zoos worldwide, numbering more than 2000 individuals. It typically lives 16 to 19 years in the wild and 27 years in captivity.

 

Anatomy and physiology ~ An adult Ring-tailed Lemur may reach a body length between 39 and 46 cm (15 and 18 in) and a weight between 2.3 and 3.5 kg (5.1 and 7.7 lb). The species has a slender frame and narrow face, reminiscent of a vulpine muzzle. Like all lemurs, its hind limbs are longer than its forelimbs. Females have two pairs of mammary glands, but only one pair is functional.

Furless scent glands are present on both males and females. Both genders have apocrine and sebaceous glands in their genital regions, as well as antebrachial glands located on the inner surface of the forearm in proximity of the wrist. However, only the male has a horny spur that overlays this scent gland. The males also have brachial glands on the axillary surface of their shoulders.

The Ring-tailed Lemur's trademark, a long, bushy tail, is ringed in alternating black and white transverse stripes, numbering Thirteen to Fifthteen each for both colors, and always ending in a black tip. Its tail is longer than its body, measuring up to 64 cm (25.2 in) in length. The tail is not prehensile and is only used for balance, communication, and group cohesion.

The pelage, or fur, is dense. The ventral (chest) coat and throat are white or cream, and the dorsal (back) coat is gray to rosy-brown. The crown is dark gray, while the ears and cheeks are white. The muzzle is dark grayish and the nose is black, and the eyes are encompassed by black lozenge-shaped patches.

The black skin is visible on the nose, genitalia, and the palms and soles of the limbs. The Ring-tailed Lemur shares several adaptations with other lemurs. Its fingers are slender, padded, and semi-dexterous with flat, human-like nails. It grooms orally by licking and tooth-scraping with narrow, procumbent lower incisors and canines, called a toothcomb. Lastly, it has a toilet-claw (sometimes referred to as a grooming claw) on the second toe of each hind limb specialized for personal grooming, specifically to rake through fur that is unreachable by the mouth and toothcomb.

The species' eyes can be a bright yellow or orange. Unlike most diurnal primates, but like all strepsirhine primates, the Ring-tailed Lemur has a tapetum lucidum, or reflective layer behind the retina of the eye, that enhances night vision.

Done in Ai, Finalized in Photoshop.

 

This is Naelith the Hollowmother, a Wraithkin born not of death — but of grief left unresolved. Her form is a cruel echo of beauty: skeletal limbs stretched too thin, veiled in a cursed gothic corset wrought from bone and sorrow. Her face is stripped of humanity, a rictus grin filled with grotesquely oversized human incisors, locked in a silent scream that never ends. Her glowing eyes burn not with life, but with remembrance weaponized.

 

Naelith drifts through the cursed ruins of Gravehollow, drawing power from forgotten names and broken oaths. The air grows still where she walks. Memory twists. Those who hear her scream never truly forget — even if they no longer remember what they’ve lost.

 

“They tried to unwrite her. But she remains — every scream you never dared to make.”

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

 

Sony alpha-300 DSLR, with ~10s exposure using a small LED flash light to illuminate areas selectively.

 

Camels are very cool animals. You'll notice the fangs at the front of the mouth (on the right) that males use for fighting. These fangs are actually modified incisors and the smaller posterior fangs are the actual canines. The other upper incisors are lost in maturity and the upper palate resembles more advanced artiodactyls such as bovids with a toothless upper snout and a bottum jaw filled with large shovel like incisors anteriorly (these aren't visible in this photo). The back molars are rather larger and selenodont (meaning moon-teeth, which refers to the cresent shapes that increase surface area for their wash-board like chewing) as seen in most ungulates.

 

Despite the similarities in dentition with some of the more advanced artiodactyls (the ontogenic reduction of upper incisors and selenodont molars), camels, along with llamas and kin, belong to the suborder Tylopoda, which is the most basal group of extant artiodactyls. This means that pigs, peccaries, hippos, whales, and dolphins are all more closely related to cows, goats and antelopes than camels and other camelids are. If you're not familiar, pigs, peccaries, and hippos have prominent incisors and canines throughout life and molars/premolars that look more like a human than a deer or cow. Thus, tylopods actually do not represent a gradation to the ultimate derived artiodactyl form, they're actually a completely independent lineage that, through convergent evolution, ended up looking like modern artiodactyls in their dental structure. It helps to understand that camelids (along with horses) evolved in North America and were relatively isolated from the Old World, where artiodactyls began their diversification. Thus, camelids and equids became something like the equivalent of bovids and cervids in North America until landmasses moved around and the taxonomic groups became thoroughly mixed across the globe.

 

Last note: you may notice the enamel chipping away on the teeth of this specimen, and that is what happens when you bleach a skull too thoroughly. Wasn't me though.

Crâne de Chat domestique / Domestic Cat Skull (Felis catus)

 

Adult female

This one is special because of its dentition. Only 1 canine and 3 incisors are left in the front part (1 molar and 1 premolar broken otherwise). The alveolus of the "missing" teeth are all closed and cured which means it lost its teeth at least a couple months before death.

 

I think this is maybe because of fight, because I guess front teeth are the most exposed when bitting and when being hit by an other cat plus premolars and molars are not worn down at all so it's not because of food.

This was one of the first images I took in this area; the reverse progression of fangs seems subconscious in hindsight.

The koala (Phascolarctos cinereus), sometimes called the koala bear, is an arboreal herbivorous marsupial native to Australia. It is the only extant representative of the family Phascolarctidae and its closest living relatives are the wombats. The koala is found in coastal areas of the mainland's eastern and southern regions, inhabiting Queensland, New South Wales, Victoria, and South Australia. It is easily recognisable by its stout, tailless body and large head with round, fluffy ears and large, dark nose. The koala has a body length of 60–85 cm (24–33 in) and weighs 4–15 kg (9–33 lb). Fur colour ranges from silver grey to chocolate brown. Koalas from the northern populations are typically smaller and lighter in colour than their counterparts further south. These populations possibly are separate subspecies, but this is disputed.

 

Koalas typically inhabit open Eucalyptus woodland, as the leaves of these trees make up most of their diet. This eucalypt diet has low nutritional and caloric content and contains toxic compounds that deter most other mammals from feeding on it. Koalas are largely sedentary and sleep up to twenty hours a day. They are asocial animals, and bonding exists only between mothers and dependent offspring. Adult males communicate with loud bellows that intimidate rivals and attract mates. Males mark their presence with secretions from scent glands located on their chests. Being marsupials, koalas give birth to underdeveloped young that crawl into their mothers' pouches, where they stay for the first six to seven months of their lives. These young koalas, known as joeys, are fully weaned around a year old. Koalas have few natural predators and parasites, but are threatened by various pathogens, such as Chlamydiaceae bacteria and koala retrovirus.

 

Because of their distinctive appearance, koalas, along with kangaroos and emus, are recognised worldwide as symbols of Australia. They were hunted by Indigenous Australians and depicted in myths and cave art for millennia. The first recorded encounter between a European and a koala was in 1798, and an image of the animal was published in 1810 by naturalist George Perry. Botanist Robert Brown wrote the first detailed scientific description of the koala in 1814, although his work remained unpublished for 180 years. Popular artist John Gould illustrated and described the koala, introducing the species to the general British public. Further details about the animal's biology were revealed in the 19th century by several English scientists. Koalas are listed as a vulnerable species by the International Union for Conservation of Nature. Among the many threats to their existence are habitat destruction caused by agriculture, urbanisation, droughts, and associated bushfires, some related to climate change. In February 2022, the koala was officially listed as endangered in the Australian Capital Territory, New South Wales, and Queensland.

 

Etymology

The word "koala" comes from the Dharug gula, meaning 'no water'. Although the vowel "u" was originally written in the English orthography as "oo" (in spellings such as coola or koolah — two syllables), the spelling later became "oa" and the word is now pronounced in three syllables, possibly in error.

 

Adopted by white settlers, "koala" became one of several hundred Aboriginal loan words in Australian English, where it was also commonly referred to as "native bear", later "koala bear", for its supposed resemblance to a bear. It is also one of several Aboriginal words that made it into International English alongside words like "didgeridoo" and "kangaroo". The generic name, Phascolarctos, is derived from the Greek words φάσκωλος (phaskolos) 'pouch' and ἄρκτος (arktos) 'bear'. The specific name, cinereus, is Latin for 'ash coloured'.

 

Taxonomy

The koala was given its generic name Phascolarctos in 1816 by French zoologist Henri Marie Ducrotay de Blainville, who would not give it a specific name until further review. In 1819, German zoologist Georg August Goldfuss gave it the binomial Lipurus cinereus. Because Phascolarctos was published first, according to the International Code of Zoological Nomenclature, it has priority as the official name of the genus. French naturalist Anselme Gaëtan Desmarest coined the name Phascolarctos fuscus in 1820, suggesting that the brown-coloured versions were a different species than the grey ones. Other names suggested by European authors included Marodactylus cinereus by Goldfuss in 1820, P. flindersii by René Primevère Lesson in 1827, and P. koala by John Edward Gray in 1827.

 

Evolution

The koala is classified with wombats (family Vombatidae) and several extinct families (including marsupial tapirs, marsupial lions and giant wombats) in the suborder Vombatiformes within the order Diprotodontia. The Vombatiformes are a sister group to a clade that includes macropods (kangaroos and wallabies) and possums. The koala's lineage possibly branched off around 40 million years ago during the Eocene.

 

The modern koala is the only extant member of Phascolarctidae, a family that includes several extinct genera and species. During the Oligocene and Miocene, koalas lived in rainforests and had more generalised diets. Some species, such as the Riversleigh rainforest koala (Nimiokoala greystanesi) and some species of Perikoala, were around the same size as the modern koala, while others, such as species of Litokoala, were one-half to two-thirds its size Like the modern species, prehistoric koalas had well developed ear structures which suggests that they also made long-distance vocalisations and had a relatively inactive lifestyle. During the Miocene, the Australian continent began drying out, leading to the decline of rainforests and the spread of open Eucalyptus woodlands. The genus Phascolarctos split from Litokoala in the late Miocene, and had several adaptations that allowed it to live on a specialised eucalyptus diet: a shifting of the palate towards the front of the skull; upper teeth lined by thicker bone, molars located relatively low compared the jaw joint and with more chewing surface; smaller pterygoid fossa; and a larger gap separating the incisor teeth and the molars.

 

P. cinereus may have emerged as a dwarf form of the giant koala (P. stirtoni), following the disappearance of several giant animals in the late Pleistocene. A 2008 study questions this hypothesis, noting that P. cinereus and P. stirtoni were sympatric during the middle to late Pleistocene, and the major difference in the morphology of their teeth. The fossil record of the modern koala extends back at least to the middle Pleistocene.

 

Molecular relationship between living Diprotodontia families based on Phillips and collages (2023)

Vombatidae (wombats)

Phascolarctidae (koalas)

Acrobatidae

Tarsipedidae (honey possum)

Petauridae (wrist-winged gliders and allies)

Pseudocheiridae (ringtail possums and allies)

Macropodidae (kangaroos, wallabies and allies)

Phalangeridae (brushtail possums and cuscuses)

Burramyidae (pygmy possums)

 

Morphology tree of Phascolarctidae based on Beck and collages (2020)

Thylacoleonidae (extinct marsupial lion and allies)

Vombatomorphia (wombats and fossil relatives)

Phascolarctidae

Priscakoala lucyturnbullae

Madakoala spp.

