Jellyfish, also known sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.

 

Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle. The medusa is normally the sexual phase, which produces planula larvae; these then disperse widely and enter a sedentary polyp phase, before reaching sexual maturity.

 

Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.

 

Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy.

 

They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.

 

The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.

  

Names

The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies (ctenophores, another phylum). The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word "fish" with its modern connotation of an animal with a backbone, though shellfish, cuttlefish and starfish are not vertebrates either. In scientific literature, "jelly" and "jellyfish" have been used interchangeably. Many sources refer to only scyphozoans as "true jellyfish".

 

A group of jellyfish is called a "smack" or a "smuck".

 

Definition

The term jellyfish broadly corresponds to medusae, that is, a life-cycle stage in the Medusozoa. The American evolutionary biologist Paulyn Cartwright gives the following general definition:

 

Typically, medusozoan cnidarians have a pelagic, predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked].

 

The Merriam-Webster dictionary defines jellyfish as follows:

 

A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells.

 

Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies and certain salps jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.

 

The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with on the following cladogram of the animal kingdom:

 

Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.

 

Taxonomy

The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after the polyps. Medusozoans have tetramerous symmetry, with parts in fours or multiples of four.

 

The four major classes of medusozoan Cnidaria are:

Scyphozoa are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.

Cubozoa (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.

Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. Hydrozoa show great diversity of lifestyle; some species maintain the polyp form for their entire life and do not form medusae at all (such as Hydra, which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.

Staurozoa (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle. Until recently, Staurozoa were classified within the Scyphozoa.

There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.

 

Fossil history

Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is Burgessomedusa from the mid Cambrian Burgess Shale of Canada, which is likely either a stem group of box jellyfish (Cubozoa) or Acraspeda (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent ctenophores instead.

 

Anatomy

The main feature of a true jellyfish is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea, which forms the hydrostatic skeleton of the animal. 95% or more of the mesogloea consists of water, but it also contains collagen and other fibrous proteins, as well as wandering amoebocytes which can engulf debris and bacteria. The mesogloea is bordered by the epidermis on the outside and the gastrodermis on the inside. The edge of the bell is often divided into rounded lobes known as lappets, which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia, and the margin of the bell often bears tentacles.

  

Anatomy of a scyphozoan jellyfish

On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with the mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below. The mouth opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to the exterior, perhaps supplying good oxygenation to the gonads. Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal. Cilia in these canals circulate the fluid in a regular direction.

  

Discharge mechanism of a nematocyst

The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates, allowing box jellyfish to swim faster than true jellyfish. Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia. Stalked jellyfish are attached to a solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth.

 

Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift. The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called a "nerve net" is located in the epidermis. Although traditionally thought not to have a central nervous system, nerve net concentration and ganglion-like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.

 

In many species of jellyfish, the rhopalia include ocelli, light-sensitive organs able to tell light from dark. These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into the open lagoon, where they feed, and back again.

 

Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition, supposedly making them one of the few kinds of animal to have a 360-degree view of its environment.

 

Box jellyfish eye

The study of jellyfish eye evolution is an intermediary to a better understanding of how visual systems evolved on Earth. Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization.

 

Evolution

Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that is capable of multiple task-guided behaviors.

 

Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures. Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates. The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision. Increased habitat and task complexity has favored the high-resolution visual systems common in derived cnidarians such as box jellyfish.

 

Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. Extraocular photoreception (a form of non-directional photoreception), is the most basic form of light sensitivity and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans) and other light-guided behaviors responsive to the intensity and spectrum of light. Extraocular photoreception can function additionally in positive phototaxis (in planula larvae of hydrozoans), as well as in avoiding harmful amounts of UV radiation via negative phototaxis. Directional photoreception (the ability to perceive direction of incoming light) allows for more complex phototactic responses to light, and likely evolved by means of membrane stacking. The resulting behavioral responses can range from guided spawning events timed by moonlight to shadow responses for potential predator avoidance. Light-guided behaviors are observed in numerous scyphozoans including the common moon jelly, Aurelia aurita, which migrates in response to changes in ambient light and solar position even though they lack proper eyes.

 

The low-resolution visual system of box jellyfish is more derived than directional photoreception, and thus box jellyfish vision represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and spatial resolution. This is different from the high-resolution vision that is observed in camera or compound eyes of vertebrates and cephalopods that rely on focusing optics. Critically, the visual systems of box jellyfish are responsible for guiding multiple tasks or behaviors in contrast to less derived visual systems in other jellyfish that guide single behavioral functions. These behaviors include phototaxis based on sunlight (positive) or shadows (negative), obstacle avoidance, and control of swim-pulse rate.

 

Box jellyfish possess "proper eyes" (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot. In fact, they are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision. However, the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability. The lack of the ability to focus is due to the focal length exceeding the distance to the retina, thus generating unfocused images and limiting spatial resolution. The visual system is still sufficient for box jellyfish to produce an image to help with tasks such as object avoidance.

 

Utility as a model organism

Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses. The comparison of these attributes to more derived visual systems can allow for a further understanding of how the evolution of more derived visual systems may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.

 

Characteristics

Box jellyfish visual systems are both diverse and complex, comprising multiple photosystems. There is likely considerable variation in visual properties between species of box jellyfish given the significant inter-species morphological and physiological variation. Eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology across species of box jellyfish.

 

Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories. These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes. The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation. The larger of the complex eyes contains a cellular cornea created by a mono ciliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.

 

Box jellyfish have multiple photosystems that comprise different sets of eyes. Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes photosystems that work collectively to control visually guided behaviors.

 

Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo phototransduction cascades (process of light absorption by photoreceptors) that are triggered by c-opsins. Available opsin sequences suggest that there are two types of opsins possessed by all cnidarians including an ancient phylogenetic opsin, and a sister ciliary opsin to the c-opsins group. Box jellyfish could have both ciliary and cnidops (cnidarian opsins), which is something not previously believed to appear in the same retina. Nevertheless, it is not entirely evident whether cnidarians possess multiple opsins that are capable of having distinctive spectral sensitivities.

 

Comparison with other organisms

Comparative research on genetic and molecular makeup of box jellyfishes' eyes versus more derived eyes seen in vertebrates and cephalopods focuses on: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.

 

Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes. Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts. These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has led to the conclusion that PaxB was a primordial gene in eye evolution, and that the eyes of all organisms likely share a common ancestor.

 

The lens structure of box jellyfish appears very similar to those of other organisms, but the crystallins are distinct in both function and appearance. Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses. This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms' lenses exhibit.

 

All four of the visual systems of box jellyfish species investigated with detail (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora) have invaginated synapses, but only in the upper and lower lensed eyes. Different densities were found between the upper and lower lenses, and between species. Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.

 

Evolution as a response to natural stimuli

The primary adaptive responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness. Interestingly, some box jellyfish species' eyes appear to have evolved more focused vision in response to their habitat.

 

Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches across three species of box jellyfish (Chironex fleckeri, Chiropsella bronzie, and Carukia barnesi). Behavioral studies suggest that faster pupil contraction rates allow for greater object avoidance, and in fact, species with more complex habitats exhibit faster rates. Ch. bronzie inhabit shallow beach fronts that have low visibility and very few obstacles, thus, faster pupil contraction in response to objects in their environment is not important. Ca. barnesi and Ch. fleckeri are found in more three-dimensionally complex environments like mangroves with an abundance of natural obstacles, where faster pupil contraction is more adaptive. Behavioral studies support the idea that faster pupillary contraction rates assist with obstacle avoidance as well as depth adjustments in response to differing light intensities.

 

Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This relates to the pupil's response to shifts between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function. The lower lens-eyes contain pigmented photoreceptors and long pigment cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eyes play a concentrated role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon). The upper lens of Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora (a box jellyfish species that tends to live in mangroves) does. The ability to use light to visually guide behavior is not of as much importance to Ch. bronzie as it is to species in more obstacle-filled environments. Differences in visually guided behavior serve as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.

 

Largest and smallest

Jellyfish range from about one millimeter in bell height and diameter, to nearly 2 metres (6+1⁄2 ft) in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.

 

The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 millimetres (1⁄32 in) to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools; many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope. They can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps; some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months. The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter.

 

The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m (119 ft 9 in) long (though most are nowhere near that large). They have a moderately painful, but rarely fatal, sting. The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found in some, but not all years in the waters of Japan, Korea and China in summer and autumn is another candidate for "largest jellyfish", in terms of diameter and weight, since the largest Nomura's jellyfish in late autumn can reach 2 m (6 ft 7 in) in bell (body) diameter and about 200 kg (440 lb) in weight, with average specimens frequently reaching 0.9 m (2 ft 11 in) in bell diameter and about 150 kg (330 lb) in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the Lion's Mane, whose bell diameter can reach 1 m (3 ft 3 in).

 

The rarely encountered deep-sea jellyfish Stygiomedusa gigantea is another candidate for "largest jellyfish", with its thick, massive bell up to 100 cm (3 ft 3 in) wide, and four thick, "strap-like" oral arms extending up to 6 m (19+1⁄2 ft) in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.

 

Desmonema glaciale, which lives in the Antarctic region, can reach a very large size (several meters). Purple-striped jelly (Chrysaora colorata) can also be extremely long (up to 15 feet).

 

Life history and behavior

Life cycle

Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae and then transform into adult medusae. In some species certain stages may be skipped.

 

Upon reaching adult size, jellyfish spawn regularly if there is a sufficient supply of food. In most species, spawning is controlled by light, with all individuals spawning at about the same time of day; in many instances this is at dawn or dusk. Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. In a few species, the sperm swim into the female's mouth, fertilizing the eggs within her body, where they remain during early development stages. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.

 

The planula is a small larva covered with cilia. When sufficiently developed, it settles onto a firm surface and develops into a polyp. The polyp generally consists of a small stalk topped by a mouth that is ringed by upward-facing tentacles. The polyps resemble those of closely related anthozoans, such as sea anemones and corals. The jellyfish polyp may be sessile, living on the bottom, boat hulls or other substrates, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates. Polyps may be solitary or colonial. Most polyps are only millimetres in diameter and feed continuously. The polyp stage may last for years.

 

After an interval and stimulated by seasonal or hormonal changes, the polyp may begin reproducing asexually by budding and, in the Scyphozoa, is called a segmenting polyp, or a scyphistoma. Budding produces more scyphistomae and also ephyrae. Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae. In a process known as strobilation, the polyp's tentacles are reabsorbed and the body starts to narrow, forming transverse constrictions, in several places near the upper extremity of the polyp. These deepen as the constriction sites migrate down the body, and separate segments known as ephyra detach. These are free-swimming precursors of the adult medusa stage, which is the life stage that is typically identified as a jellyfish. The ephyrae, usually only a millimeter or two across initially, swim away from the polyp and grow. Limnomedusae polyps can asexually produce a creeping frustule larval form, which crawls away before developing into another polyp. A few species can produce new medusae by budding directly from the medusan stage. Some hydromedusae reproduce by fission.

 

Lifespan

Little is known of the life histories of many jellyfish as the places on the seabed where the benthic forms of those species live have not been found. However, an asexually reproducing strobila form can sometimes live for several years, producing new medusae (ephyra larvae) each year.

 

An unusual species, Turritopsis dohrnii, formerly classified as Turritopsis nutricula, might be effectively immortal because of its ability under certain circumstances to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other organism. So far this reversal has been observed only in the laboratory.

 

Locomotion

Jellyfish locomotion is highly efficient. Muscles in the jellylike bell contract, setting up a start vortex and propelling the animal. When the contraction ends, the bell recoils elastically, creating a stop vortex with no extra energy input.

Using the moon jelly Aurelia aurita as an example, jellyfish have been shown to be the most energy-efficient swimmers of all animals. They move through the water by radially expanding and contracting their bell-shaped bodies to push water behind them. They pause between the contraction and expansion phases to create two vortex rings. Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction. Meanwhile, the second vortex ring starts to spin faster, sucking water into the bell and pushing against the centre of the body, giving a secondary and "free" boost forward. The mechanism, called passive energy recapture, only works in relatively small jellyfish moving at low speeds, allowing the animal to travel 30 percent farther on each swimming cycle. Jellyfish achieved a 48 percent lower cost of transport (food and oxygen intake versus energy spent in movement) than other animals in similar studies. One reason for this is that most of the gelatinous tissue of the bell is inactive, using no energy during swimming.

 

Ecology

Diet

Jellyfish are, like other cnidarians, generally carnivorous (or parasitic), feeding on planktonic organisms, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and voiding undigested waste through the mouth. They hunt passively using their tentacles as drift lines, or sink through the water with their tentacles spread widely; the tentacles, which contain nematocysts to stun or kill the prey, may then flex to help bring it to the mouth. Their swimming technique also helps them to capture prey; when their bell expands it sucks in water which brings more potential prey within reach of the tentacles.

 

A few species such as Aglaura hemistoma are omnivorous, feeding on microplankton which is a mixture of zooplankton and phytoplankton (microscopic plants) such as dinoflagellates. Others harbour mutualistic algae (Zooxanthellae) in their tissues; the spotted jellyfish (Mastigias papua) is typical of these, deriving part of its nutrition from the products of photosynthesis, and part from captured zooplankton. The upside-down jellyfish (Cassiopea andromeda) also has a symbiotic relationship with microalgae, but captures tiny animals to supplement their diet. This is done by releasing tiny balls of living cells composed of mesoglea. These use cilia to drive them through water and stinging cells which stun the prey. The blobs also seems to have digestive capabilities.

 

Predation

Other species of jellyfish are among the most common and important jellyfish predators. Sea anemones may eat jellyfish that drift into their range. Other predators include tunas, sharks, swordfish, sea turtles and penguins. Jellyfish washed up on the beach are consumed by foxes, other terrestrial mammals and birds. In general however, few animals prey on jellyfish; they can broadly be considered to be top predators in the food chain. Once jellyfish have become dominant in an ecosystem, for example through overfishing which removes predators of jellyfish larvae, there may be no obvious way for the previous balance to be restored: they eat fish eggs and juvenile fish, and compete with fish for food, preventing fish stocks from recovering.

 

Symbiosis

Some small fish are immune to the stings of the jellyfish and live among the tentacles, serving as bait in a fish trap; they are safe from potential predators and are able to share the fish caught by the jellyfish. The cannonball jellyfish has a symbiotic relationship with ten different species of fish, and with the longnose spider crab, which lives inside the bell, sharing the jellyfish's food and nibbling its tissues.

 

Main article: Jellyfish bloom

Jellyfish form large masses or blooms in certain environmental conditions of ocean currents, nutrients, sunshine, temperature, season, prey availability, reduced predation and oxygen concentration. Currents collect jellyfish together, especially in years with unusually high populations. Jellyfish can detect marine currents and swim against the current to congregate in blooms. Jellyfish are better able to survive in nutrient-rich, oxygen-poor water than competitors, and thus can feast on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are able to survive in warmer waters. Increased nutrients from agricultural or urban runoff with nutrients including nitrogen and phosphorus compounds increase the growth of phytoplankton, causing eutrophication and algal blooms. When the phytoplankton die, they may create dead zones, so-called because they are hypoxic (low in oxygen). This in turn kills fish and other animals, but not jellyfish, allowing them to bloom. Jellyfish populations may be expanding globally as a result of land runoff and overfishing of their natural predators. Jellyfish are well placed to benefit from disturbance of marine ecosystems. They reproduce rapidly; they prey upon many species, while few species prey on them; and they feed via touch rather than visually, so they can feed effectively at night and in turbid waters. It may be difficult for fish stocks to re-establish themselves in marine ecosystems once they have become dominated by jellyfish, because jellyfish feed on plankton, which includes fish eggs and larvae.

 

As suspected at the turn of this century, jellyfish blooms are increasing in frequency. Between 2013 and 2020 the Mediterranean Science Commission monitored on a weekly basis the frequency of such outbreaks in coastal waters from Morocco to the Black Sea, revealing a relatively high frequency of these blooms nearly all year round, with peaks observed from March to July and often again in the autumn. The blooms are caused by different jellyfish species, depending on their localisation within the Basin: one observes a clear dominance of Pelagia noctiluca and Velella velella outbreaks in the western Mediterranean, of Rhizostoma pulmo and Rhopilema nomadica outbreaks in the eastern Mediterranean, and of Aurelia aurita and Mnemiopsis leidyi outbreaks in the Black Sea.

 

Some jellyfish populations that have shown clear increases in the past few decades are invasive species, newly arrived from other habitats: examples include the Black Sea, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil).

 

Jellyfish blooms can have significant impact on community structure. Some carnivorous jellyfish species prey on zooplankton while others graze on primary producers. Reductions in zooplankton and ichthyoplankton due to a jellyfish bloom can ripple through the trophic levels. High-density jellyfish populations can outcompete other predators and reduce fish recruitment. Increased grazing on primary producers by jellyfish can also interrupt energy transfer to higher trophic levels.

 

During blooms, jellyfish significantly alter the nutrient availability in their environment. Blooms require large amounts of available organic nutrients in the water column to grow, limiting availability for other organisms. Some jellyfish have a symbiotic relationship with single-celled dinoflagellates, allowing them to assimilate inorganic carbon, phosphorus, and nitrogen creating competition for phytoplankton. Their large biomass makes them an important source of dissolved and particulate organic matter for microbial communities through excretion, mucus production, and decomposition. The microbes break down the organic matter into inorganic ammonium and phosphate. However, the low carbon availability shifts the process from production to respiration creating low oxygen areas making the dissolved inorganic nitrogen and phosphorus largely unavailable for primary production.

 

These blooms have very real impacts on industries. Jellyfish can outcompete fish by utilizing open niches in over-fished fisheries. Catch of jellyfish can strain fishing gear and lead to expenses relating to damaged gear. Power plants have been shut down due to jellyfish blocking the flow of cooling water. Blooms have also been harmful for tourism, causing a rise in stings and sometimes the closure of beaches.

 

Jellyfish form a component of jelly-falls, events where gelatinous zooplankton fall to the seafloor, providing food for the benthic organisms there. In temperate and subpolar regions, jelly-falls usually follow immediately after a bloom.

 

Habitats

Most jellyfish are marine animals, although a few hydromedusae inhabit freshwater. The best known freshwater example is the cosmopolitan hydrozoan jellyfish, Craspedacusta sowerbii. It is less than an inch (2.5 cm) in diameter, colorless and does not sting. Some jellyfish populations have become restricted to coastal saltwater lakes, such as Jellyfish Lake in Palau. Jellyfish Lake is a marine lake where millions of golden jellyfish (Mastigias spp.) migrate horizontally across the lake daily.

 

Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus Cassiopea typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.

 

Some species explicitly adapt to tidal flux. In Roscoe Bay, jellyfish ride the current at ebb tide until they hit a gravel bar, and then descend below the current. They remain in still waters until the tide rises, ascending and allowing it to sweep them back into the bay. They also actively avoid fresh water from mountain snowmelt, diving until they find enough salt.

  

Parasites

Jellyfish are hosts to a wide variety of parasitic organisms. They act as intermediate hosts of endoparasitic helminths, with the infection being transferred to the definitive host fish after predation. Some digenean trematodes, especially species in the family Lepocreadiidae, use jellyfish as their second intermediate hosts. Fish become infected by the trematodes when they feed on infected jellyfish.

 

Relation to humans

Jellyfish have long been eaten in some parts of the world. Fisheries have begun harvesting the American cannonball jellyfish, Stomolophus meleagris, along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.

 

Jellyfish are also harvested for their collagen, which is being investigated for use in a variety of applications including the treatment of rheumatoid arthritis.

 

Aquaculture and fisheries of other species often suffer severe losses – and so losses of productivity – due to jellyfish.

 

Products

Main article: Jellyfish as food

In some countries, including China, Japan, and Korea, jellyfish are a delicacy. The jellyfish is dried to prevent spoiling. Only some 12 species of scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food, mostly in southeast Asia. Rhizostomes, especially Rhopilema esculentum in China (海蜇 hǎizhé, 'sea stingers') and Stomolophus meleagris (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.

 

Traditional processing methods, carried out by a jellyfish master, involve a 20- to 40-day multi-phase procedure in which, after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed. Processing makes the jellyfish drier and more acidic, producing a crisp texture. Jellyfish prepared this way retain 7–10% of their original weight, and the processed product consists of approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.

 

In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.

 

Biotechnology

The hydromedusa Aequorea victoria was the source of green fluorescent protein, studied for its role in bioluminescence and later for use as a marker in genetic engineering.

Pliny the Elder reported in his Natural History that the slime of the jellyfish "Pulmo marinus" produced light when rubbed on a walking stick.

 

In 1961, Osamu Shimomura extracted green fluorescent protein (GFP) and another bioluminescent protein, called aequorin, from the large and abundant hydromedusa Aequorea victoria, while studying photoproteins that cause bioluminescence in this species. Three decades later, Douglas Prasher sequenced and cloned the gene for GFP. Martin Chalfie figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien later chemically manipulated GFP to produce other fluorescent colors to use as markers. In 2008, Shimomura, Chalfie and Tsien won the Nobel Prize in Chemistry for their work with GFP. Man-made GFP became widely used as a fluorescent tag to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. The fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene turns on in the same tissues and the same time as the normal gene, making a fusion of the normal protein with GFP attached to the end, illuminating the animal or cell reveals what tissues express that protein—or at what stage of development. The fluorescence shows where the gene is expressed.

 

Aquarium display

Jellyfish are displayed in many public aquariums. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible. Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits as in the Monterey Bay Aquarium feature precise water flows, typically in circular tanks to avoid trapping specimens in corners. The outflow is spread out over a large surface area and the inflow enters as a sheet of water in front of the outflow, so the jellyfish do not get sucked into it. As of 2009, jellyfish were becoming popular in home aquariums, where they require similar equipment.

 

Stings

Jellyfish are armed with nematocysts, a type of specialized stinging cell. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, but only some species' venom causes an adverse reaction in humans. In a study published in Communications Biology, researchers found a jellyfish species called Cassiopea xamachana which when triggered will release tiny balls of cells that swim around the jellyfish stinging everything in their path. Researchers described these as "self-propelling microscopic grenades" and named them cassiosomes.