Perikoala robustus

Nimiokoala greystanesi

Litokoala dicksmithi

Litokoala kutjamarpensis

Phascolarctos cinereus

  

Genetics and variations

Three subspecies are recognised: the Queensland koala (Phascolarctos cinereus adustus, Thomas 1923), the New South Wales koala (Phascolarctos cinereus cinereus, Goldfuss 1817), and the Victorian koala (Phascolarctos cinereus victor, Troughton 1935). These forms are distinguished by pelage colour and thickness, body size, and skull shape. The Queensland koala is the smallest of the three, with silver or grey short hairs and a shorter skull. The Victorian koala is the largest, with shaggier, brown fur and a wider skull. The geographic limits of these variations are based on state borders, and their status as subspecies is disputed. A 1999 genetic study suggests koalas exist as a cline within a single evolutionarily significant unit with limited gene flow between local populations.

 

Other studies have found that koala populations have high levels of inbreeding and low genetic variation. Such low genetic diversity may have been caused by declines in the population during the late Pleistocene. Rivers and roads have been shown to limit gene flow and contribute to the isolation of southeast Queensland populations. In April 2013, scientists from the Australian Museum and Queensland University of Technology announced they had fully sequenced the koala genome.

 

Characteristics

The koala is a robust animal with a large head and vestigial or non-existent tail. It has a body length of 60–85 cm (24–33 in) and a weight of 4–15 kg (9–33 lb), making it among the largest arboreal marsupials. Koalas from Victoria are twice as heavy as those from Queensland.  The species is sexually dimorphic, with males 50% larger than females. Males are further distinguished from females by their more curved noses and the presence of chest glands, which are visible as bald patches.  The female's pouch opening is secured by a sphincter which holds the young in.

 

The pelage of the koala is denser on the back. The back fur colour varies from light grey to chocolate brown.  The belly fur is whitish; on the rump it is mottled whitish and dark. The koala has the most effective insulating back fur of any marsupial and is highly resilient to wind and rain, while the belly fur can reflect solar radiation. The koala's curved, sharp claws are well adapted for climbing trees. The large forepaws have two opposable digits (the first and second, which are opposable to the other three) that allow them to grip small branches. On the hind paws, the second and third digits are fused, a typical condition for members of the Diprotodontia, and the attached claws (which are still separate) function like a comb.  The animal has a robust skeleton and a short, muscular upper body with relatively long upper limbs that contribute to its ability to scale trees. In addition, the thigh muscles are anchored further down the shinbone, increasing its climbing power. 

 

For a mammal, the koala has a proportionally small brain,  being 60% smaller than that of a typical diprotodont, weighing only 19.2 g (0.68 oz) on average. The brain's surface is fairly smooth and "primitive".  It does not entirely fill up the cranial cavity, unlike in most mammals,  and is lightened by large amounts of cerebrospinal fluid. It is possible that the fluid protects the brain when animal falls from a tree.  The koala's small brain size may be an adaptation to the energy restrictions imposed by its diet, which is insufficient to sustain a larger brain. Because of its small brain, the koala has a limited ability to perform complex, unusual behaviours. For example, it will not eat plucked leaves on a flat surface, which conflicts with its normal feeding routine.

 

The koala has a broad, dark nose with a good sense of smell, and it is known to sniff the oils of individual branchlets to assess their edibility.  Its relatively small eyes are unusual among marsupials in that the pupils have vertical slits, an adaptation to living on a more vertical plane. Its round ears provide it with good hearing,  and it has a well-developed middle ear. The koala larynx is located relatively low in the vocal tract and can be pulled down even further. They also possess unique folds in the velum (soft palate), known as velar vocal folds, in addition to the typical vocal folds of the larynx. These features allow the koala to produce deeper sounds than would otherwise be possible for their size.

 

The koala has several adaptations for its poor, toxic and fibrous diet.  The animal's dentition consists of the incisors and cheek teeth (a single premolar and four molars on each jaw), which are separated by a large gap (a characteristic feature of herbivorous mammals). The koala bites a leaf with the incisors and clips it with the premolars at the petiole, before chewing it to pieces with the cusped molars.  Koalas may also store food in their cheek pouches before it is ready to be chewed. The partially worn molars of koalas in their prime are optimal for breaking the leaves into small particles, resulting in more efficient stomach digestion and nutrient absorption in the small intestine,  which digests the eucalyptus leaves to provide most of the animal's energy.  A koala sometimes regurgitates the food into the mouth to be chewed a second time.

 

Koalas are hindgut fermenters, and their digestive retention can last for up to 100 hours in the wild or up to 200 hours in captivity. This is made possible by their caecum—200 cm (80 in) long and 10 cm (4 in) in diameter—possibly the largest for an animal when accounting for its size.  Koalas can hold food particles for longer fermentation if needed. They are more likely keep smaller particles as larger ones take longer to digest.  While the hindgut is relatively large, only 10% of the animal's energy is obtained from digestion in this chamber. The koala's metabolic rate is only 50% of the typical mammalian rate, owing to its low energy intake,  although this can vary between seasons and sexes.  They can digest the toxic plant secondary metabolites, phenolic compounds and terpenes present in eucalyptus leaves due to their production of cytochrome P450, which breaks down these poisons in the liver. The koala replaces lost water at a lower rate than some other species like some possums.  It maintains water by absorbing it in the caecum, resulting in drier faecal pellets packed with undigested fibre. 

 

Distribution and habitat

The koala's geographic range covers roughly 1,000,000 km2 (390,000 sq mi), and 30 ecoregions. It ranges throughout mainland eastern and southeastern Australia, including the states of Queensland, New South Wales, Victoria, and South Australia. The koala was also introduced to several nearby islands. The population on Magnetic Island represents the northern limit of its range.

 

Fossil evidence shows that the koala's range stretched as far west as southwestern Western Australia during the late Pleistocene. They were likely driven to extinction in these areas by environmental changes and hunting by Indigenous Australians.  Koalas were introduced to Western Australia at Yanchep in 2022. Koalas can be found in both tropical and temperate habitats ranging from dense woodlands to more spaced-out forests. In semi-arid climates, they prefer riparian habitats, where nearby streams and creeks provide refuge during times of drought and extreme heat.

 

Behaviour and ecology

Koalas are herbivorous, and while most of their diet consists of eucalypt leaves, they can be found in trees of other genera, such as Acacia, Allocasuarina, Callitris, Leptospermum, and Melaleuca. Though the foliage of over 600 species of Eucalyptus is available, the koala shows a strong preference for around 30. They prefer plant matter with higher protein over fibre and lignin.  The most favoured species are Eucalyptus microcorys, E. tereticornis, and E. camaldulensis, which, on average, make up more than 20% of their diet. Despite its reputation as a picky eater, the koala is more generalist than some other marsupial species, such as the greater glider. The koala does not need to drink often as it can get enough water in the eucalypt leaves,  though larger males may additionally drink water found on the ground or in tree hollows.  When feeding, a koala reaches out to grab leaves with one forepaw while the other paws hang on to the branch. Depending on the size of the individual, a koala can walk to the end of a branch or must stay near the base.  Each day, koalas eat up to 400 grams (14 oz) of leaves, spread over four to six feeding periods.  Despite their adaptations to a low-energy lifestyle, they have meagre fat reserves and need to feed often. 

 

Due to their low-energy diet, koalas limit their activity and sleep 20 hours a day. They are predominantly active at night and spend most of their waking hours foraging. They typically eat and sleep in the same tree, possibly for as long as a day.  On warm days, a koala may rest with its back against a branch or lie down with its limbs dangling.  When it gets very hot, the koala rests lower in the canopy and near the trunk, where the surface is cooler than the surrounding air. It curls up when it gets cold and wet.  A koala will find a lower, thicker branch on which to rest when it gets windy. While it spends most of the time in the tree, the animal descends to the ground to move to another tree, leaping along. The koala usually grooms itself with its hind paws, with their double claws, but sometimes uses its forepaws or mouth. 

 

Social life

Koalas are asocial animals and spend just 15 minutes a day on social behaviours. Where there are more koalas and fewer trees, home ranges are smaller and more clumped while the reverse is true for areas with fewer animals and more trees.  Koala society appears to consist of "residents" and "transients", the former being mostly adult females and the latter males. Resident males appear to be territorial and dominant. The territories of dominant males are found near breeding females, while younger males must wait until they reach full size to challenge for breeding rights.  Adult males occasionally venture outside their home ranges; when they do so, dominant ones retain their status.  As a male climbs a new tree, he rubs his chest against it and sometimes dribbles urine. This scent-marking behaviour probably serves as communication, and individuals are known to sniff the bottom of a newly found tree. Chest gland secretions are complex chemical mixtures — about 40 compounds were identified in one analysis — that vary in composition and concentration with the season and the age of the individual.

 

Adult males communicate with loud bellows — "a long series of deep, snoring inhalations and belching exhalations". Because of their low frequency, these bellows can travel far through the forest.  Koalas may bellow at any time of the year, particularly during the breeding season, when it serves to attract females and possibly intimidate other males. They also bellow to advertise their presence to their neighbours when they climb a different tree.  These sounds signal the male's actual body size, as well as exaggerate it; females pay more attention to bellows that originate from larger males. Female koalas bellow, though more softly, in addition to making snarls, wails, and screams. These calls are produced when in distress and when making defensive threats. Squeaking and sqawking are produced when distraught; the former is made by younger animals and the latter by older ones. When another individual climbs over it, a koala makes a low closed-mouth grunt. Koalas also communicate with facial expressions. When snarling, wailing, or squawking, the animal curls the upper lip and points its ears forward. Screaming koalas pull their lips and ears back. Females form an oval shape with their lips when annoyed.

 

Agonistic behaviour typically consists of quarrels between individuals that are trying to pass each other in the tree. This occasionally involves biting. Strangers may wrestle, chase, and bite each other. In extreme situations, a male may try to displace a smaller rival from a tree, chasing, cornering and biting it. Once the individual is driven away, the victor bellows and marks the tree.  Pregnant and lactating females are particularly aggressive and attack individuals that come too close. In general, however, koalas tend to avoid fighting due to energy costs. 

 

Reproduction and development

A young joey, preserved at Port Macquarie Koala Hospital

Koalas are seasonal breeders, and give birth from October to May. Females in oestrus lean their heads back and shake their bodies. Despite these obvious signals, males will try to copulate with any female during this period, mounting them from behind. Because of his much larger size, a male can overpower a female. A female may scream and vigorously fight off her suitors but will accede to one that is dominant or familiar. The commotion can attract other males to the scene, obliging the incumbent to delay mating and fight off the intruders. A female may learn who is more dominant during these fights. Older males usually have accumulated scratches, scars, and cuts on the exposed parts of their noses and their eyelids.

 

Koalas are induced ovulators. The gestation period lasts 33–35 days, and a female gives birth to one joey (although twins do occur). As marsupials, the young are born tiny and barely formed, weighing no more than 0.5 g (0.02 oz). However, their lips, forelimbs, and shoulders are relatively advanced, and they can breathe, defecate and urinate. The joey crawls into its mother's pouch to continue the rest of its development. Female koalas do not clean their pouches, an unusual trait among marsupials.

 

The joey latches on to one of the female's two teats and suckles it.  The female lactates for as long as a year to make up for her low energy production. Unlike in other marsupials, koala milk becomes less fatty as the joey grows in the pouch.  After seven weeks, the joey has a proportionally large head, clear edges around its face, more colouration, and a visible pouch (if female) or scrotum (male). At 13 weeks, the joey weighs around 50 g (1.8 oz) and its head is twice as big as before. The eyes begin to open and hair begins to appear. At 26 weeks, the fully furred animal resembles an adult and can look outside the pouch. 

  

Mother with joey on back

At six or seven months of age, the joey weighs 300–500 g (11–18 oz) and fully emerges from the pouch for the first time. It explores its new surroundings cautiously, clutching its mother for support.  Around this time, the mother prepares it for a eucalyptus diet by producing a faecal pap that the joey eats from her cloaca. This pap comes from the cecum, is more liquid than regular faeces, and is filled with bacteria. A nine month old joey has its adult coat colour and weighs 1 kg (2.2 lb). Having permanently left the pouch, it rides on its mother's back for transportation, learning to climb by grasping branches.  Gradually, it becomes more independent from its mother, who becomes pregnant again after a year, and the young is now around 2.5 kg (5.5 lb). Her bond with her previous offspring is permanently severed and she no longer allows it to suckle, but it will stay nearby until it is one-and-a-half to two years old. 

 

Females become sexually mature at about three years of age and can then become pregnant; in comparison, males reach sexual maturity when they are about four years old, although they can experience spermatogenesis as early as two years.  Males do not start marking their scent until they reach sexual maturity, though their chest glands become functional much earlier. Koalas can breed every year if environmental conditions are good, though the long dependence of the young usually leads to year-long gaps in births. 

 

Health and mortality

Koalas may live from 13 to 18 years in the wild. While female koalas usually live this long, males may die sooner because of their more risky lives.  Koalas usually survive falls from trees and can climb back up, but they can get hurt and even die, particularly inexperienced young and fighting males.  Around six years of age, the koala's chewing teeth begin to wear down and their chewing efficiency decreases. Eventually, the cusps disappear completely and the animal will die of starvation. Koalas have few predators. Dingos and large pythons and some birds of prey may take them. Koalas are generally not subject to external parasites, other than ticks around the coast. The mite Sarcoptes scabiei gives koalas mange, while the bacterium Mycobacterium ulcerans skin ulcers, but even these are uncommon. Internal parasites are few and have little effect.  These include the tapeworm Bertiella obesa, commonly found in the intestine, and the nematodes Marsupostrongylus longilarvatus and Durikainema phascolarcti, which are infrequently found in the lungs.[59] In a three-year study of almost 600 koalas taken to the Australia Zoo Wildlife Hospital in Queensland, 73.8% of the animals were infected with parasitic protozoal genus Trypanosoma, the most frequent of which was T. irwini.

 

Koalas can be subject to pathogens such as Chlamydiaceae bacteria,  which can cause keratoconjunctivitis, urinary tract infection, and reproductive tract infection.  Such infections are common on the mainland, but absent in some island populations.  The koala retrovirus (KoRV) may cause koala immune deficiency syndrome (KIDS) which is similar to AIDS in humans. Prevalence of KoRV in koala populations suggests a trend spreading from north to south, where populations go from being completely infected to being partially uninfected.

 

The animals are vulnerable to bushfires due to their slow speed and the flammability of eucalypt trees. The koala instinctively seeks refuge in the higher branches, where it is vulnerable to intense heat and flames. Bushfires also break up the animal's habitat, which isolates them, decreases their numbers and creates genetic bottlenecks. Dehydration and overheating can also prove fatal.  Consequently, the koala is vulnerable to the effects of climate change. Models of climate change in Australia predict warmer and drier climates, suggesting that the koala's range will shrink in the east and south to more mesic habitats.

 

Human relations

The first written reference to the koala was recorded by John Price, servant of John Hunter, the Governor of New South Wales. Price encountered the "cullawine" on 26 January 1798, during an expedition to the Blue Mountains, but his remarks would first be published in Historical Records of Australia, nearly a century later. In 1802, French-born explorer Francis Louis Barrallier encountered the animal when his two Aboriginal guides, returning from a hunt, brought back two koala feet they were intending to eat. Barrallier preserved the appendages and sent them and his notes to Hunter's successor, Philip Gidley King, who forwarded them to Joseph Banks. Similar to Price, Barrallier's notes were not published until 1897.  Reports of the "Koolah" appeared in the Sydney Gazette in late 1803, and helped provide the impetus for King to send the artist John Lewin to paint watercolours of the animal. Lewin painted three pictures, one of which was used as a print in Georges Cuvier's Le Règne Animal (The Animal Kingdom) (1827).

 

Botanist Robert Brown was the first to write a formal scientific description of the koala in 1803, based on a female specimen captured near what is now Mount Kembla in the Illawarra region of New South Wales. Austrian botanical illustrator Ferdinand Bauer drew the animal's skull, throat, feet, and paws. Brown's work remained unpublished and largely unnoticed, however, as his field books and notes remained in his possession until his death, when they were bequeathed to the British Museum (Natural History) in London. They were not identified until 1994, while Bauer's koala watercolours were not published until 1989.  William Paterson, who had befriended Brown and Bauer during their stay in New South Wales, wrote an eyewitness report of his encounters with the animals and this would be the basis for British surgeon Everard Home's anatomical writings on them.  Home, who in 1808 published his report in the journal Philosophical Transactions of the Royal Society, coined the scientific name Didelphis coola. 

 

George Perry would officially publish the first image of the koala in his 1810 natural history work Arcana.  Perry called it the "New Holland Sloth", and his dislike for the koala, evident in his description of the animal, was reflected in the contemporary British attitudes towards Australian animals as strange and primitive the eye is placed like that of the Sloth, very close to the mouth and nose, which gives it a clumsy awkward appearance, and void of elegance in the combination they have little either in their character or appearance to interest the Naturalist or Philosopher. As Nature however provides nothing in vain, we may suppose that even these torpid, senseless creatures are wisely intended to fill up one of the great links of the chain of animated nature.

  

Natural history illustrator John Gould popularised the koala with his 1863 work The Mammals of Australia.

Naturalist and popular artist John Gould illustrated and described the koala in his three-volume work The Mammals of Australia (1845–1863) and introduced the species, as well as other members of Australia's little-known faunal community, to the public. Comparative anatomist Richard Owen, in a series of publications on the physiology and anatomy of Australian mammals, presented a paper on the anatomy of the koala to the Zoological Society of London. In this widely cited publication, he provided an early description of its internal anatomy, and noted its general structural similarity to the wombat.  English naturalist George Robert Waterhouse, curator of the Zoological Society of London, was the first to correctly classify the koala as a marsupial in the 1840s, and compared it to fossil species Diprotodon and Nototherium, which had been discovered just recently.  Similarly, Gerard Krefft, curator of the Australian Museum in Sydney, noted evolutionary mechanisms at work when comparing the koala to fossil marsupials in his 1871 The Mammals of Australia.

 

Britain finally received a living koala in 1881, which was obtained by the Zoological Society of London. As related by prosecutor to the society, William Alexander Forbes, the animal suffered an accidental demise when the heavy lid of a washstand fell on it and it was unable to free itself. Forbes dissected the fresh specimen and wrote about the female reproductive system, the brain, and the liver — parts not previously described by Owen, who had access only to preserved specimens.  Scottish embryologist William Caldwell — well known in scientific circles for determining the reproductive mechanism of the platypus — described the uterine development of the koala in 1884, and used this new information to convincingly map out the evolutionary timeline of the koala and the monotremes. 

 

Main article: Koala emblems and popular culture

The koala is well known worldwide and is a major draw for Australian zoos and wildlife parks. It has been featured in popular culture and as soft toys.  It benefited the Australian tourism industry by over $1 billion in 1998, and this has subsequently grown. Its international popularly rose after World War II, when tourism to Australia increased and the animals were exported to zoos overseas.  In 1997, about 75% of European and Japanese tourists placed the koala at the top of their list of animals to see. According to biologist Stephen Jackson: "If you were to take a straw poll of the animal most closely associated with Australia, it's a fair bet that the koala would come out marginally in front of the kangaroo".  Factors that contribute to the koala's enduring popularity include its teddy bear-like appearance with childlike body proportions.

 

The koala is featured in the Dreamtime stories and mythology of Indigenous Australians. The Tharawal people believed that the animal helped them get to the continent by rowing the boat. Another myth tells of how a tribe killed a koala and used its long intestines to create a bridge for people from other parts of the world.  How the koala lost its tail has been the subject of many tales. In one, a kangaroo cuts it off to punish the koala for its uncouth behaviour.  Tribes in both Queensland and Victoria regarded the koala as a wise animal which gave valuable guidance. Bidjara-speaking people credited the koala for making trees grow in their arid lands.  The animal is also depicted in rock carvings, though less so than some other species.

 

Early European settlers in Australia considered the koala to be a creeping sloth-like animal with a "fierce and menacing look".  At the turn of the 20th century, the koala's reputation took a more positive turn. It appears in Ethel Pedley's 1899 book Dot and the Kangaroo, as the "funny native bear".  Artist Norman Lindsay depicted a more anthropomorphic koala in The Bulletin cartoons, starting in 1904. This character also appeared as Bunyip Bluegum in Lindsay's 1918 book The Magic Pudding. The most well known fictional koala is Blinky Bill. Created by Dorothy Wall in 1933, the character appeared in several books and has been the subject of films, TV series, merchandise, and a 1986 environmental song by John Williamson.  The koala first appeared on an Australian stamp in 1930.

The song "Ode to a Koala Bear" appears on the B-side of the 1983 Paul McCartney/Michael Jackson duet single Say Say Say.  A koala is the main character in Hanna-Barbera's The Kwicky Koala Show and Nippon Animation's Noozles, both of which were animated cartoons of the early 1980s. Food products shaped like the koala include the Caramello Koala chocolate bar and the bite-sized cookie snack Koala's March. Dadswells Bridge in Victoria features a tourist complex shaped like a giant koala  and the Queensland Reds rugby team has a koala as its icon.

 

Koala diplomacy

Several political leaders and members of royal families had their pictures taken with koalas, including Queen Elizabeth II, Prince Harry, Crown Prince Naruhito, Crown Princess Masako, Pope John Paul II, US President Bill Clinton, Soviet premier Mikhail Gorbachev and South African President Nelson Mandela At the 2014 G20 Brisbane summit, hosted by Prime Minister Tony Abbott, many world leaders, including Russian President Vladimir Putin and US President Barack Obama, were photographed holding koalas. The event gave rise to the term "koala diplomacy", which then became the Oxford Word of the Month for December 2016. The term also includes the loan of koalas by the Australian government to overseas zoos in countries such as Singapore and Japan, as a form of "soft power diplomacy", like the "panda diplomacy" practised by China.