 

The effects of stings range from mild discomfort to extreme pain and death. Most jellyfish stings are not deadly, but stings of some box jellyfish (Irukandji jellyfish), such as the sea wasp, can be deadly. Stings may cause anaphylaxis (a form of shock), which can be fatal. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava.

 

Vinegar (3–10% aqueous acetic acid) may help with box jellyfish stings but not the stings of the Portuguese man o' war. Clearing the area of jelly and tentacles reduces nematocyst firing. Scraping the affected skin, such as with the edge of a credit card, may remove remaining nematocysts. Once the skin has been cleaned of nematocysts, hydrocortisone cream applied locally reduces pain and inflammation. Antihistamines may help to control itching. Immunobased antivenins are used for serious box jellyfish stings.

 

In Elba Island and Corsica dittrichia viscosa is now used by residents and tourists to heal stings from jellyfish, bees and wasps pressing fresh leaves on the skin with quick results.

 

Mechanical issues

Jellyfish in large quantities can fill and split fishing nets and crush captured fish. They can clog cooling equipment, having disabled power stations in several countries; jellyfish caused a cascading blackout in the Philippines in 1999, as well as damaging the Diablo Canyon Power Plant in California in 2008. They can also stop desalination plants and ships' engines.

S’il vous plaît note: 1 lote = 20 pcs Manfrotto + 20 pcs clip titulaire + 20 pcs Bluetooth d’obturation = 60 pcs/lote

Caractéristiques de manfrotto:

100% tout neuf et de haute qualité

Poids léger,...

 

telephone.pascherenchine.com/products/60-pcs-bluetooth-ca...

Prototype of the Mercury, an infinitely extensible, open camera system that I developed over the past two years, with some help from others. This one is shown configured to shoot Instax Mini. I've modified the Diana Instant Back with new parts so that it can mate with the camera. It uses the Graflok 23 (medium format) standard mount.

The spot-billed pelican or grey pelican (Pelecanus philippensis) shot at Vedanthangal. Check out its clear eyes and spots in the bill that has given the bird its name.

 

Also check out the extended frills below its bill, which gives it the extraordinary ability to use it as a fishing net and catch fish. They can hold up to 50 fish at a time before swallowing them up. These pelicans are also able to kill and eat anything that fits within this extensible pouch in their lower bill.

50 pcs DHLFree profissional rainures sur bâton Mobile téléphone caméra trépied extensible portrait de poche Manfrotto

 

Facile à prendre photo!

Note: ce téléphone...

 

telephone.pascherenchine.com/products/50-pcs-dhlfree-groo...

Paper Wasp using extensible "arm" to retrieve and eat.

First GUI prototype of my new general purpose dataflow library: Fully extensible node architecture, asynchronous, event driven, multithreaded, JSON serialization.

 

The GUI aspect will only be an optional feature for building client friendly user interfaces. These classes will be fully skinnable. The NEdit core library is not intended to be a VVVV or QuartzComposer clone or similar. It's meant to provide an event driven graph model with parallel/distributed execution features, as well as useful/common node types. Events are propagated through the graph in a breadth-first approach with each event update running in its own thread. There will also be a support module for providing node types wrapping toxiclibs classes (as already shown above, e.g. SphereGenNode wraps SurfaceMeshBuilder, SceneObjectNode wraps Matrix4x4 & TriangleMesh etc.)

 

First release coming soon...

Soil profile: The Aimeliik series consists of forest soils characterized by relatively fertile topsoil over infertile subsoil. Reddish subsoil (at a depth of about 15 to 35 centimeters in this profile) overlies subsoil that still retains some characteristics of the parent material. The Aimeliik series is one of the most extensive series in Palau. This profile is in an area of map unit 603, Aimeliik silt loam, 30 to 50 percent slopes, in Melekeok State, Babeldaob Island. (Soil Survey of the Islands of Palau, Republic of Palau; by Jason L. Nemecek and Robert T. Gavenda, Natural Resources Conservation Service)

 

Landscape: Ancient manmade terraces in areas of Palau soils under grass on the western coast of Babeldaob Island. Fire-resistant pandanus trees remain on the grassland. The forested area consists primarily of Aimeliik soils.

 

The Aimeliik series consists of; very deep, well drained, soils that is shallow to an abrupt textural change. These soils formed in saprolite derived from basalt, andesite, dacite, volcanic breccias, tuff, or bedded tuff. Aimeliik soils are on all hillslope positions of hills on volcanic islands. Slope is 2 to 75 percent. The mean annual rainfall is about 3685 millimeters (145 inches), and the mean annual temperature is about 27 C (81 F.)

 

TAXONOMIC CLASS: Very-fine, halloysitic, isohyperthermic Typic Kandiperox

 

Control section: 25 to 100 centimeters (10 to 39 inches)

Thickness of the solum: 50 to 150 centimeters (20 to 59 inches)

Depth to bottom of diagnostic features:

Ochric epipedon 7 to 29 centimeters (3 to 11 inches)

Fibric soil materials 2 to 8 centimeters (1 to 3 inches)

Depth to diagnostic features:

Kandic horizon: 8 to 40 centimeters (3 to 16 inches)

Abrupt textural change: 8 to 40 centimeters (3 to 16 inches)

Thickness of diagnostic features:

Ochric epipedon: 8 to 40 centimeters (3 to 16 inches)

Kandic horizon: 26 to 125 centimeters (10 to 49 inches)

Fibric soil materials: 1 to 10 centimeters (0 to 4 inches)

Linear extensibility: 4 to 11 percent, weighted average RV is 6 percent

Surface Fragments: Rock fragments are vesicular petroferric fragments, tuff, ironstone and gibbsite concretions; 0 to 15 percent total rock fragments; 0 to 15 percent gravel; 0 to 15 percent cobbles

Saturated hydraulic conductivity: High in the subsoil and moderately high in the underlying material.

 

These soils are in mixed-upland forests plant communities and are used for native vegetation, watershed, and slash and burn or agroforestry cultivation of subsistence crops. A few areas are used for urban development. Agroforestry ground crops include; beans, cassava, kang kong, melon, peppers, noni, okra, pineapple, piper betle, pumpkin, taro squash, sugar cane, taro, and yams. Agroforestry tree crops include; avocados, bananas, betel nut, breadfruit, football fruit, guava, Inocarpus fagifer, keam, lemons, mango, medicinal plants, mountain apple, ngel, star fruit, titimel, and tropical almond. Most areas are in native tropical rainforest or, to a lesser extent, patches of forest in perennial grassland that is burned by humans almost annually. Native vegetation includes; (canopy) Pinanga insignis, Cyathea sp, Alphitonia carolinensis, Pouteria obovata, Fagraea ksid, Callophyllum inophyllum var. wakamatsui, Rhus taitensis, (understory) Atuna corymbosa, Garcinia matudai, Pleome multiflora, Finschia chloraxantha, Manilkara udoid, Symplocos racemosa, Campnosperma brevipetiolata, Cerbera floribunda.

 

DISTRIBUTION AND EXTENT: MLRA 193 Volcanic Islands of Western Micronesia, Republic of Palau. These soils of these series are of large extent; about 50,000 acres in size. They are mapped on the islands of island of Babeldaob and to a lesser extent on Koror and Arakabesan.

 

The A horizon does not become dry for longer than 4 consecutive days and 24 cumulative days per year during the dry season (February, March, and April). Drying only occurs under bare soil conditions. The soil does not meet the definition of an oxic horizon because the clay content increases by more than 8 percent within 15 centimeters (6 inches.) The Ngardok forested series was correlated with Aimeliik, bedded tuff. The Aimeliik, bedded tuff substratum has a platy structure and seems to be more erosive when vegetation is removed. In addition, when Aimeliik occurs near Ollei and Nekken series the rock fragments are likely to be hard basalt and indurated tuff.

 

Particle-size distribution measurements are usually not reliable for tropical soils; therefore, apparent field textures and the corresponding mid-point values of texture classes were used rather than laboratory analysis for particle sizes. Particle size distribution is difficult to determine in tropical soils because of the tendency to form water-stable aggregates. The poor soil dispersion in laboratory analyses reflects the water-stable aggregates of clay in silt and sand-sized "particles." Therefore, the soils may have large clay content but physically they behave as coarser textures.

 

For additional information about the survey area, visit:

www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/pacific_basin/...

 

For a detailed soil description, visit:

soilseries.sc.egov.usda.gov/OSD_Docs/A/AIMELIIK.html

 

For acreage and geographic distribution, visit:

casoilresource.lawr.ucdavis.edu/see/#aimeliik

 

See my profil for more information!

Bats are mammals of the order Chiroptera (/kaɪˈrɒptərə/; from the Ancient Greek: χείρ - cheir, "hand" and Ancient Greek: πτερόν - pteron, "wing" whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, can only glide for short distances. Bats do not flap their entire forelimbs, as birds do, but instead flap their spread-out digits, which are very long and covered with a thin membrane or patagium.

 

Bats are the second largest order of mammals (after the rodents), representing about 20% of all classified mammal species worldwide, with about 1,240 bat species divided into two suborders: the less specialized and largely fruit-eating megabats, or flying foxes, and the highly specialized and echolocating microbats. About 70% of bat species are insectivores. Most of the rest are frugivores, or fruit eaters. A few species, such as the fish-eating bat, feed from animals other than insects, with the vampire bats being hematophagous, or feeding on blood.

 

Bats are present throughout most of the world, with the exception of extremely cold regions. They perform the vital ecological roles of pollinating flowers and dispersing fruit seeds; many tropical plant species depend entirely on bats for the distribution of their seeds. Bats are economically important, as they consume insect pests, reducing the need for pesticides. The smallest bat is the Kitti's hog-nosed bat, measuring 29–34 mm in length, 15 cm across the wings and 2–2.6 g in mass. It is also arguably the smallest extant species of mammal, with the Etruscan shrew being the other contender. The largest species of bat are a few species of Pteropus (fruit bats or flying foxes) and the giant golden-crowned flying fox with a weight up to 1.6 kg and wingspan up to 1.7 m.

 

The Mexican free-tailed bat is the fastest flying animal in horizontal flight.

 

ETYMOLOGY

In many languages, the word for "bat" is cognate with the word for "mouse": for example, chauve-souris ("bald-mouse") in French, murciélago ("blind mouse") in Spanish, saguzahar ("old mouse") in Basque, летучая мышь ("flying mouse") in Russian, slijepi miš ("blind mouse") in Bosnian, nahkhiir ("leather mouse") in Estonian, vlermuis (winged mouse) in Afrikaans, from the Dutch word vleermuis (from Middle Dutch "winged mouse").

 

An older English name for bats is flittermouse, which matches their name in other Germanic languages (for example German Fledermaus and Swedish fladdermus), related to fluttering of wings. Middle English had bakke, which may have undergone a shift from -k- to -t- influenced by Latin blatta, "moth, nocturnal insect".

 

CLASSIFICATION AND EVOLUTION

Bats are placental mammals. Bats were formerly thought to have been most closely related to the flying lemurs, treeshrews, and primates, but recent molecular cladistics research indicates that they actually belong to Laurasiatheria, a diverse group also containing Carnivora and Artiodactyla.