 

Main article: Koala conservation

The koala was originally classified as Least Concern on the Red List, and reassessed as Vulnerable in 2014. In the Australian Capital Territory, New South Wales and Queensland, the species was listed under the EPBC Act in February 2022 as endangered by extinction. The described population was determined in 2012 to be "a species for the purposes of the EPBC Act 1999" in Federal legislation.

 

Australian policymakers had declined a 2009 proposal to include the koala in the Environment Protection and Biodiversity Conservation Act 1999. A 2017 WWF report found a 53% decline per generation in Queensland, and a 26% decline in New South Wales. The koala population in South Australia and Victoria appear to be abundant; however, the Australian Koala Foundation (AKF) argued that the exclusion of Victorian populations from protective measures was based on a misconception that the total koala population was 200,000, whereas they believed in 2012 that it was probably less than 100,000. AKF estimated in 2022 that there could be only 43,000–100,000.[80] This is compared with 8 to 10 million at the start of the 20th century. The Australian Government's Threatened Species Scientific Committee estimated that the 2021 koala population was 92,000, down from 185,000 two decades prior.

 

The koala was heavily hunted by European settlers in the early 20th century,  largely for its fur. Australia exported as many as two million pelts by 1924. Koala furs were used to make rugs, coat linings, muffs, and on women's garment trimmings. The first successful efforts at conserving the species were initiated by the establishment of Brisbane's Lone Pine Koala Sanctuary and Sydney's Koala Park Sanctuary in the 1920s and 1930s. The owner of the latter park, Noel Burnet, created the first successful breeding program and earned a reputation as a top expert on the species.

 

One of the biggest anthropogenic threats to the koala is habitat destruction and fragmentation. Near the coast, the main cause of this is urbanisation, while in rural areas, habitat is cleared for agriculture. Its favoured trees are also taken down to be made into wood products.  In 2000, Australia had the fifth highest rate of land clearance globally, having removed 564,800 hectares (1,396,000 acres) of native plants.  The distribution of the koala has shrunk by more than 50% since European arrival, largely due to fragmentation of habitat in Queensland. Nevertheless, koalas live in many protected areas.

 

While urbanisation can pose a threat to koala populations, the animals can survive in urban areas provided enough trees are present. Urban populations have distinct vulnerabilities: collisions with vehicles and attacks by domestic dogs. Cars and dogs kill about 4,000 animals every year. To reduce road deaths, government agencies have been exploring various wildlife crossing options, such as the use of fencing to channel animals toward an underpass, in some cases adding a ledge as a walkway to an existing culvert. Injured koalas are often taken to wildlife hospitals and rehabilitation centres. In a 30-year retrospective study performed at a New South Wales koala rehabilitation centre, trauma was found to be the most frequent cause of admission, followed by symptoms of Chlamydia infection

Stockgrove 11/12/2019 SP91722914

Eastern gray squirrel

From Wikipedia, the free encyclopedia

Conservation status

Least Concern (IUCN 3.1)[2]

Scientific classificationedit

Kingdom:Animalia

Phylum:Chordata

Class:Mammalia

Order:Rodentia

Family:Sciuridae

Genus:Sciurus

Subgenus:Sciurus

Species:S. carolinensis

Binomial name

Sciurus carolinensis

Gmelin, 1788

Subspecies

S. c. carolinensis

S. c. extimus

S. c. fuliginosus

S. c. hypophaeus

S. c. pennsylvanicus

Sciurus carolinensis range map.svg

Range in red

(excludes introduced populations)[clarification needed]

Synonyms

S. pennsylvanica

S. hiemalis

S. leucotis

S. fulginosus

S. migratorius

The eastern gray squirrel (Sciurus carolinensis), also known as the grey squirrel depending on region, is a tree squirrel in the genus Sciurus. It is native to eastern North America, where it is the most prodigious and ecologically essential natural forest regenerator.[3][4] Widely introduced to certain places around the world, the eastern gray squirrel in Europe, in particular, is regarded as an invasive species.

  

Distribution

Sciurus carolinensis is native to the eastern and midwestern United States, and to the southerly portions of the eastern provinces of Canada[clarification needed]. The native range of the eastern gray squirrel overlaps with that of the fox squirrel (Sciurus niger), with which it is sometimes confused, although the core of the fox squirrel's range is slightly more to the west. The eastern gray squirrel is found from New Brunswick, through southwestern Quebec and throughout southern Ontario plus in southern Manitoba, south to East Texas and Florida.[2] Breeding eastern gray squirrels are found in Nova Scotia, but whether this population was introduced or came from natural range expansion is not known.[5] It has also been introduced into Ireland,[6] Britain, Italy, South Africa, and Australia (where it was extirpated by 1973).[2] Eastern gray squirrels in Europe are a concern because they have displaced some of the native squirrels there. In 1966, this squirrel was also introduced to Vancouver Island in Western Canada in the area of Metchosin, and has spread widely from there. They are considered highly invasive and a threat to both the local ecosystem and the native red squirrel.[7]

 

A prolific and adaptable species, the eastern gray squirrel has also been introduced to, and thrives in, several regions of the western United States. The gray squirrel is an invasive species in Britain; it has spread across the country and has largely displaced the native red squirrel, S. vulgaris. In Ireland, the red squirrel has been displaced in several eastern counties, though it still remains common in the south and west of the country.[8] That such a displacement might happen in Italy is of concern, as gray squirrels might spread to other parts of mainland Europe.[9]

 

Etymology

The generic name, Sciurus, is derived from two Greek words, skia, meaning shadow, and oura, meaning tail. This name alludes to the squirrel sitting in the shadow of its tail.[10] The specific epithet, carolinensis, refers to the Carolinas, where the species was first recorded and where the animal is still extremely common. In the United Kingdom and Canada, it is simply referred to as the "grey squirrel". In the US, "eastern" is used to differentiate the species from the western gray squirrel (Sciurus griseus).

 

Description

 

Bounding tracks in concrete

 

Close-up of an eastern gray squirrel's head; note the brownish fur on its face, the gray fur on its back and the white fur on its underside.

 

Melanistic eastern gray squirrel carrying a peanut

The eastern gray squirrel has predominantly gray fur, but it can have a brownish color. It has a usual white underside as compared to the typical brownish-orange underside of the fox squirrel.[11] It has a large bushy tail. Particularly in urban situations where the risk of predation is reduced, both white[12] – and black-colored individuals are quite often found. The melanistic form, which is almost entirely black, is predominant in certain populations and in certain geographic areas, such as in large parts of southeastern Canada. Melanistic squirrels appear to exhibit a higher cold tolerance than the common gray morph; when exposed to -10 °C, black squirrels showed an 18% reduction in heat loss, a 20% reduction in basal metabolic rate, and an 11% increase to non-shivering thermogenesis capacity when compared to the common gray morph.[13] Genetic variations within these include individuals with black tails and black-colored squirrels with white tails. (See tree squirrel for more information on these color variations.)

 

The head and body length is from 23 to 30 cm (9.1 to 11.8 in), the tail from 19 to 25 cm (7.5 to 9.8 in), and the adult weight varies between 400 and 600 g (14 and 21 oz).[14][15] They do not display sexual dimorphism, meaning there is no gender difference in size or coloration.[16]

 

The tracks of an eastern gray squirrel are difficult to distinguish from the related fox squirrel and Abert's squirrel, though the latter's range is almost entirely different from the gray's. Like all squirrels, the eastern gray shows four toes on the front feet and five on the hind feet. The hind foot-pad is often not visible in the track. When bounding or moving at speed, the front foot tracks will be behind the hind foot tracks. The bounding stride can be two to three feet long.[17]

 

The dental formula of the eastern gray squirrel is 1023/1013 (Upper teeth/Lower Teeth).[13]

 

1.0.2.3

1.0.1.3

× 2 = 22 total teeth.

 

Incisors exhibit indeterminate growth, meaning they grow consistently throughout life, and their cheek teeth exhibit brachydont (low-crowned teeth) and bunodont (having tubercles on crowns) structures.[13]

 

Behavior

 

Reaching out for food on a garden bird feeder, this squirrel can rotate its hind feet, allowing it to descend a tree head-first.

Like many members of the family Sciuridae, the eastern gray squirrel is a scatter-hoarder; it hoards food in numerous small caches for later recovery.[2] Some caches are quite temporary, especially those made near the site of a sudden abundance of food which can be retrieved within hours or days for reburial in a more secure site. Others are more permanent and are not retrieved until months later. Each squirrel is estimated to make several thousand caches each season. The squirrels have very accurate spatial memory for the locations of these caches, and use distant and nearby landmarks to retrieve them. Smell is used partly to uncover food caches, and also to find food in other squirrels' caches. Scent can be unreliable when the ground is too dry or covered in snow.[18]

 

Squirrels sometimes use deceptive behavior to prevent other animals from retrieving cached food. They will pretend to bury the object if they feel that they are being watched. They do this by preparing the spot as usual, for instance, digging a hole or widening a crack, miming the placement of the food, while actually concealing it in their mouths, and then covering up the "cache" as if they had deposited the object. They also hide behind vegetation while burying food or hide it high up in trees (if their rival is not arboreal). Such a complex repertoire suggests that the behaviors are not innate, and imply theory of mind thinking.[19][20]

 

The eastern gray squirrel is one of very few mammalian species that can descend a tree head-first. It does this by turning its feet so the claws of its hind paws are backward-pointing and can grip the tree bark.[21][22]

 

Eastern gray squirrels build a type of nest, known as a drey, in the forks of trees, consisting mainly of dry leaves and twigs. The dreys are roughly spherical, about 30~60 cm in diameter and are usually insulated with moss, thistledown, dried grass, and feathers to reduce heat loss.[16] Males and females may share the same nest for short times during the breeding season, and during cold winter spells. Squirrels may share a drey to stay warm. They may also nest in the attic or exterior walls of a house, where they may be regarded as pests, as well as fire hazards due to their habit of gnawing on electrical cables. In addition, squirrels may inhabit a permanent tree den hollowed out in the trunk or a large branch of a tree.[23]

 

Eastern gray squirrels are crepuscular,[15] or more active during the early and late hours of the day, and tend to avoid the heat in the middle of a summer day.[23] They do not hibernate.[24]

 

Predation

Predators include humans, hawks, weasels, raccoons, foxes, domestic and feral cats, snakes, owls, and dogs.[23] In its introduced range in South Africa, it has been preyed on by African harrier-hawks.[25]

 

Reproduction

 

Eastern gray squirrels are born hairless with their eyes closed.

Eastern gray squirrels can breed twice a year, but younger and less experienced mothers normally have a single litter per year in the spring. Depending on forage availability, older and more experienced females may breed again in summer.[26] In a year of abundant food, 36% of females bear two litters, but none will do so in a year of poor food.[27] Their breeding seasons are December to February and May to June, though this is slightly delayed in more northern latitudes.[15][23] The first litter is born in February or March, the second in June or July, though, again, bearing may be advanced or delayed by a few weeks depending on climate, temperature, and forage availability. In any given breeding season, an average of 61 – 66% of females bear young.[27] If a female fails to conceive or loses her young to unusually cold weather or predation, she re-enters estrus and has a later litter. Five days before a female enters estrus, she may attract up to 34 males from up to 500 meters away. Eastern gray squirrels exhibit a form of polygyny, in which the competing males will form a hierarchy of dominance, and the female will mate with multiple males depending on the hierarchy established.[13]

  

Eastern gray squirrel drey

Normally, one to four young are born in each litter, but the largest possible litter size is eight.[27] The gestation period is about 44 days.[27] The young are weaned around 10 weeks, though some may wean up to six weeks later in the wild. They begin to leave the nest after 12 weeks, with autumn born young often wintering with their mother. Only one in four squirrel kits survives to one year of age, with mortality around 55% for the following year. Mortality rates then decrease to around 30% for following years until they increase sharply at eight years of age.[27]

 

Rarely, eastern gray females can enter estrus as early as five and a half months old,[23] but females are not normally fertile until at least one year of age. Their mean age of first estrus is 1.25 years.[27] The presence of a fertile male will induce ovulation in a female going through estrus.[13] Male eastern grays are sexually mature between one and two years of age.[28] Reproductive longevity for females appears to be over 8 years, with 12.5 years documented in North Carolina.[13] These squirrels can live to be 20 years old in captivity, but in the wild live much shorter lives due to predation and the challenges of their habitat. At birth, their life expectancy is 1–2 years, an adult typically can live to be six, with exceptional individuals making it to 12 years.

 

Growth and ontogeny

 

Juvenile eastern gray squirrel developing fur

Newborn gray squirrels weigh 13-18 grams and are entirely hairless and pink, although vibrissae are present at birth. 7–10 days postpartum, the skin begins to darken, just before the juvenile pelage grows in. Lower incisors erupt 19–21 days postpartum, while upper incisors erupt after 4 weeks. Cheek teeth erupt during week 6. Eyes open after 21–42 days, and ears open 3–4 weeks postpartum. Weaning is initiated around 7 weeks postpartum, and is usually finished by week 10, followed by the loss of the juvenile pelage. Full adult body mass is achieved by 8–9 months after birth.[13]

 

Communication

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Calls recorded in Surrey, England

As in most other mammals, communication among eastern gray squirrel individuals involves both vocalizations and posturing. The species has a quite varied repertoire of vocalizations, including a squeak similar to that of a mouse, a low-pitched noise, a chatter, and a raspy "mehr mehr mehr". Other methods of communication include tail-flicking and other gestures, including facial expressions. Tail flicking and the "kuk" or "quaa" call are used to ward off and warn other squirrels about predators, as well as to announce when a predator is leaving the area.[29] Squirrels also make an affectionate coo-purring sound that biologists call the "muk-muk" sound. This is used as a contact sound between a mother and her kits and in adulthood, by the male when he courts the female during mating season.[29]

 

The use of vocal and visual communication has been shown to vary by location, based on elements such as noise pollution and the amount of open space. For instance, populations living in large cities generally rely more on the visual signals, due to the generally louder environment with more areas without much visual restriction. However, in heavily wooded areas, vocal signals are used more often due to the relatively lower noise levels and a dense canopy restricting visual range.[30]

A subspecies of the plains zebra, native to eastern Zambia, east of the Luangwa River, Malawi, southeastern Tanzania and northern Mozambique. Crawshay's zebras can be distinguished from other subspecies of plains zebras in that its lower incisors lack an infundibulum [the funnel-like centre of the tooth that is filled with cementum] and has very narrow stripes compared to other forms of the Plains zebra.

but she made it! Yay!

Male hyraxes lack a scrotum and their testicles are tucked away in the abdominal cavity next to the kidneys – same goes for elephants, manatees and dugongs. Female hyraxes have a pair of teats near their arm pits like elephants but in addition they have four more in their groin area. Like elephants, hyraxes also have tusks growing from their incisor teeth. In other mammalian species, tusks grow from the canines. Another characteristic that hyraxes share with elephants is that they have flattened hoof-like nails on the tips of their toes rather than the curved claws seen on other mammals.

The pygmy marmoset is a tiny monkey native to the western Amazon basin. It is the smallest of all true monkeys and one of the smallest of all primates. Adults have tawny or brownish-gold fur above, with black flecking. The belly is a lighter color, varying from yellowish to cream or white. There is a slight ruff of fur around the head, giving the appearance of a tiny mane – in some languages, the pygmy marmoset is called “tiny lion”. Most primates have flat nails like we do, but marmosets and tamarins, including the pygmy marmoset, have sharp claws on all digits except the big toe. These claws are probably an adaptation that helps these small monkeys cling to bark and other surfaces, since their hands aren’t big enough to reach around any but the smallest branches.

 

Preferred habitat of the pygmy marmoset includes the edges of rivers and their floodplains – areas near rivers that are annually inundated from seasonal rising of the river. They are usually not found in higher elevation interior forests that do not flood annually, although they do seem to be able to colonize human-created forest edges around orchards, field and other clearings.

 

This species is not of conservation concern at the present time. Because they reproduce rapidly, have relatively small space requirements, and are found over a large geographic area, pygmy marmosets are in better shape in the wild than many other South American primate species.

 

Longevity

 

A typical lifespan for pygmy marmosets is about 6 or 7 years. Lifespan in the wild is not well known.

 

Behavior

 

Pygmy marmosets live in small family groups of from 2-9 adults and juveniles, with an additional one or two infants still carried by the adults in some groups. The most common group size is 6-7. Most groups are composed of a breeding pair and offspring from up to several successive litters.

 

In the wild, pygmy marmosets rely heavily on gums and saps (exudates) from trees and vines. They scrape the surface of the tree or vine with their specialized chisel-like lower incisor teeth to create a wound out of which exudates flow. These exudates may be an important source of protein, carbohydrates and calcium. Researchers have identified at least 39 types of trees and 19 different vines that pygmy marmosets utilize in this way. They also eat insects and other arthropods and small quantities of fruits and other plant parts.

 

Each pygmy marmoset group uses an area of forest that is usually about an acre or less in size and which it does not share with other groups. The group relies on several trees and vines within this home range for the exudates that make up a large part of their diet; a single tree may be the principal exudate source. If and when the exudate output from these key sources drops, the group may shift to another area of forest.

 

Pygmy marmosets are diurnal (active during the day) and arboreal.

 

Reproduction

 

Pygmy marmoset gestation period is about 19-20 weeks. Most births are of non-identical twins, but females sometimes give birth to single babies or to triplets. Babies weigh only about half an ounce (15 g) at birth! In the wild, births can occur throughout the year, although they may be seasonally clustered in some areas. Females may produce litters as often as twice a year.

 

The father and older youngsters help with the new infants, doing much of the carrying of the babies until they’re able to travel on their own.

 

SIZE

Total length (head, body and tail combined) is usually 13-14 in (33-36cm). More than half of this is tail, with the head and body only about 5 in (13 cm) long combined.

 

WEIGHT

The pygmy marmoset is the smallest of all monkeys and one of the smallest of all primates. Body weight of wild adults averages only about 4 oz (113 g). Well-fed zoo animals may be a little bit heavier.

 

DIET

In the wild, pygmy marmosets rely heavily on gums and saps (exudates) from trees and vines. These exudates may be an important source of protein, carbohydrates and calcium. Wild pygmy marmosets also eat insects and other arthropods and small quantities of fruits and other plant parts. In the Zoo, we feed our pygmy marmosets a primate chow specially formulated for marmosets and tamarins, along with insects, fresh fruits, and gum arabic, a commercially available exudate from acacia trees.

 

GEOGRAPHIC RANGE

The pygmy marmoset is found in the upper Amazon Basin in western Brazil, eastern Peru, eastern Ecuador, southern Colombia, and northern Bolivia.

www.youtube.com/watch?v=A1V-1xL_JAM

 

Il bambino che non gioca non è un bambino, ma l'adulto che non gioca ha perso per sempre il bambino che ha dentro di sé.

(Pablo Neruda)

 

Forse non tutti sanno che....

 

Inventati attorno al 1760 da John Spilsbury,[1] un cartografo e incisore di Londra, i puzzle originariamente erano realizzati dipingendo il soggetto su una tavola di legno e ritagliandolo successivamente in piccoli pezzi per mezzo di un seghetto. I moderni puzzle vengono realizzati incollando una foto su un supporto di cartone che viene successivamente tagliato per mezzo di una fustella di forma assai complessa. Molto importante la precisione dimensionale con cui vengono realizzati i pezzi, perché talvolta essa è l'unico ausilio per distinguere fra loro due pezzi simili e porli nella corretta collocazione.

 

Per quanto riguarda il numero di pezzi, si va dai puzzle formati da poche decine di pezzi, in genere dedicati ai bambini, ai giganti di parecchie migliaia di pezzi (commercialmente vengono realizzati puzzle fino a circa 18.000 pezzi). Dal 2008, tuttavia, è entrato in commercio il puzzle più grande del mondo "Life" (http://www.worldslargestpuzzle.com/index.html), di dimensioni pari a 4.28m x 1.57m e formato da ben 24000 pezzi. Purtroppo in Italia non si trova in vendita, il suo acquisto è possibile effettuarlo solo via su internet. Da notare che molto spesso il numero di pezzi non è esattamente quello indicato sulla confezione, in quanto non sempre il prodotto fra altezza e larghezza (in numero di pezzi) può dare come risultato il numero tondo indicato sulla confezione. Per esempio un puzzle da 1000 pezzi è in genere composto da 999 (37×27) pezzi.

 

Le dimensioni dipendono, oltre che dal numero di pezzi, anche dalle loro dimensioni: nei puzzle con elevato numero di pezzi, questi vengono realizzati leggermente più piccoli in maniera da limitare le dimensioni dell'immagine risultante. Orientativamente un puzzle da 500 pezzi è grande circa 40×50 cm, uno da 1000 pezzi 50×70 cm, un 2000 pezzi 70×100 cm, un 5000 pezzi 100×150 cm, un 9000 pezzi 140×200 cm, un 18000 pezzi 200×300 cm.

 

Curiosità

In un celebre film comico di Stanlio e Ollio, "Il regalo di nozze" (Me and my Pal, Charles Rogers, 1933) si genera una situazione comica per il fatto che, essendo l'ora del matrimonio di Ollio, Stanlio, che è uno dei due testimoni, si perde a fare un puzzle, e così dietro di lui tutti gli altri invitati.

 

(Wikipedia)

 

Scientific Name: Daubentonia madagascariensis

 

The aye-aye is a tiny monkey species with a long tail found only in Madagascar. Due to its bizarre appearance and unusual feeding habits, it is considered by many to be the strangest primate in the world. The aye-aye is the world’s largest nocturnal primate. Unusual physical characteristics include incisors that are continually growing (unique among primates), extremely large ears, and a middle finger which is skeletal in appearance, and is used by the animal as a primary sensory organ.