 

The two traditionally recognized suborders of bats are:

 

- Megachiroptera (megabats)

- Microchiroptera (microbats/echolocating bats)

 

Not all megabats are larger than microbats. The major distinctions between the two suborders are:

 

- Microbats use echolocation; with the exception of the genus Rousettus, megabats do not.

- Microbats lack the claw at the second finger of the forelimb.

- The ears of microbats do not close to form a ring; the edges are separated from each other at the base of the ear.

- Microbats lack underfur; they are either naked or have guard hairs.

 

Megabats eat fruit, nectar, or pollen. Most microbats eat insects; others may feed on fruit, nectar, pollen, fish, frogs, small mammals, or the blood of animals. Megabats have well-developed visual cortices and show good visual acuity, while microbats rely on echolocation for navigation and finding prey.

 

The phylogenetic relationships of the different groups of bats have been the subject of much debate. The traditional subdivision between Megachiroptera and Microchiroptera reflects the view that these groups of bats have evolved independently of each other for a long time, from a common ancestor already capable of flight. This hypothesis recognized differences between microbats and megabats and acknowledged that flight has only evolved once in mammals. Most molecular biological evidence supports the view that bats form a single or monophyletic group.

 

Researchers have proposed alternative views of chiropteran phylogeny and classification, but more research is needed.

 

In the 1980s, a hypothesis based on morphological evidence was offered that stated the Megachiroptera evolved flight separately from the Microchiroptera. The so-called flying primate hypothesis proposes that, when adaptations to flight are removed, the Megachiroptera are allied to primates by anatomical features not shared with Microchiroptera. One example is that the brains of megabats show a number of advanced characteristics that link them to primates. Although recent genetic studies strongly support the monophyly of bats, debate continues as to the meaning of available genetic and morphological evidence.

 

Genetic evidence indicates that megabats originated during the early Eocene and should be placed within the four major lines of microbats.

 

Consequently, two new suborders based on molecular data have been proposed. The new suborder of Yinpterochiroptera includes the Pteropodidae, or megabat family, as well as the families Rhinolophidae, Hipposideridae, Craseonycteridae, Megadermatidae, and Rhinopomatidae The other new suborder, Yangochiroptera, includes all of the remaining families of bats (all of which use laryngeal echolocation). These two new suborders are strongly supported by statistical tests. Teeling (2005) found 100% bootstrap support in all maximum likelihood analyses for the division of Chiroptera into these two modified suborders. This conclusion is further supported by a 15-base-pair deletion in BRCA1 and a seven-base-pair deletion in PLCB4 present in all Yangochiroptera and absent in all Yinpterochiroptera. Perhaps most convincingly, a phylogenomic study by Tsagkogeorga et al (2013) showed that the two new proposed suborders were supported by analyses of thousands of genes.

 

The chiropteran phylogeny based on molecular evidence is controversial because microbat paraphyly implies that one of two seemingly unlikely hypotheses occurred. The first suggests that laryngeal echolocation evolved twice in Chiroptera, once in Yangochiroptera and once in the rhinolophoids. The second proposes that laryngeal echolocation had a single origin in Chiroptera, was subsequently lost in the family Pteropodidae (all megabats), and later evolved as a system of tongue-clicking in the genus Rousettus.

 

Analyses of the sequence of the "vocalization" gene, FoxP2, were inconclusive as to whether laryngeal echolocation was secondarily lost in the pteropodids or independently gained in the echolocating lineages. However, analyses of the "hearing" gene, Prestin, seemed to favor the independent gain in echolocating species rather than a secondary loss in the pteropodids.

 

In addition to Yinpterochiroptera and Yangochiroptera, the names Pteropodiformes and Vespertilioniformes have also been proposed for these suborders. Under this new proposed nomenclature, the suborder Pteropodiformes includes all extant bat families more closely related to the genus Pteropus than the genus Vespertilio, while the suborder Vespertilioniformes includes all extant bat families more closely related to the genus Vespertilio than to the genus Pteropus.

 

Little fossil evidence is available to help map the evolution of bats, since their small, delicate skeletons do not fossilize very well. However, a Late Cretaceous tooth from South America resembles that of an early microchiropteran bat. Most of the oldest known, definitely identified bat fossils were already very similar to modern microbats. These fossils, Icaronycteris, Archaeonycteris, Palaeochiropteryx and Hassianycteris, are from the early Eocene period, 52.5 million years ago. Archaeopteropus, formerly classified as the earliest known megachiropteran, is now classified as a microchiropteran.

 

Bats were formerly grouped in the superorder Archonta, along with the treeshrews (Scandentia), colugos (Dermoptera), and the primates, because of the apparent similarities between Megachiroptera and such mammals. Genetic studies have now placed bats in the superorder Laurasiatheria, along with carnivorans, pangolins, odd-toed ungulates, even-toed ungulates, and cetaceans. A recent study by Zhang et al. places Chiroptera as a sister taxon to the clade Perissodactyla (which includes horses and other odd-toed ungulates). However, the first phylogenomic analysis of bats shows that they are not sisters to Perissodactyla, instead they are sisters to a larger group that includes ungulates and carnivores.

 

Megabats primarily eat fruit or nectar. In New Guinea, they are likely to have evolved for some time in the absence of microbats, which has resulted in some smaller megabats of the genus Nyctimene becoming (partly) insectivorous to fill the vacant microbat ecological niche. Furthermore, some evidence indicates that the fruit bat genus Pteralopex from the Solomon Islands, and its close relative Mirimiri from Fiji, have evolved to fill some niches that were open because there are no nonvolant or nonflying mammals on those islands.

 

FOSSIL BATS

Fossilized remains of bats are few, as they are terrestrial and light-boned. Only an estimated 12% of the bat fossil record is complete at the genus level. Fossil remains of an Eocene bat, Icaronycteris, were found in 1960. Another Eocene bat, Onychonycteris finneyi, was found in the 52-million-year-old Green River Formation in Wyoming, United States, in 2003. This intermediate fossil has helped to resolve a long-standing disagreement regarding whether flight or echolocation developed first in bats. The shape of the rib cage, faceted infraspious fossa of the scapula, manus morphology, robust clavicle, and keeled sternum all indicated Onychonycteris was capable of powered flight. However, the well-preserved skeleton showed that the small cochlea of the inner ear did not have the morphology necessary to echolocate. O. finneyi lacked an enlarged orbical apophysis on the malleus, and a stylohyal element with an expanded paddle-like cranial tip - both of which are characteristics linked to echolocation in other prehistoric and extant bat species. Because of these absences, and the presence of characteristics necessary for flight, Onychonycteris provides strong support for the “flight first” hypothesis in the evolution of flight and echolocation in bats.

 

The appearance and flight movement of bats 52.5 million years ago were different from those of bats today. Onychonycteris had claws on all five of its fingers, whereas modern bats have at most two claws appearing on two digits of each hand. It also had longer hind legs and shorter forearms, similar to climbing mammals that hang under branches, such as sloths and gibbons. This palm-sized bat had short, broad wings, suggesting that it could not fly as fast or as far as later bat species. Instead of flapping its wings continuously while flying, Onychonycteris likely alternated between flaps and glides while in the air. Such physical characteristics suggest that this bat did not fly as much as modern bats do, rather flying from tree to tree and spending most of its waking day climbing or hanging on the branches of trees. The distinctive features noted on the Onychonycteris fossil also support the claim that mammalian flight most likely evolved in arboreal gliders, rather than terrestrial runners. This model of flight development, commonly known as the "trees-down" theory, implies that bats attained powered flight by taking advantage of height and gravity, rather than relying on running speeds fast enough for a ground-level take off.

 

The mid-Eocene genus Necromantis is one of the earliest examples of bats specialised to hunt vertebrate prey, as well as one of the largest bats of its epoch. The late-Eocene Witwatia is another similarly large predatory bat, while Aegyptonycteris is among the first and largest omnivorous bat species.

 

The extinct bats Palaeochiropteryx tupaiodon and Hassianycteris kumari are the first fossil mammals to have their colouration discovered, both of a reddish brown.

 

HABITATS

Flight has enabled bats to become one of the most widely distributed groups of mammals.[38] Apart from the Arctic, the Antarctic and a few isolated oceanic islands, bats exist all over the world. Bats are found in almost every habitat available on Earth. Different species select different habitats during different seasons, ranging from seasides to mountains and even deserts, but bat habitats have two basic requirements: roosts, where they spend the day or hibernate, and places for foraging. Most temperate species additionally need a relatively warm hibernation shelter. Bat roosts can be found in hollows, crevices, foliage, and even human-made structures, and include "tents" the bats construct by biting leaves.

 

The United States is home to an estimated 45 to 48 species of bats. The three most common species are Myotis lucifugus (little brown bat), Eptesicus fuscus (big brown bat), and Tadarida brasiliensis (Mexican free-tailed bat). The little and the big brown bats are common throughout the northern two-thirds of the country, while the Mexican free-tailed bat is the most common species in the southwest, sometimes even appearing in portions of the Southeast.

 

ANATOMY

WINGS

The finger bones of bats are much more flexible than those of other mammals, owing to their flattened cross-section and to low levels of minerals, such as calcium, near their tips. In 2006, Sears et al. published a study that traces the elongation of manual bat digits, a key feature required for wing development, to the upregulation of bone morphogenetic proteins (Bmps). During embryonic development, the gene controlling Bmp signaling, Bmp2, is subjected to increased expression in bat forelimbs - resulting in the extension of the offspring's manual digits. This crucial genetic alteration helps create the specialized limbs required for volant locomotion. Sears et al. (2006) also studied the relative proportion of bat forelimb digits from several extant species and compared these with a fossil of Lcaronycteris index, an early extinct species from approximately 50 million years ago. The study found no significant differences in relative digit proportion, suggesting that bat wing morphology has been conserved for over 50 million years.

 

The wings of bats are much thinner and consist of more bones than the wings of birds, allowing bats to maneuver more accurately than the latter, and fly with more lift and less drag. By folding the wings in toward their bodies on the upstroke, they save 35 percent energy during flight. The membranes are also delicate, ripping easily; however, the tissue of the bat's membrane is able to regrow, such that small tears can heal quickly. The surface of their wings is equipped with touch-sensitive receptors on small bumps called Merkel cells, also found on human fingertips. These sensitive areas are different in bats, as each bump has a tiny hair in the center, making it even more sensitive and allowing the bat to detect and collect information about the air flowing over its wings, and to fly more efficiently by changing the shape of its wings in response. An additional kind of receptor cell is found in the wing membrane of species that use their wings to catch prey. This receptor cell is sensitive to the stretching of the membrane. The cells are concentrated in areas of the membrane where insects hit the wings when the bats capture them.

 

CIRCULATORY SYSTEM

Bats seem to make use of particularly strong venomotion (rhythmic contraction of venous wall muscles). In most mammals, the walls of the veins provide mainly passive resistance (maintaining their shape as deoxygenated blood flows through them), but in bats they appear to actively support blood flow back to the heart with this pumping action.