 

We do not completely know where it got this unique name. Some researchers think it is named after a French naturalist who showed a sign of exclamation after seeing them. Others hypothesize that the name resembles the Malagasy name "hai hai" or "hay hay", which refers to the animal and is used around the island. Still others suggest that the name derives from "heh heh", which is Malagasy for "I don't know". If correct, then the name might have originated from Malagasy people saying "heh heh" to avoid saying the name of a feared, magical animal.

 

Regardless, the the aye-aye is characterized by its unusual method of finding food: it taps on trees to find grubs, then gnaws holes in the wood using its forward-slanting incisors to create a small hole into which it inserts its narrow middle finger to pull the grubs out.

 

For more information: lemur.duke.edu/discover/meet-the-lemurs/aye-aye/

CDV by Hurlbut, West Greenville, PA

period pencil inscription on back

Mark L. Weastcott

David Minnis

C. N. Failes

Sarah Jane Westcott

Anna L. Failes

 

At first glance this carte de visite appears to be an ordinary photo of a small group of family or friends. Additional research reveals some exciting details as well as a minor mystery. On its face, the photo shows three young men and two women, all in civilian clothing. These people are identified in pencil on the reverse as Mark L. Weastcott (sic), David Minnis, C. N. Failes, Sarah Jane Westcott, and Anna L. Failes. Unfortunately there is no indication which name on the reverse of the photo corresponds to each person of the front. The photo was taken by Hurlbut, in West Greenville, Pennsylvania.

 

A preliminary search of the National Park's online Civil War Soldiers and Sailors Database revealed that all three men served in the Union Army from Pennsylvania: Mark Westcott and David Minnis in the 57th PA, and C. N. Failes in the 141st PA Infantry. Further research showed that Westcott was actually a common misspelled version of Westcoatt's actual name by omitting the "a", and that a typo on the website mistakenly identified Failes' unit as the 141st PA -- it actually was the 140th PA. But I still did not know who on the CDV was who.

 

I found the Westcoatt family in Trumbull County Ohio in 1850, Mercer County Pennsylvania in 1860 and Johnson County Iowa in 1870. The parents were Oliver P and Christiana Westcoatt. The children in the family were, in order of age Mary, Mark, Ann, Ezra, Amanda, John, Ida, Oliver Jr., William and Ambrose. Birth years ranged from about 1842 for Mary down to 1868 for Ambrose. The Minnis family showed up in Mercer County Pennsylvania in 1850, 1860 and 1870. The parents were Samuel and Narcissa Minnis. The children here were, in order, David born in 1844, William, John, Cynthia, James, Clara and Mary born in 1863. I had no such luck for finding census records for Failes or his family until he shows up in the 1880 census as head of his own household.

 

Next, I tried to put a name to a specific face on the photo. Through military records, I discovered that C. N. Failes was Caleb N. Failes and he was born in 1840. Westcoatt was born about 1843 and Minnis in 1844. So Failes was the oldest of the men by 3 or 4 years. That was clue number one. Next I noticed that one of the men appeared to be wearing what looks like a diamond shaped pin with a second circular pin and ribbon below it. This could be a Third Corps badge with a round ID tag hanging below it. Regardless of the nature of the lower pin, the upper one clearly reminds me of the diamond shaped lozenge used by the Third Corps. This was clue number two. Lastly, on close inspection, I could not decide if there was a photographic defect showing up on the cheek of the man on the left, or if the blemish was actually a scar. This was clue number three.

 

A trip to the National Archives in Washington, DC allowed me to pull the military, medical and pension records of all three men. (All three men's military biographies are presented in more detail below.) Here I learned that Failes did not serve in the 141st PA as I had been led to believe, but in the 140th PA instead. The 140th PA was assigned to the 5th Corps for the first few months, and then was transferred to the 2nd Corps. Failes thus did not seem to be a candidate for the man wearing the diamond shaped pin. But the 57th PA was part of the 3rd Corps at the time the other two men enlisted in February 1864. Even though the regiment was soon transferred out of the 3rd Corps, it is reasonable to assume that a new recruit could have been talked into buying an ID pin and corps badge before the transfer was announced. Therefore the man standing at the rear could be either Minnis or Westcoatt. The final piece of the puzzle fell into place when the medical and pension records for Westcoatt revealed that he had indeed been shot in the face, and was left with a rather large scar on his right cheek, matching what appears in the photo of the clean-shaven man seated on the left. Therefore, by process of elimination I have tentatively identified the three men in the photo as Mark Westcoatt seated at left, David Minnis standing in rear with lapel pin, and Caleb Failes, the oldest of the three, wearing a beard and seated in front.

 

The only times when all three men could have been together in West Greenville, Pennsylvania where the photo was taken, would have been either before August 1862 when C. N. Failes enlisted, or after June 1865 when all three men were discharged. At no time during their military service were all three men listed as absent at the same time. The presence of Westcoatt's scar and the Third Corps Badge worn by Minnis places this image in the post war period. The lack of a tax stamp on the reverse of the photo may further indicate that it was taken after August 1866 when the tax was repealed. However there is a faint stain that may be the result of a former tax stamp affixed to the back thus possibly dating this to the period 1864-1866, or it could just be the mark of a stamp on an adjoining CDV while held back to back in an album.

 

While I have an idea who the men in the photo are, I still have no clue as to the women. It is clear from the records than neither woman was a wife of Mark Westcoatt or C. N. Failes. Anna Failes might very well be a sister of C. N. Failes. Indeed, the woman sitting in the center seems to have a bit of a resemblance to the man with the goatee that I suspect is Failes, but so far I have found no census records for the Failes family prior to the Civil War. Sarah Jane Westcott remains a mystery. Her name does not correspond to any of Mark's sisters as listed in the census records for the Wesctoatt family. Although the woman at left bears a striking resemblance to the man sitting in front of her whom I believe is Mark Westcoatt I have not been able to figure out who she is. There is also the possibility that the first and last names of the women were inadvertently switched by whoever wrote the names on the back of the card. In that case, Ann L. could be Anna the sister of Mark L. Westcoatt, and Sarah Jane could be somehow related to C. N. Failes.

 

Military Biographies

 

Caleb N. Failes (1840-1921)

 

Caleb N. Failes was born October 22, 1840 in Mercer County, Pennsylvania. On August 15, 1862 he enlisted at Mercer County for 3 years in Company B, 140th Pennsylvania Volunteer Infantry. This regiment was assigned to the 5th Army Corps until December 1862, at which time it was transferred to the 2nd Army Corps. The new regiment was ordered to join the Army of the Potomac in the field, and reached Aquia Creek, Virginia on December 15, 1862. But Failes failed to make it that far. On December 10, he had been sent from the hospital camp at Seward, Maryland to the U.S. Army General Hospital at York, Pennsylvania suffering from Typhoid Fever. Luckily he recovered enough to be returned to duty on February 11, 1863. His health did not last long, however, and on April 10 he was back in the regimental hospital and for the next two weeks he is listed as variously suffering from diarrhea, bronchitis, pains and rheumatism. Then, on April 21, 1863 he was admitted to the hospital of the 1st Division, 2nd Army Corps, Army of the Potomac near Falmouth, Virginia due to "Continued Fever." From there, on June 14, 1863 he was transferred to Carver U.S. Army General Hospital in Washington, DC and was finally returned to duty on August 8. Thus he missed the early fighting of his regiment at Chancellorsville and Gettysburg.

 

By the fall of 1863 it appears Caleb Failes had finally kicked the sick bug. He was back in the ranks for the advance on the Rappahannock in late 1863 and for the spring campaign in early 1864. The 140th PA fought its way through from the Wilderness to Petersburg. By this time the regiment's effective strength was down to about 150 enlisted men, with companies that once numbered 100 men reduced to little bands of 10 or 12 now clustered around a tattered and powder-grimed stand of colors.

 

In the June 18, 1864 attack on Petersburg Failes was wounded in action when he was felled by a large piece of artillery shell. The metal fragment must have been nearly spent because it bounced off his right shoulder rather than perforate his body. Failes was evacuated from the battlefield, and with nearly 600 other wounded was packed onto the steamer Connecticut to be transferred to the Division Number 1 U.S.A. General Hospital at Annapolis, Maryland where he was admitted on June 20. The wound was diagnosed as a "contusion of the right shoulder caused by a piece of shell" and the medical records indicate that it "Requires no treatment." But in those days before x-rays and MRIs, there may well have been internal bone or ligament damage, because it took a very long time for the injury to heal and for him to regain useful movement and strength in his right arm. On July 3, 1864 Failes was transferred from Division No. 1 Hospital to the General Hospital at Camp Parole, just outside the city of Annapolis, where he remained for some time, still listed as suffering from a gunshot wound of the right shoulder. He was granted a two-week furlough on October 31, 1864, presumably to visit his home, and was readmitted to Camp Parole Hospital from furlough on Nov 14, 1864. He was again granted a furlough on January 6, 1865, this time for 30 days, and "Returned on time" by February 3.

 

The 140th PA had finished out the war at Appomattox Court House and returned to Washington, DC in May 1865. Its members were mustered out of the army at Alexandria, Virginia on May 31. But Caleb Failes was still recuperating in the hospital at Annapolis at that time and missed the regimental discharge. He received his individual muster out at Annapolis on June 8, 1865. Discharged from the service, he returned home to Pennsylvania. About two years later, in 1867 he married Mary C. ("Lottie") Unger and the couple raised several children. Caleb N. Failes died on December 15, 1921 at Warren, Ohio.

 

Mark L. Wesctoatt (~1843-1902) & David A. Minnis (1844-1919)

 

Mark L. Westcoatt was listed as 20 years old and a laborer when he enlisted in Company B, 57th PA Infantry at West Greenville, Mercer County, Pennsylvania, on February 10, 1864. This was the same company in which his father, Oliver P. Westcoatt, had enlisted on October 21, 1861. At the time, the elder Westcoatt had given his occupation as a blacksmith and his age as 44 (one year below maximum military draft age). In the spring of 1862 Oliver was detailed as an ordnance guard. But army life was hard on the older man, and he was given a disability discharge for being "debilitated" while at White's Ford, Maryland, on October 28, 1862. Although only one year had elapsed since Oliver's enlistment, his age as listed in army records had inexplicably advanced from 44 to 51 years old. In early 1864, the veterans of the regiment came home on furlough and apparently took the opportunity to enlist new recruits, and among the new enlistees was Mark Westcoatt. Perhaps the younger man wanted to follow the example of his father, or maybe he felt the need to redeem the family's honor after his father's discharge. Mark Westcoatt was described as six feet tall with dark hair and dark or hazel eyes.

 

David Andrew Minnis was born on September 26, 1844 in Sheakleyville, Mercer County, Pennsylvania. He was 19 and a farmer when he enlisted just two days after Mark Westcoatt in the same company on February 12, 1864. Minnis was described as 5 feet 8 inches tall with gray eyes and light hair. Both men had signed on for a three-year term of enlistment and were mustered into Federal service with the 57th PA Infantry on March 1, 1864. The 57th PA had been part of the 3rd Army Corps up till now, but in March 1864 it was transferred to the 2nd Army Corps.