 

Bats also possess a system of sphincter valves on the arterial side of the vascular network that runs along the edge of their wings. In the fully open state, these allow oxygenated blood to flow through the capillary network across the flight membrane (i.e. wing surface), but when contracted, they shunt flow directly to the veins, bypassing the wing capillaries. This is likely an important tool for thermoregulation, allowing the bats to control the amount of heat exchanged through the thin flight membrane (many other mammals use the capillary network in oversized ears for the same purpose).

 

OTHER

The teeth of microbats resemble insectivorans. They are very sharp to bite through the hardened armor of insects or the skin of fruit.

 

The tube-lipped nectar bat (Anoura fistulata) has the longest tongue of any mammal relative to its body size. This is beneficial to them in terms of pollination and feeding. Their long, narrow tongues can reach deep into the long cup shape of some flowers. When the tongue retracts, it coils up inside its rib cage.

 

Bats possess highly adapted lung systems to cope with the pressures of powered-flight. Flight is an energetically taxing aerobic activity and requires large amounts of oxygen to be sustained. In bats, the relative alveolar surface area and pulmonary capillary blood volume are significantly larger than most other small quadrupedal mammals

 

ECHOLOCATION

Bat echolocation is a perceptual system where ultrasonic sounds are emitted specifically to produce echoes. By comparing the outgoing pulse with the returning echoes, the brain and auditory nervous system can produce detailed images of the bat's surroundings. This allows bats to detect, localize, and even classify their prey in complete darkness. At 130 decibels in intensity, bat calls are some of the most intense, airborne animal sounds.

 

To clearly distinguish returning information, bats must be able to separate their calls from the echoes that they receive. Microbats use two distinct approaches.

- Low duty cycle echolocation: Bats can separate their calls and returning echoes by time. Bats that use this approach time their short calls to finish before echoes return. This is important because these bats contract their middle ear muscles when emitting a call, so they can avoid deafening themselves. The time interval between the call and echo allows them to relax these muscles, so they can clearly hear the returning echo. The delay of the returning echoes provides the bat with the ability to estimate the range to their prey.

- High duty cycle echolocation: Bats emit a continuous call and separate pulse and echo in frequency. The ears of these bats are sharply tuned to a specific frequency range. They emit calls outside of this range to avoid self-deafening. They then receive echoes back at the finely tuned frequency range by taking advantage of the Doppler shift of their motion in flight. The Doppler shift of the returning echoes yields information relating to the motion and location of the bat's prey. These bats must deal with changes in the Doppler shift due to changes in their flight speed. They have adapted to change their pulse emission frequency in relation to their flight speed so echoes still return in the optimal hearing range.

 

The new Yinpterochiroptera and Yangochiroptera classification of bats, supported by molecular evidence, suggests two possibilities for the evolution of echolocation. It may have been gained once in a common ancestor of all bats and was then subsequently lost in the Old World fruit bats, only to be regained in the horseshoe bats, or echolocation evolved independently in both the Yinpterochiroptera and Yangochiroptera lineages.

 

Two groups of moths exploit a bat sense to echolocate: tiger moths produce ultrasonic signals to warn the bats that they (the moths) are chemically protected or aposematic, other moth species produce signals to jam bat echolocation. Many moth species have a hearing organ called a tympanum, which responds to an incoming bat signal by causing the moth's flight muscles to twitch erratically, sending the moth into random evasive maneuvers.

 

In addition to echolocating prey, bat ears are sensitive to the fluttering of moth wings, the sounds produced by tymbalate insects, and the movement of ground-dwelling prey, such as centipedes, earwigs, etc. The complex geometry of ridges on the inner surface of bat ears helps to sharply focus not only echolocation signals, but also to passively listen for any other sound produced by the prey. These ridges can be regarded as the acoustic equivalent of a Fresnel lens, and may be seen in a large variety of unrelated animals, such as the aye-aye, lesser galago, bat-eared fox, mouse lemur, and others.

 

By repeated scanning, bats can mentally construct an accurate image of the environment in which they are moving and of their prey item.

 

OTHER SENSES

Although the eyes of most microbat species are small and poorly developed, leading to poor visual acuity, no species is blind. Microbats use vision to navigate, especially for long distances when beyond the range of echolocation, and species that are gleaners - that is, ones that attempt to swoop down from above to ambush insects, like crickets on the ground or moths up a tree, often have eyesight about as good as a rat's. Some species have been shown to be able to detect ultraviolet light, and most cave-dwelling species have developed the ability to utilize very dim light. They also have high-quality senses of smell and hearing. Bats hunt at night, reducing competition with birds, minimizing contact with certain predators, and travel large distances (up to 800 km) in their search for food.

 

Megabat species often have excellent eyesight as good as, if not better than, human vision. This eyesight is, unlike its microbat relations, adapted to both night and daylight vision and enables the bat to have some colour vision whereas the microbat sees in blurred shades of grey.

 

BEHAVIOUR

Most microbats are nocturnal and are active at twilight. A large portion of bats migrate hundreds of kilometres to winter hibernation dens, while some pass into torpor in cold weather, rousing and feeding when warm weather allows for insects to be active. Others retreat to caves for winter and hibernate for six months. Bats rarely fly in rain, as the rain interferes with their echolocation, and they are unable to locate their food.

 

The social structure of bats varies, with some leading solitary lives and others living in caves colonized by more than a million bats.[69] The fission-fusion social structure is seen among several species of bats. The term "fusion" refers to a large numbers of bats that congregate in one roosting area, and "fission" refers to breaking up and the mixing of subgroups, with individual bats switching roosts with others and often ending up in different trees and with different roostmates.

 

Studies also show that bats make various sounds in order to communicate with one another. Scientists in the field have listened to bats and have been able to associate certain sounds with certain behaviours that bats make after the sounds are made.

 

Insectivores make up 70% of bat species and locate their prey by means of echolocation. Of the remainder, most feed on fruits. Only three species sustain themselves with blood.

 

Some species even prey on vertebrates. The leaf-nosed bats (Phyllostomidae) of Central America and South America, and the two bulldog bat (Noctilionidae) species feed on fish. At least two species of bat are known to feed on other bats: the spectral bat, also known as the American false vampire bat, and the ghost bat of Australia. One species, the greater noctule bat, catches and eats small birds in the air.

 

Predators of bats include bat hawks, bat falcons and even spiders.

 

REPRODUCTION

Most bats have a breeding season, which is in the spring for species living in a temperate climate. Bats may have one to three litters in a season, depending on the species and on environmental conditions, such as the availability of food and roost sites. Females generally have one offspring at a time, which could be a result of the mother's need to fly to feed while pregnant. Female bats nurse their young until they are nearly adult size, because a young bat cannot forage on its own until its wings are fully developed.

 

Female bats use a variety of strategies to control the timing of pregnancy and the birth of young, to make delivery coincide with maximum food ability and other ecological factors. Females of some species have delayed fertilization, in which sperm is stored in the reproductive tract for several months after mating. In many such cases, mating occurs in the fall, and fertilization does not occur until the following spring. Other species exhibit delayed implantation, in which the egg is fertilized after mating, but remains free in the reproductive tract until external conditions become favorable for giving birth and caring for the offspring.

 

In yet another strategy, fertilization and implantation both occur, but development of the fetus is delayed until favorable conditions prevail, during the delayed development the mother still gives the fertilized egg nutrients, and oxygenated blood to keep it alive. However, this process can go for a long period of time, because of the advanced gas exchange system. All of these adaptations result in the pup being born during a time of high local production of fruit or insects.

 

At birth, the wings are too small to be used for flight. Young microbats become independent at the age of six to eight weeks, while megabats do not until they are four months old.

 

LIFE EXPECTANCY

A single bat can live over 20 years, but bat population growth is limited by the slow birth rate. Five species have been recorded living over 30 years in the wild: the brown long-eared bat (Plecotus auritus), little brown bat (Myotis lucifugus), Brandt's bat (Myotis brandti), lesser mouse-eared bat (Myotis blythii) and greater horseshoe bat (Rhinolophus ferrumequinum).

 

HUNTING, FEEDING AND DRINKING

Newborn bats feed solely on their mother's milk. When they are a few weeks old, bats are expected to fly and hunt on their own. It is up to them to find and catch their prey, along with satisfying their thirst.

 

To survive hibernation months, some species build up large reserves of body fat, both as fuel and as insulation.

 

HUNTING

Most bats are nocturnal creatures. Their daylight hours are spent grooming and sleeping; they hunt during the night. The means by which bats navigate while finding and catching their prey in the dark was unknown until the 1790s, when Lazzaro Spallanzani conducted a series of experiments on a group of hooded and surgically blinded bats. These bats were placed in a room in total darkness, with silk threads strung across the room. Even then, the bats were able to navigate their way through the room. Spallanzani concluded the bats were not using their eyes to fly through complete darkness, but something else.

 

Spallanzani decided the bats were able to catch and find their prey through the use of their ears. To prove this theory, Spallanzani plugged the ears of the bats in his experiment. To his pleasure, he found that the bats with plugged ears were not able to fly with the same amount of skill and precision as they were able to without their ears plugged. Unfortunately for Spallanzani, the twin concepts of sound waves and acoustics would not be understood for another century and he could not explain why specifically the bats were crashing into walls and the threads that he'd strung up around the room, and because of the methodology Spallanzani used, many of his test subjects died.

 

It was thus well known through the nineteenth century that the chiropteran ability to navigate had something to do with hearing, but how they accomplish this was not proven conclusively until the 1930s, by Donald R. Griffin, a biology student at Harvard University. Using a locally native species, the little brown bat, he discovered that bats use echolocation to locate and catch their prey. When bats fly, they produce a constant stream of high-pitched sounds. When the sound waves produced by these sounds hit an insect or other animal, the echoes bounce back to the bat, and guide them to the source.

 

FEEDING AND DIET

The majority of food consumed by bats includes insects, fruits and flower nectar, vertebrates and blood. Almost three-fourths of the world's bats are insect eaters. Bats consume both aerial and ground-dwelling insects. Each bat is typically able to consume one-third of its body weight in insects each night, and several hundred insects in a few hours. This means that a group of a thousand bats could eat four tons of insects each year. If bats were to become extinct, it has been calculated that the insect population would reach an alarmingly high number.

 

VITAMIN C

The Chiroptera as a whole are in the process of losing the ability to synthesize vitamin C: most have lost it completely. In a test of 34 bat species from six major families of bats, including major insect- and fruit-eating bat families, all were found to have lost the ability to synthesize it, and this loss may derive from a common bat ancestor, as a single mutation. However, recent results show that there are at least two species of bat, the frugivorous bat (Rousettus leschenaultii) and insectivorous bat (Hipposideros armiger), that have retained their ability to produce vitamin C.

 

AERIAL INSECTTIVORES

Watching a bat catch and eat an insect is difficult. The action is so fast that all one sees is a bat rapidly changing directions, and continuing on its way. Scientist Frederick A. Webster discovered how bats catch their prey. In 1960, Webster developed a high-speed camera that was able to take one thousand pictures per second. These photos revealed the fast and precise way in which bats catch insects. Occasionally, a bat will catch an insect in mid-air with its mouth, and eat it in the air. However, more often than not, a bat will use its tail membrane or wings to scoop up the insect and trap it in a sort of "bug net". Then, the bat will take the insect back to its roost. There, the bat will proceed to eat said insect, often using its tail membrane as a kind of napkin, to prevent its meal from falling to the ground. One common insect prey is Helicoverpa zea, a moth that causes major agricultural damage.

 

FORAGE GLEANERS

These bats typically fly down and grasp their prey off the ground with their teeth, and take it to a nearby perch to eat it. Generally, these bats do not use echolocation to locate their prey. Instead, they rely on the sounds produced by the insects. Some make unique sounds, and almost all make some noise while moving through the environment.

 

FRUITS AND FLOWER NECTAR

Fruit eating, or frugivory, is found in particular species from both major suborders. These bats favor fleshy and sweet fruits, but not those particularly strong smelling or colorful. They pull the fruit off the trees with their teeth, then fly back to their roosts to consume them, sucking out the juice and spitting the seeds and pulp out onto the ground.

 

This helps disperse the seeds of these fruit trees, which may take root and grow where the bats have left them. Over 150 types of plants depend on bats in order to reproduce.

 

Some Chiropterans consume nectar instead, for which they have acquired specialized adaptations. These bats possess long muzzles and long, extensible tongues covered in fine bristles that aid them in feeding on particular flowers and plants. However, because of these features, nectar-feeding bats cannot easily turn to other food sources in times of scarcity, making them more prone to extinction than any other type of bat.

 

Nectar feeding also aids a variety of plants, since these bats serve as pollinators: pollen gets stuck to the bats' fur while they sip the nectar, and is transferred to the next flower they visit (or dusts off in flight). Rainforests are said to benefit the most from bat pollination, because of the large variety of plants that depend on it.

 

VERTEBRATES

Some bats are primarily carnivorous, feeding on vertebrates. These bats typically eat a variety of animals, especially frogs, lizards, birds, and sometimes other bats.

 

Trachops cirrhosus, for example, is particularly skilled at catching frogs. These bats locate large groups of frogs by tracking their mating calls, then plucking them from the surface of the water with their sharp canine teeth. Another example is the greater noctule bat, which is believed to catch birds in flight.

 

Also, several bat species, found on all continents, feed on fish. They use echolocation to detect tiny ripples on the water's surface, swoop down and use specially enlarged claws on their hind feet to grab the fish, then take their prey to a feeding roost and consume it.

 

BLOOD

A few species, specifically the common, white-winged, and hairy-legged vampire bats, exclusively consume animal blood. This is referred to as hematophagy. The common vampire bat typically feeds on mammals, while the hairy-legged and white-winged vampires feed on birds instead. These species are found throughout Central and South America, as well as in Mexico and on the island of Trinidad.

 

DEFECATION

Bat dung, or guano, is so rich in nutrients that it is mined from caves, bagged, and used by farmers to fertilize their crops. During the U.S. Civil War, guano was used to make gunpowder.

 

DRINKING

In 1960, Frederic A. Webster discovered some bats' method of drinking water using a high-speed (1000 FPS) camera and flashgun. He captured one skimming just above the surface of the water, lowering its jaw to collect a small quantity of water on each pass, taking repeated passes until it drank its fill.

 

Other bats, such as the flying fox or fruit bat, gently skim the water's surface, then land nearby to lick the water from their chest fur.

 

INTERACTION WITH HUMANS

DISEASE TRANSMISSION

Bats are natural reservoirs for a large number of zoonotic pathogens, including rabies, histoplasmosis (directly and in guano), Henipavirus (i.e. Nipah virus and Hendra virus) and possibly ebola virus.

 

Their high mobility, broad distribution, long life spans, substantial sympatry, and social behaviour (communal roosting and fission-fusion social structure) make bats favourable hosts and vectors of disease. Compared to rodents, bats carry more zoonotic viruses per species, and each virus is shared with more (especially sympatric) species. They also seem to be highly resistant to many of the pathogens they carry, suggesting a potential commensal/mutualistic relationship or specific adaptations to the bats' immune systems. Furthermore, their interactions with humans' livestock and pets (e.g. cattle, pigs, goats), such as predation (in the case of vampire bats), an accidental encounter, or an animal scavenging a bat carcass, compound the risk of zoonotic transmission.

 

Among ectoparasites, bats carry fleas and mites, as well as specific parasites called bat bugs. However, they are one of the few mammalian orders that cannot host lice (most of the others are water animals). This may be due to overwhelming competition from more effective, specialized parasites, such as the bat bugs which occupy the same niche.

 

They are also implicated in the emergence of SARS (severe acute respiratory syndrome), since they serve as a natural host for the type of virus involved (the genus Coronavirus, whose members typically cause mild respiratory disease in humans). A joint CAS/CSIRO team using phylogenetic analysis found that the SARS Coronavirus originated within the SARS-like Coronavirus group carried by the bat population in China. However, note that they only served as the source of the precursor virus (which "jumped" to humans and evolved into the strain responsible for SARS): bats do not carry the SARS virus itself.

 

RABIES

As of 2016, bats present a significant hazard in areas where the virus is endemic (such as the southern United States). They serve as the natural reservoirs for the rabies virus. For example, studies performed on Mexican free-tailed bats in Austin, Texas found an exposure rate of 45% among otherwise healthy individuals.

 

In the United States, bats typically constitute around a quarter of reported cases of rabies in wild animals. However, their bites account for the vast majority of cases of rabies in humans. Of the 36 cases of domestically acquired rabies recorded in the country in 1995–2010, two were caused by dog bites and four patients were infected by receiving transplants from an organ donor who had previously died of rabies. All other cases were caused by bat bites.

 

Rabies is considered fully preventable if the patient is administered a vaccine prior to the onset of symptoms. However, unlike raccoon or skunk bites, bat bites may go ignored or unnoticed and hence untreated. Many victims may not realize they have been bitten, because bats have very small teeth and do not always leave obvious marks. Victims may also be bitten while sleeping or intoxicated, and children, pets, and the mentally handicapped are especially vulnerable. Rabid bats are broadly distributed throughout the United States; in 2008–2010, cases were reported in every state except Alaska and Hawaii, and Puerto Rico.

 

The most severe threat to humans and domestic animals comes from sick, downed, or dead bats, which typically have a very high infection rate (e.g. 70% for the Austin bats). Furthermore, since they may be clumsy, disoriented, and unable to fly, these stricken bats are much more likely to come into contact with humans.

 

Public health organizations such as the CDC generally recommend that any contact with a potentially infected animal (including any bat) be reported promptly, and those at risk of infection are treated with a post-exposure prophylaxis (PEP) regimen to prevent contraction of the virus, which is near-universally fatal with very few exceptions. 30,000 PEP treatments are performed each year in the US, in large part due to contact with bats.

 

The Centers for Disease Control and Prevention (CDC) provide fully detailed information on all aspects of bat management in North America, including how to capture a bat, what to do in case of exposure, and how to bat-proof a house humanely. In certain countries, such as the United Kingdom, it is illegal to handle bats without a license and advice should be sought from an expert organisation, such as the Bat Conservation Trust, if a trapped or injured bat is found. Where rabies is not endemic, as throughout most of Western Europe, small bats can be considered harmless. Larger bats may bite if handled.

 

There is evidence that bat rabies virus can infect victims purely through airborne transmission ("cryptic rabies"), without direct physical contact of the victim with the bat itself. This phenomenon has very rarely been reported, and has occurred among victims breathing virus-infected air in environments such as caves, after long exposures.

 

Evidence suggests that all active widespread rabies strains (i.e. those affecting most terrestrial carnivores/omnivores) evolved from strains that were originally endemic to bats. Through zoonosis, these strains mutated and "jumped" to other species. In North America, for example, this jump reportedly occurred in the mid-1600s.

 

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GNU Image Manipulation Program, commonly known by its acronym GIMP, is a free and open-source raster graphics editor used for image manipulation and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is extensible by means of plugins, and scriptable.

 

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PHILIPPINE SEA (Sep. 26, 2021) Sailors prepare an 11-meter rigid hull inflatable boat to be hoisted by a twin boom extensible crane during a training evolution in the mission bay aboard Independence-variant littoral combat ship USS Charleston (LCS 18). Charleston, part of Destroyer Squadron 7, is on a rotational deployment, operating in the U.S. 7th Fleet to enhance interoperability with partners and serve as a ready-response force in support of free and open Indo-Pacific region. (U.S. Navy photo by Mass Communication Specialist 2nd Class Ryan M. Breeden)

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Jellyfish, also known sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.

 

Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle. The medusa is normally the sexual phase, which produces planula larvae; these then disperse widely and enter a sedentary polyp phase, before reaching sexual maturity.

 

Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal group.

 

Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy.

 

They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.

 

The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.

  

Names

The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies (ctenophores, another phylum). The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word "fish" with its modern connotation of an animal with a backbone, though shellfish, cuttlefish and starfish are not vertebrates either. In scientific literature, "jelly" and "jellyfish" have been used interchangeably. Many sources refer to only scyphozoans as "true jellyfish".

 

A group of jellyfish is called a "smack" or a "smuck".

 

Definition

The term jellyfish broadly corresponds to medusae, that is, a life-cycle stage in the Medusozoa. The American evolutionary biologist Paulyn Cartwright gives the following general definition:

 

Typically, medusozoan cnidarians have a pelagic, predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked].

 

The Merriam-Webster dictionary defines jellyfish as follows:

 

A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells.

 

Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies and certain salps jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.

 

The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with on the following cladogram of the animal kingdom:

 

Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.

 

Taxonomy

The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after the polyps. Medusozoans have tetramerous symmetry, with parts in fours or multiples of four.

 

The four major classes of medusozoan Cnidaria are:

Scyphozoa are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.

Cubozoa (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.

Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. Hydrozoa show great diversity of lifestyle; some species maintain the polyp form for their entire life and do not form medusae at all (such as Hydra, which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.

Staurozoa (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle. Until recently, Staurozoa were classified within the Scyphozoa.

There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.

 

Fossil history

Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is Burgessomedusa from the mid Cambrian Burgess Shale of Canada, which is likely either a stem group of box jellyfish (Cubozoa) or Acraspeda (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent ctenophores instead.

 

Anatomy

The main feature of a true jellyfish is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea, which forms the hydrostatic skeleton of the animal. 95% or more of the mesogloea consists of water, but it also contains collagen and other fibrous proteins, as well as wandering amoebocytes which can engulf debris and bacteria. The mesogloea is bordered by the epidermis on the outside and the gastrodermis on the inside. The edge of the bell is often divided into rounded lobes known as lappets, which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia, and the margin of the bell often bears tentacles.

  

Anatomy of a scyphozoan jellyfish

On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with the mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below. The mouth opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to the exterior, perhaps supplying good oxygenation to the gonads. Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal. Cilia in these canals circulate the fluid in a regular direction.

  

Discharge mechanism of a nematocyst

The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates, allowing box jellyfish to swim faster than true jellyfish. Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia. Stalked jellyfish are attached to a solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth.

 

Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift. The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called a "nerve net" is located in the epidermis. Although traditionally thought not to have a central nervous system, nerve net concentration and ganglion-like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.

 

In many species of jellyfish, the rhopalia include ocelli, light-sensitive organs able to tell light from dark. These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into the open lagoon, where they feed, and back again.