 

In early March the veterans and new recruits arrived in Virginia in preparation of the spring campaign. The new men would presumably have been given cursory military instruction in an attempt to bring them up to speed with the veterans. It would have been a tough introduction to life in the field for the new men, but within 60 days the regiment would be thrown into the meat grinder of combat at the Wilderness. David Minnis survived the battle unscathed. But in this, his first fight, Mark Westcoatt was seriously wounded. The regimental casualty sheet noted Westcoatt received a gunshot wound of the face on May 5, 1864. He was hit by a .58 caliber minie ball that struck "him in left cheek passing through & knocking out ten of his teeth, the ball coming out at the right side. Said shot fired by the enemy." Had the bullet hit him two inches behind and above, it would have penetrated his temple and killed him instantly.

 

Westcoatt was evacuated from the field and admitted to Stanton U.S. Army General Hospital in Washington, DC, on May 11, 1864. His treatment consisted of a "water dressing" in which the bandages were kept wet in the belief that it promoted healing. He was diagnosed with a gunshot wound to the face with fractured upper jaw. In fact, the front portion of his upper jawbone was completely missing. The bullet "passed latterly through the face carrying away the incisors canine & bicuspid teeth together with the alveolar process of superior maxillary bone. Ball entered left cheek just in front and below malar bone, making its exit at same point in right cheek." Not surprisingly, after blasting its way through his face and carrying away a large chunk of bone and several teeth with it, the bullet tore a much bigger hole on its exit through the right cheek than when it entered on the left side. Westcoatt had "a small round scar (of entrance) upon the left side of face a little posterior to the angle of the mouth: a large stellate scar upon the right side of face into angle of mouth and upward and back 2 1/2 inches and again back and down about the same distance." In all, Westcoatt lost all of his upper teeth "except two molars and the wisdom tooth on the left side and one molar and the wisdom tooth on the right side," either because they and the bone supporting them were directly carried away by the bullet or as a result of being loosened by the shock.

 

After a couple of weeks at Stanton Hospital, Westcoatt was transferred on May 27 to Saterlee U.S. Army General Hospital in West Philadelphia, being admitted there on May 28, 1864. It took six months of convalescence, but Westcoatt, although somewhat impaired in eating and chewing, was returned to duty with his regiment on November 26, 1864.

 

Meanwhile David Minnis survived the brutal fighting in Virginia through the spring and summer of 1864 before the 57th PA settled in for the siege of Petersburg. But life in the trenches was not healthy for other reasons besides enemy bullets. On September 29, 1864 Minnis was admitted to the 3rd Division Depot Field Hospital, 2nd Army Corps, Army of the Potomac due to remittent fever. On October 4, 1864, he was sent on to an army general hospital and arrived at the U.S. Army General Hospital at Beverly, New Jersey on October 7. Two months later, on December 3, 1864, Minnis was transferred to the U.S.A. Gen Hospital at 16th and Filbert Streets in Philadelphia with what was described as "Functional Cardiac Disorder." He too was eventually returned to duty with the 57th PA, arriving back with his regiment on February 8, 1865. The regiment was present at Appomattox Court House on April 9, 1865 when Robert E. Lee surrendered the Confederate Army of Northern Virginia. David Minnis was promoted to corporal on May 1, 1865. And the regiment marched to Washington, DC and did duty at Alexandria until the men were mustered out on June 29, 1865. With the war over, the government no longer needed thousands stands of arms and the former soldiers were allowed to purchase their weapons and take them home with them. David Minnis apparently decided to keep his army issued musket and accouterments in exchange for a $6 stoppage of his pay "for gun and equipment." He returned home to Salem Township, PA and became a boot and shoe maker.

 

Many years after the war, about 1885, David Minnis married Mary Elizabeth Porter who was about 22 years younger than him. In fact she would not even be born until 1867, almost two years after he was discharged from the army. David Minnis died October 4, 1919 at Franklin, Venango County, Pennsylvania. He was 55. His widow lived until 1954.

 

Mark Westcoatt moved to Scott Township, Johnson County, Iowa after the war with his parents and siblings. A few years later, he had moved out of his parent's home and shows up in the 1870 census as a 26 year old farmer living with Caroline Westcott, age 25, and Helen S. Westcott, age 2. However, ten yeas later he appears in the 1880 census at a boarding house in Cedar Township, Benton County, Iowa and is listed as single and a laborer. This raises the question, who were Caroline and Helen, and what happened to them?

 

Mark lived for a time in Mt. Auburn, Barton County, Iowa. The 1885 Iowa state census shows Mark living with his mother and his youngest brother, William Westcoatt, who was about 20 years younger than him.

 

Wescoatt's pension records indicate that he continued to have trouble due to his old wound. After examining him in 1881, a doctor wrote to the Pension Bureau stating, "The teeth of superior maxillary bone are all gone. His face is disfigured and mouth so deformed as to be unable to have a plate and false teeth fitted. Being unable to properly masticate his food for a long time he has now some dyspeptic trouble. While his wound in no way interferes with manual labor I am quite unable to fix the amount of pension which is justly due him. Taking the disfigurement of face and condition of mouth and inability to masticate food or wear false teeth into consideration I believe he is justly entitled to an increase."

 

Over the years, other doctors weighed in as well. "...he incurred gunshot wound of his face which carried away his upper front teeth and the alveolar process so he cannot make artificial teeth do duty. It impairs biting and chewing." 1881

 

"The exit of the missile tore the right upper lip and cheek as shown in the diagram. These scars are normal and cause no disability. We think the disability resulting from the loss of the upper teeth is rated correctly." 1886

 

"That at a result of G.S.W. of upper jaw he is unable to thoroughly and satisfactorily masticate his food and that his digestion is to some extent impaired as a result. That on account of condition of jaw he has been unable to secure a plate that he could wear...in our opinion a satisfactory plate is an impossibility." 1891

 

Pension records also indicate that on August 14, 1893, Mark Westcoatt married Elizabeth R. Kinsie, who at 50 was about three or four years older than him. Notwithstanding the prior census records linking Mark Westcoatt with Caroline Westcott in 1870, his pension records indicate that this was his first marriage. Elizabeth Kinsie, on the other hand, was a widow (her maiden name was Noble) and her 16-year-old son, William Kinsey, lived with them after they were married. Elizabeth died sometime before 1900. Mark Westcoatt passed away on July 24, 1902 in Blackhawk County, Iowa. He was about 58 years old.

 

References:

U.S. Census records for 1850, 1860, 1870, and 1880.

Iowa State Census for 1885

Military, Pension and Medical records United States Archive and Record Administration

Dyer, Frederick H., A Compendium of the War of the Rebellion, Vol. III, Regimental Histories

 

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.

  

These marmosets are gum-feeding specialists. They don't wait for gum-producing trees to exude gum but use their specially adapted chisel-like incisors to make small holes in the bark.This stimulates the flow of gum and enables them to have a year round supply. Their claw-like nails allow them to cling vertically to the trunks as they jump between trees.

 

Information Sourced from Longleat Guidebook.

Silver with gold inlay, 6th century B.C.E.

Diam. 9 cm.

  

This steep-sided hemispherical silver bowl is enlivened with gold appliqué arranged in four registers and with a twenty-two petaled gold-foil rosette covering the base. Beginning with the uppermost register, a frieze of joined lotus flowers and palmettes,1 the motifs depicted on this bowl follow the Achaemenid repertoire very closely. The second register shows fourteen striding composite beasts (one is now lost) with their heads looking backward. The animals, perhaps bull-sphinxes with a single horn, are executed with the characteristic hooked wing, secondary set of wings shown in relief along the sides of their bodies, and stylized musculature seen on such varied Achaemenid objects as cylinder seals, clothing appliqué, and architectural reliefs.2 Twelve double-horned ram-sphinxes circle the next register, while seven striding, snarling lions are depicted below. The lions are the most carefully formed, revealing their incisors within open mouths, manes rendered in regularized rows, and "figure-eight" musculature at their shoulders.

 

The bowl has been hammered from one piece of silver, with beaded-wire borders formed by carving framing the registers. These borders are covered with gold foil, which has been pushed and tooled into position. The gold appliqué, preformed over a matrix and set into spaces carved into the surface of the bowl, originally were fitted below a silver lip. The lip is now lost in most areas due to corrosion of the bowl's silver surface so that the majority of the appliqué are secured with a modern adhesive. The surface has been cleaned extensively and some of the appliqué-all of which appear to be original-have been repaired. Along with many ancient objects from Iran now in the Shumei collection, the bowl bears the nearly invisible stamp of a v within a triangle-probably the mark of a modern collector-located here on the rim.

  

1. See Muscarella 1992, p. 230.

2. For a clearly visible example see Pope and Ackerman 1977, vol. 7, p. 95.

 

Text and image from the website of the Miho Museum.

BIG5. Elephant. Kruger National Park. South Africa. May/2021

 

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

 

Kruger National Park

Kruger National Park is one of the largest game reserves in Africa. It covers an area of around 20,000 square kilometres in the provinces of Limpopo and Mpumalanga in northeastern South Africa, and extends 360 kilometres (220 mi) from north to south and 65 kilometres (40 mi) from east to west.

Source: Wikipedia

Parque Nacional Kruger

O Parque Nacional Kruger é a maior área protegida de fauna bravia da África do Sul, cobrindo cerca de 20 000 km2. Está localizado no nordeste do país, nas províncias de Mpumalanga e Limpopo e tem uma extensão de cerca de 360 km de norte a sul e 65 km de leste a oeste.

Os parques nacionais africanos, nas regiões da savana africana são importantes pelo turismo com safári de observação e fotográfico.

O seu nome foi dado em homenagem a Stephanus Johannes Paul Kruger, último presidente da República Sul-Africana bôere. Foi criado em 31 de Maio de 1926

Fonte: Wikipedia

 

In this image it looks like this pocket gopher has no lips, with the skin from the nose going to the large incisors without lips. Actually the gopher has lips, but they are behind its four enormous incisor teeth, which it uses to keep dirt out of its mouth when digging. An interesting adaptation, perfect for its tunneling way of life.

Botta's pocket gopher (Thomomys bottae) is a pocket gopher native to western North America. It is also known in some areas as valley pocket gopher, particularly here in California. This one was observed in Tehachapi, California in sandy soil adjacent to an agricultural field.

Image - Copyright 2024 Alan Vernon

 

The Toronto Zoo is divided up into seven different geographic regions. Each region showcases animals and plants from that area of the world. They are Indo-Malaya, Afraca,Canadian Domain, Americas. Australasia, Eurasia Wilds, Tundra Trek and Discovery Zone.

The pygmy hippo may resemble a miniature river hippopotamus, but there are structural differences. It is considerably smaller; the head is rounder, proportionately smaller and not so broad and flat. The nostrils are large and almost circular, the eyes are set on the side of the head and do not protrude, the legs are proportionately longer and only the front toes are webbed. As well, the pygmy hippo has only one pair of upper incisors compared to the river hippo’s two pairs. The feet have four toes each with sharp nails. Length of head & body: 1.5 m – 1.8 m, Height to shoulder: 0.8 m, Weight: 160 - 270 kg.