 

Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition, supposedly making them one of the few kinds of animal to have a 360-degree view of its environment.

 

Box jellyfish eye

The study of jellyfish eye evolution is an intermediary to a better understanding of how visual systems evolved on Earth. Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization.

 

Evolution

Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that is capable of multiple task-guided behaviors.

 

Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures. Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates. The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision. Increased habitat and task complexity has favored the high-resolution visual systems common in derived cnidarians such as box jellyfish.

 

Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. Extraocular photoreception (a form of non-directional photoreception), is the most basic form of light sensitivity and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans) and other light-guided behaviors responsive to the intensity and spectrum of light. Extraocular photoreception can function additionally in positive phototaxis (in planula larvae of hydrozoans), as well as in avoiding harmful amounts of UV radiation via negative phototaxis. Directional photoreception (the ability to perceive direction of incoming light) allows for more complex phototactic responses to light, and likely evolved by means of membrane stacking. The resulting behavioral responses can range from guided spawning events timed by moonlight to shadow responses for potential predator avoidance. Light-guided behaviors are observed in numerous scyphozoans including the common moon jelly, Aurelia aurita, which migrates in response to changes in ambient light and solar position even though they lack proper eyes.

 

The low-resolution visual system of box jellyfish is more derived than directional photoreception, and thus box jellyfish vision represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and spatial resolution. This is different from the high-resolution vision that is observed in camera or compound eyes of vertebrates and cephalopods that rely on focusing optics. Critically, the visual systems of box jellyfish are responsible for guiding multiple tasks or behaviors in contrast to less derived visual systems in other jellyfish that guide single behavioral functions. These behaviors include phototaxis based on sunlight (positive) or shadows (negative), obstacle avoidance, and control of swim-pulse rate.

 

Box jellyfish possess "proper eyes" (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot. In fact, they are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision. However, the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability. The lack of the ability to focus is due to the focal length exceeding the distance to the retina, thus generating unfocused images and limiting spatial resolution. The visual system is still sufficient for box jellyfish to produce an image to help with tasks such as object avoidance.

 

Utility as a model organism

Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses. The comparison of these attributes to more derived visual systems can allow for a further understanding of how the evolution of more derived visual systems may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.

 

Characteristics

Box jellyfish visual systems are both diverse and complex, comprising multiple photosystems. There is likely considerable variation in visual properties between species of box jellyfish given the significant inter-species morphological and physiological variation. Eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology across species of box jellyfish.

 

Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories. These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes. The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation. The larger of the complex eyes contains a cellular cornea created by a mono ciliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.

 

Box jellyfish have multiple photosystems that comprise different sets of eyes. Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes photosystems that work collectively to control visually guided behaviors.

 

Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo phototransduction cascades (process of light absorption by photoreceptors) that are triggered by c-opsins. Available opsin sequences suggest that there are two types of opsins possessed by all cnidarians including an ancient phylogenetic opsin, and a sister ciliary opsin to the c-opsins group. Box jellyfish could have both ciliary and cnidops (cnidarian opsins), which is something not previously believed to appear in the same retina. Nevertheless, it is not entirely evident whether cnidarians possess multiple opsins that are capable of having distinctive spectral sensitivities.

 

Comparison with other organisms

Comparative research on genetic and molecular makeup of box jellyfishes' eyes versus more derived eyes seen in vertebrates and cephalopods focuses on: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.

 

Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes. Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts. These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has led to the conclusion that PaxB was a primordial gene in eye evolution, and that the eyes of all organisms likely share a common ancestor.

 

The lens structure of box jellyfish appears very similar to those of other organisms, but the crystallins are distinct in both function and appearance. Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses. This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms' lenses exhibit.

 

All four of the visual systems of box jellyfish species investigated with detail (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora) have invaginated synapses, but only in the upper and lower lensed eyes. Different densities were found between the upper and lower lenses, and between species. Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.

 

Evolution as a response to natural stimuli

The primary adaptive responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness. Interestingly, some box jellyfish species' eyes appear to have evolved more focused vision in response to their habitat.

 

Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches across three species of box jellyfish (Chironex fleckeri, Chiropsella bronzie, and Carukia barnesi). Behavioral studies suggest that faster pupil contraction rates allow for greater object avoidance, and in fact, species with more complex habitats exhibit faster rates. Ch. bronzie inhabit shallow beach fronts that have low visibility and very few obstacles, thus, faster pupil contraction in response to objects in their environment is not important. Ca. barnesi and Ch. fleckeri are found in more three-dimensionally complex environments like mangroves with an abundance of natural obstacles, where faster pupil contraction is more adaptive. Behavioral studies support the idea that faster pupillary contraction rates assist with obstacle avoidance as well as depth adjustments in response to differing light intensities.

 

Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This relates to the pupil's response to shifts between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function. The lower lens-eyes contain pigmented photoreceptors and long pigment cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eyes play a concentrated role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon). The upper lens of Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora (a box jellyfish species that tends to live in mangroves) does. The ability to use light to visually guide behavior is not of as much importance to Ch. bronzie as it is to species in more obstacle-filled environments. Differences in visually guided behavior serve as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.

 

Largest and smallest

Jellyfish range from about one millimeter in bell height and diameter, to nearly 2 metres (6+1⁄2 ft) in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.

 

The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 millimetres (1⁄32 in) to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools; many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope. They can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps; some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months. The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter.

 

The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m (119 ft 9 in) long (though most are nowhere near that large). They have a moderately painful, but rarely fatal, sting. The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found in some, but not all years in the waters of Japan, Korea and China in summer and autumn is another candidate for "largest jellyfish", in terms of diameter and weight, since the largest Nomura's jellyfish in late autumn can reach 2 m (6 ft 7 in) in bell (body) diameter and about 200 kg (440 lb) in weight, with average specimens frequently reaching 0.9 m (2 ft 11 in) in bell diameter and about 150 kg (330 lb) in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the Lion's Mane, whose bell diameter can reach 1 m (3 ft 3 in).

 

The rarely encountered deep-sea jellyfish Stygiomedusa gigantea is another candidate for "largest jellyfish", with its thick, massive bell up to 100 cm (3 ft 3 in) wide, and four thick, "strap-like" oral arms extending up to 6 m (19+1⁄2 ft) in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.

 

Desmonema glaciale, which lives in the Antarctic region, can reach a very large size (several meters). Purple-striped jelly (Chrysaora colorata) can also be extremely long (up to 15 feet).

 

Life history and behavior

Life cycle

Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae and then transform into adult medusae. In some species certain stages may be skipped.

 

Upon reaching adult size, jellyfish spawn regularly if there is a sufficient supply of food. In most species, spawning is controlled by light, with all individuals spawning at about the same time of day; in many instances this is at dawn or dusk. Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. In a few species, the sperm swim into the female's mouth, fertilizing the eggs within her body, where they remain during early development stages. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.

 

The planula is a small larva covered with cilia. When sufficiently developed, it settles onto a firm surface and develops into a polyp. The polyp generally consists of a small stalk topped by a mouth that is ringed by upward-facing tentacles. The polyps resemble those of closely related anthozoans, such as sea anemones and corals. The jellyfish polyp may be sessile, living on the bottom, boat hulls or other substrates, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates. Polyps may be solitary or colonial. Most polyps are only millimetres in diameter and feed continuously. The polyp stage may last for years.

 

After an interval and stimulated by seasonal or hormonal changes, the polyp may begin reproducing asexually by budding and, in the Scyphozoa, is called a segmenting polyp, or a scyphistoma. Budding produces more scyphistomae and also ephyrae. Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae. In a process known as strobilation, the polyp's tentacles are reabsorbed and the body starts to narrow, forming transverse constrictions, in several places near the upper extremity of the polyp. These deepen as the constriction sites migrate down the body, and separate segments known as ephyra detach. These are free-swimming precursors of the adult medusa stage, which is the life stage that is typically identified as a jellyfish. The ephyrae, usually only a millimeter or two across initially, swim away from the polyp and grow. Limnomedusae polyps can asexually produce a creeping frustule larval form, which crawls away before developing into another polyp. A few species can produce new medusae by budding directly from the medusan stage. Some hydromedusae reproduce by fission.

 

Lifespan

Little is known of the life histories of many jellyfish as the places on the seabed where the benthic forms of those species live have not been found. However, an asexually reproducing strobila form can sometimes live for several years, producing new medusae (ephyra larvae) each year.

 

An unusual species, Turritopsis dohrnii, formerly classified as Turritopsis nutricula, might be effectively immortal because of its ability under certain circumstances to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other organism. So far this reversal has been observed only in the laboratory.

 

Locomotion

Jellyfish locomotion is highly efficient. Muscles in the jellylike bell contract, setting up a start vortex and propelling the animal. When the contraction ends, the bell recoils elastically, creating a stop vortex with no extra energy input.

Using the moon jelly Aurelia aurita as an example, jellyfish have been shown to be the most energy-efficient swimmers of all animals. They move through the water by radially expanding and contracting their bell-shaped bodies to push water behind them. They pause between the contraction and expansion phases to create two vortex rings. Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction. Meanwhile, the second vortex ring starts to spin faster, sucking water into the bell and pushing against the centre of the body, giving a secondary and "free" boost forward. The mechanism, called passive energy recapture, only works in relatively small jellyfish moving at low speeds, allowing the animal to travel 30 percent farther on each swimming cycle. Jellyfish achieved a 48 percent lower cost of transport (food and oxygen intake versus energy spent in movement) than other animals in similar studies. One reason for this is that most of the gelatinous tissue of the bell is inactive, using no energy during swimming.

 

Ecology

Diet

Jellyfish are, like other cnidarians, generally carnivorous (or parasitic), feeding on planktonic organisms, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and voiding undigested waste through the mouth. They hunt passively using their tentacles as drift lines, or sink through the water with their tentacles spread widely; the tentacles, which contain nematocysts to stun or kill the prey, may then flex to help bring it to the mouth. Their swimming technique also helps them to capture prey; when their bell expands it sucks in water which brings more potential prey within reach of the tentacles.

 

A few species such as Aglaura hemistoma are omnivorous, feeding on microplankton which is a mixture of zooplankton and phytoplankton (microscopic plants) such as dinoflagellates. Others harbour mutualistic algae (Zooxanthellae) in their tissues; the spotted jellyfish (Mastigias papua) is typical of these, deriving part of its nutrition from the products of photosynthesis, and part from captured zooplankton. The upside-down jellyfish (Cassiopea andromeda) also has a symbiotic relationship with microalgae, but captures tiny animals to supplement their diet. This is done by releasing tiny balls of living cells composed of mesoglea. These use cilia to drive them through water and stinging cells which stun the prey. The blobs also seems to have digestive capabilities.

 

Predation

Other species of jellyfish are among the most common and important jellyfish predators. Sea anemones may eat jellyfish that drift into their range. Other predators include tunas, sharks, swordfish, sea turtles and penguins. Jellyfish washed up on the beach are consumed by foxes, other terrestrial mammals and birds. In general however, few animals prey on jellyfish; they can broadly be considered to be top predators in the food chain. Once jellyfish have become dominant in an ecosystem, for example through overfishing which removes predators of jellyfish larvae, there may be no obvious way for the previous balance to be restored: they eat fish eggs and juvenile fish, and compete with fish for food, preventing fish stocks from recovering.