The aye-aye (Daubentonia madagascariensis) is a long-fingered lemur, a strepsirrhine primate native to Madagascar with rodent-like teeth that perpetually grow and a special thin middle finger.

 

It is the world's largest nocturnal primate. It is characterized by its unusual method of finding food: it taps on trees to find grubs, then gnaws holes in the wood using its forward-slanting incisors to create a small hole into which it inserts its narrow middle finger to pull the grubs out. This foraging method is called percussive foraging, and takes up 5–41% of foraging time. From an ecological point of view, the aye-aye fills the niche of a woodpecker, as it is capable of penetrating wood to extract the invertebrates within.

 

The aye-aye is the only extant member of the genus Daubentonia and family Daubentoniidae. It is currently classified as Endangered by the IUCN. (Wikipedia).

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!

 

7463 T Karta Venezia Carta Dell’antica Laguna per l'opera Il Fiore di Venezia Edizione di Tommaso Fontana 1838. Autore della pubblicazione: Ermolao Paoletti padre del pittore Antonio Ermolao Paoletti (1834 – 1912)

 

Titolo: Carta Dell’antica Laguna

Carta non comune della laguna veneta

Tratta da: Il fiore di Venezia, ossia, I quadri, monumenti, vedute e costumi veneziani – Volume 1

Autore della pubblicazione: Ermolao Paoletti padre del pittore Antonio Ermolao Paoletti (1834 – 1912)

Tecnica: acquaforte

Incisore: Berasconi

Editore: Tommaso Fontana – Venezia

Epoca: 1838.

Dimensioni (HxL): 294 mm x 395 mm circa (fogli); 260 mm x 367 mm (stampa)

Bibliografia: Antonio Ermolao Paoletti pp.82 volume 7; Zeno Davoli; La raccolta di stampe Angelo Davoli; Edizioni Diabasis

Villa Cianciafara venne costruita alla fine del Settecento su un preesistente edificio medievale. Filippo Cianciafara, raffinato fotografo e incisore, nacque e visse tra queste mura e in questi giardini, tra puttini, fontane, pergolati, un delizioso tempietto. Condivideva l’amore per l’arte e la natura con i suoi celebri cugini, Giuseppe Tomasi di Lampedusa e Lucio Piccolo. La Villa è uno dei pochi esempi architettonici del XVIII secolo che si presenta pressoché intatto, nonostante calamità naturali e varie vicissitudini. Originariamente, qui si svolgevano soprattutto attività agricole. Dentro, molti preziosi arredi.

 

Foto: il "tempietto" nel giardino.

 

Villa Cianciafara was built at the end of the eighteenth century on a pre-existing medieval building. Filippo Cianciafara, a refined photographer and engraver, was born and lived between these walls and in these gardens, among putti, fountains, pergolas, and a lovely small temple. He shared the love for art and nature with his famous cousins, Giuseppe Tomasi di Lampedusa and Lucio Piccolo. The Villa is one of the few architectural examples of the eighteenth century that appears almost intact despite natural disasters and various vicissitudes. Originally mainly agricultural activities took place here. Many precious furnishings are held inside.

 

Photo: the small "temple" in the garden.

The Pokot (or Pokhot) live in the Baringo district and in the Western Pokot district in Kenya. They are also inhabitants of 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 cattle. A homestead is composed of one or more buildings for a man, his wife and children; the prospective co-wives live in separate houses. Teaching children ethical rules is extremely important. 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, in particular body decoration, are very appreciated among the Pokot. They adorn the body with beads and hairstyling, and proceed to scarifications 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 and advise, usually by the means of animal sacrifices. Their abilities are considered as a divine gift. Clan histories recount the changes of location, through poetry and song, emphasizing the vulnerability of human beings and the importance of supernatural powers that 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 belong to any age-set. After excision, 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 (and not the contrary), often over a period of years. 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.

 

Les Pokot vivent dans le district de Baringo et à l’ouest du district de Pokot au Kenya. Ce sont aussi des habitants de l’Ouganda.Il existe deux principaux sous-groupes selon leur localisation et mode de vie. Le premier groupe est constitué des Pokot des collines qui vivent dans les hautes terres humides dans l’ouest et dans le centre sud, et sont surtout des agriculteurs et pasteurs. Le second groupe est composé des Pokot des plaines qui vivent dans les plaines sèches et infertiles, avec leur bétail. Chaque propriété familiale est composée d’une ou plusieurs bâtiments pour un homme, sa femme et ses femmes, les éventuelles autres épouses vivent dans des maisons séparées. Enseigner aux enfants les règles éthiques est extrêmement important. La plupart des Pokot sont nomades et ont donc interagi avec différents peuples, incorporant leurs coutumes sociales. Les Pokot sont très fiers de leur culture. Les chants, contines, et arts décoratifs, en particulier la décoration du corps, sont particulièrement appréciés chez les Pokot. Ils parent leur corps de perles et coiffures originales, et procèdent à des scarifications et au retrait des incisives centrales inférieures. Les filles Pokot portent un collier de perles fait de tiges d’asparagus. La plupart des Pokot a des connaissances des médicaments à base de plantes, et ils utilisent donc souvent ces traitements avec ceux des hôpitaux. Ils appartiennent aux peuples parlant les langues nilotiques du Kenya.Pour les Pokot, l’univers a deux royaumes : celui d’en haut est le royaume des déités les plus puissantes –Torotot, Asis (soleil), et Ilat (pluie) ; celui d’en bas est celui où vivent les humains, animaux, et plantes. Les humains sont responsables du royaume qu’ils habitent, mais ils reposent sur les divinités pour atteindre et maintenir la paix et la prospérité. Ils vouent un culte à de nombreuses déités tels que le soleil et la lune et croient dans l’esprit de la mort. Les Pokot communiquent avec leurs déités par la prière et le sacrifice. Ils les accomplissent lors de festivals ethniques et de danses. Les oracles sont responsables du maintien de l’équilibre spirituel à l’intérieur de la communauté. Ils sont superstitieux et croient aux sortilèges, c’est pourquoi parfois ils invoquent des sortilèges de chance protecteurs. Ils ont des prophètes, hommes ou femmes, qui voient dans le futur et conseillent, habituellement au moyen de sacrifices d’animaux. Leurs capacités sont considérées comme un don divin. Les histoires claniques racontent les changements de leurs lieux de vie, à travers des poèmes et chansons, mettant en avant la vulnérabilité des êtres humains et l’importance de pouvoirs supernaturels qui les aident à surpasser la faim, la soif, et même la mort. Les cérémonies marquent les transitions dans la vie sociale des individus. Parmi celles-ci on compte : la purification d’un couple attendant leur premier enfant ; celle d’enfants nouveaux-nés et de leurs mères ; la purification de jumeaux et d’autres enfantgs qui sont nés dans des circonstances inhabituelles ; l’initiation pour hommes et femmes ; le mariage ; le sapana, une cérémonie pour la majorité chez les hommes ; le solstice d’été ; la moisson ; et les cérémonies de soins. Le rite de passage le plus important pour la plupart des Pokot est la circoncision pour les garçons et la clitorectomie pour les filles. Ces rites consistent en une série de cérémonies basées sur le voisinage, soulignant l’importance d’avoir une bonne conduite. Lorsque les garçons sont circoncis, ils deviennent membres de l’une des huit classes d’âge. Les femmes n’appartiennent à aucune classe d’âge. Après l’excision, pour plusieurs mois, les filles portent une painture blanche sur le visage et une capuche fait de cuir noirci au charbon de bois et à l’huile. Cela signifie qu’elle sont intouchables jusqu’à la cérémonie lepan, qui marque le passage à l’état de femme. Contrairement à d’autres tribus, les Pokot gardent l’affiliation à leur clan toute leur vie, il n’y a aucune rupture lors du mariage. De façon surprenante, l’accord avant le mariage est réalisé grâce à des cadeaux de la part du futur époux et de sa famille, à la fiancée et sa famille (et non le contraire), souvent pour une période donnée d’année. Cela implique souvent le don d’une association de bétail, biens, et argent à la famille de la mariée, et l’attribution de vaches à lait et des droits fonciers à la mariée. Le lien entre le mari et la femme dure pendant 3 générations, après quoi les mariages peuvent de nouveau avoir lieu entre les deux groupes. La polygamie existes mais ne prévaut pas chez les hommes de moins de 40 ans. Les esprits des plus vieux anticipent la réincarnation chez leurs descendants vivants : quand on dit d’un enfant qu’il ressemble à son aîné, le même nom lui est donné. Les disputes sont résolues dans des conseils de voisinage et dans les tribunaux du gouvernement. Certaines des sanctions incluent le déshonneur, la malédiction et l’ensorcellement.

 

© 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.

 

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.

Take comfort - if you make it past the incisors, those molars don't look all that bad

Well formed teeth were identified in a mature cystic teratoma (dermoid cyst) of the ovary.

 

Here is another example: www.flickr.com/photos/lunarcaustic/2598011697/in/photostream

It's not hard to guess what made these tooth marks. A beaver used his massive incisors to fell this tree. He ate the bark and then used the log as part of the structure to build his lodge.

Impala - Fast food of the African bush!

The impala even has the distinctive MacDonald's "M" on its rump and are also called predator take-aways. There are thousands of them in the Kruger Park and we get so used to spotting them that eventually we just ignore them.

Impalas have evolved a number of unique adaptations that allow them to thrive in their dangerous environment.

Grooming and tick removal are high on the list of survival skills. The impala is the only hoofed animal that allogrooms - mutual grooming from one animal to another - as well as grooming itself.

 

It is also the smallest antelope that tolerates oxpecker birds to assist in removing ticks. Ticks can reduce blood reserves exposing the antelope to disease and malnutrition. To assist them in grooming, impalas possess an "antelope's toothcomb" comprised of canines and incisors adapted for removing ticks and other parasites. By allogrooming they get rid of ticks etc in the unreachable places, like around the ears, head and neck. When it comes to the area under the tails the two black stripes of the MacDonalds logo come into play. The constantly wagging tail of the impala brushes the ticks towards the warmer black hair where the impala can reach with its teeth.

Unlike most animals, the impalas graze and browse, thereby maximising the availability of food. For safety they move in herds as large as the available food will allow. They scatter in all directions if a predator should charge, leaping in strides of up to 12 meters. Impala ewes give birth away from the herd and rejoins with her calf within two days. With lambs in the herd, vigilance is sharpened, but the lambs still fall prey to wild dogs and other predators.

Even though they are considered predator "fast food", their numbers are increasing and these graceful antelope will not be on the endangered list for some time to come.

Source: Getaway Magazine - January 2004

  

Mankwe Way

Pilanesberg National Park

Northwest Province

South Africa

I've been waiting 1.5 years for this impacted incisor to make its appearance.

It also looks like I'm in the need of a wax. Embarrassing.

Brock was sound asleep next to me and it led to a moment of bizarre inspiration

Wanted to do a series about untold adventures of the Kamen Riders in Ventara.

 

Top to bottom (focused characters): Incisor, Black Knight, Dragon Knight, Strike, Torque.

 

Figma Kamen Rider Dragon Knight action figures by Good Smile Company.