 

Symbiosis

Some small fish are immune to the stings of the jellyfish and live among the tentacles, serving as bait in a fish trap; they are safe from potential predators and are able to share the fish caught by the jellyfish. The cannonball jellyfish has a symbiotic relationship with ten different species of fish, and with the longnose spider crab, which lives inside the bell, sharing the jellyfish's food and nibbling its tissues.

 

Main article: Jellyfish bloom

Jellyfish form large masses or blooms in certain environmental conditions of ocean currents, nutrients, sunshine, temperature, season, prey availability, reduced predation and oxygen concentration. Currents collect jellyfish together, especially in years with unusually high populations. Jellyfish can detect marine currents and swim against the current to congregate in blooms. Jellyfish are better able to survive in nutrient-rich, oxygen-poor water than competitors, and thus can feast on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are able to survive in warmer waters. Increased nutrients from agricultural or urban runoff with nutrients including nitrogen and phosphorus compounds increase the growth of phytoplankton, causing eutrophication and algal blooms. When the phytoplankton die, they may create dead zones, so-called because they are hypoxic (low in oxygen). This in turn kills fish and other animals, but not jellyfish, allowing them to bloom. Jellyfish populations may be expanding globally as a result of land runoff and overfishing of their natural predators. Jellyfish are well placed to benefit from disturbance of marine ecosystems. They reproduce rapidly; they prey upon many species, while few species prey on them; and they feed via touch rather than visually, so they can feed effectively at night and in turbid waters. It may be difficult for fish stocks to re-establish themselves in marine ecosystems once they have become dominated by jellyfish, because jellyfish feed on plankton, which includes fish eggs and larvae.

 

As suspected at the turn of this century, jellyfish blooms are increasing in frequency. Between 2013 and 2020 the Mediterranean Science Commission monitored on a weekly basis the frequency of such outbreaks in coastal waters from Morocco to the Black Sea, revealing a relatively high frequency of these blooms nearly all year round, with peaks observed from March to July and often again in the autumn. The blooms are caused by different jellyfish species, depending on their localisation within the Basin: one observes a clear dominance of Pelagia noctiluca and Velella velella outbreaks in the western Mediterranean, of Rhizostoma pulmo and Rhopilema nomadica outbreaks in the eastern Mediterranean, and of Aurelia aurita and Mnemiopsis leidyi outbreaks in the Black Sea.

 

Some jellyfish populations that have shown clear increases in the past few decades are invasive species, newly arrived from other habitats: examples include the Black Sea, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil).

 

Jellyfish blooms can have significant impact on community structure. Some carnivorous jellyfish species prey on zooplankton while others graze on primary producers. Reductions in zooplankton and ichthyoplankton due to a jellyfish bloom can ripple through the trophic levels. High-density jellyfish populations can outcompete other predators and reduce fish recruitment. Increased grazing on primary producers by jellyfish can also interrupt energy transfer to higher trophic levels.

 

During blooms, jellyfish significantly alter the nutrient availability in their environment. Blooms require large amounts of available organic nutrients in the water column to grow, limiting availability for other organisms. Some jellyfish have a symbiotic relationship with single-celled dinoflagellates, allowing them to assimilate inorganic carbon, phosphorus, and nitrogen creating competition for phytoplankton. Their large biomass makes them an important source of dissolved and particulate organic matter for microbial communities through excretion, mucus production, and decomposition. The microbes break down the organic matter into inorganic ammonium and phosphate. However, the low carbon availability shifts the process from production to respiration creating low oxygen areas making the dissolved inorganic nitrogen and phosphorus largely unavailable for primary production.

 

These blooms have very real impacts on industries. Jellyfish can outcompete fish by utilizing open niches in over-fished fisheries. Catch of jellyfish can strain fishing gear and lead to expenses relating to damaged gear. Power plants have been shut down due to jellyfish blocking the flow of cooling water. Blooms have also been harmful for tourism, causing a rise in stings and sometimes the closure of beaches.

 

Jellyfish form a component of jelly-falls, events where gelatinous zooplankton fall to the seafloor, providing food for the benthic organisms there. In temperate and subpolar regions, jelly-falls usually follow immediately after a bloom.

 

Habitats

Most jellyfish are marine animals, although a few hydromedusae inhabit freshwater. The best known freshwater example is the cosmopolitan hydrozoan jellyfish, Craspedacusta sowerbii. It is less than an inch (2.5 cm) in diameter, colorless and does not sting. Some jellyfish populations have become restricted to coastal saltwater lakes, such as Jellyfish Lake in Palau. Jellyfish Lake is a marine lake where millions of golden jellyfish (Mastigias spp.) migrate horizontally across the lake daily.

 

Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered benthic. The upside-down jellyfish in the genus Cassiopea typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom.

 

Some species explicitly adapt to tidal flux. In Roscoe Bay, jellyfish ride the current at ebb tide until they hit a gravel bar, and then descend below the current. They remain in still waters until the tide rises, ascending and allowing it to sweep them back into the bay. They also actively avoid fresh water from mountain snowmelt, diving until they find enough salt.

  

Parasites

Jellyfish are hosts to a wide variety of parasitic organisms. They act as intermediate hosts of endoparasitic helminths, with the infection being transferred to the definitive host fish after predation. Some digenean trematodes, especially species in the family Lepocreadiidae, use jellyfish as their second intermediate hosts. Fish become infected by the trematodes when they feed on infected jellyfish.

 

Relation to humans

Jellyfish have long been eaten in some parts of the world. Fisheries have begun harvesting the American cannonball jellyfish, Stomolophus meleagris, along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.

 

Jellyfish are also harvested for their collagen, which is being investigated for use in a variety of applications including the treatment of rheumatoid arthritis.

 

Aquaculture and fisheries of other species often suffer severe losses – and so losses of productivity – due to jellyfish.

 

Products

Main article: Jellyfish as food

In some countries, including China, Japan, and Korea, jellyfish are a delicacy. The jellyfish is dried to prevent spoiling. Only some 12 species of scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food, mostly in southeast Asia. Rhizostomes, especially Rhopilema esculentum in China (海蜇 hǎizhé, 'sea stingers') and Stomolophus meleagris (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.

 

Traditional processing methods, carried out by a jellyfish master, involve a 20- to 40-day multi-phase procedure in which, after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed. Processing makes the jellyfish drier and more acidic, producing a crisp texture. Jellyfish prepared this way retain 7–10% of their original weight, and the processed product consists of approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.

 

In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.

 

Biotechnology

The hydromedusa Aequorea victoria was the source of green fluorescent protein, studied for its role in bioluminescence and later for use as a marker in genetic engineering.

Pliny the Elder reported in his Natural History that the slime of the jellyfish "Pulmo marinus" produced light when rubbed on a walking stick.

 

In 1961, Osamu Shimomura extracted green fluorescent protein (GFP) and another bioluminescent protein, called aequorin, from the large and abundant hydromedusa Aequorea victoria, while studying photoproteins that cause bioluminescence in this species. Three decades later, Douglas Prasher sequenced and cloned the gene for GFP. Martin Chalfie figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien later chemically manipulated GFP to produce other fluorescent colors to use as markers. In 2008, Shimomura, Chalfie and Tsien won the Nobel Prize in Chemistry for their work with GFP. Man-made GFP became widely used as a fluorescent tag to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. The fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene turns on in the same tissues and the same time as the normal gene, making a fusion of the normal protein with GFP attached to the end, illuminating the animal or cell reveals what tissues express that protein—or at what stage of development. The fluorescence shows where the gene is expressed.

 

Aquarium display

Jellyfish are displayed in many public aquariums. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible. Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits as in the Monterey Bay Aquarium feature precise water flows, typically in circular tanks to avoid trapping specimens in corners. The outflow is spread out over a large surface area and the inflow enters as a sheet of water in front of the outflow, so the jellyfish do not get sucked into it. As of 2009, jellyfish were becoming popular in home aquariums, where they require similar equipment.

 

Stings

Jellyfish are armed with nematocysts, a type of specialized stinging cell. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, but only some species' venom causes an adverse reaction in humans. In a study published in Communications Biology, researchers found a jellyfish species called Cassiopea xamachana which when triggered will release tiny balls of cells that swim around the jellyfish stinging everything in their path. Researchers described these as "self-propelling microscopic grenades" and named them cassiosomes.

 

The effects of stings range from mild discomfort to extreme pain and death. Most jellyfish stings are not deadly, but stings of some box jellyfish (Irukandji jellyfish), such as the sea wasp, can be deadly. Stings may cause anaphylaxis (a form of shock), which can be fatal. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava.

 

Vinegar (3–10% aqueous acetic acid) may help with box jellyfish stings but not the stings of the Portuguese man o' war. Clearing the area of jelly and tentacles reduces nematocyst firing. Scraping the affected skin, such as with the edge of a credit card, may remove remaining nematocysts. Once the skin has been cleaned of nematocysts, hydrocortisone cream applied locally reduces pain and inflammation. Antihistamines may help to control itching. Immunobased antivenins are used for serious box jellyfish stings.

 

In Elba Island and Corsica dittrichia viscosa is now used by residents and tourists to heal stings from jellyfish, bees and wasps pressing fresh leaves on the skin with quick results.

 

Mechanical issues

Jellyfish in large quantities can fill and split fishing nets and crush captured fish. They can clog cooling equipment, having disabled power stations in several countries; jellyfish caused a cascading blackout in the Philippines in 1999, as well as damaging the Diablo Canyon Power Plant in California in 2008. They can also stop desalination plants and ships' engines.

Imbrium Lunokhod Industries Model VS-MU-333 'Lorikeet' is the next step in Imbrium Lunokhod Industries Frame System. This mass produced frame builds on the versatile and flexible mobile frame platform made popular by the VS-M/S-71 'Degei' (flic.kr/s/aHsm37uTTm) and the VS-MX-04 'Rangi' (flic.kr/s/aHsk4AUkEY). Developed for planetary surface operations and utility deployments, the Lorikeet will definitely not excel in zero-g environments, it's outclassed by more maneuverable specialty frames. But for deployments to planetary surfaces, the frame offers a more affordable (although less durable) alternative to the Varuna (flic.kr/s/aHsm89p5MW) the a more extensible (and repairable) alternative to the Krivlyaka (flic.kr/s/aHsm4d6e2v).

 

From a design perspective, the frame takes a ton of inspiration from both Malcolm Craig's MgN-333 (flic.kr/p/dEFocc) and Aardvark17's Budgie (flic.kr/p/2kgyyua) frames as well as my version of the HR-13 flic.kr/s/aHsmMLcB3m.

 

===========================================================

Built for Mobile Frame Zero - a tabletop wargame.

Mobile Frame Hangar Nova (MFZ Community Forums).

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How can a rocket engine that generates 5,000 degree steam and 13,000 lbs of thrust form icicles, too!

 

It's cryogenic.

 

The Common Extensible Cryogenic Engine, CECE for short, based on the design of the heritage Pratt & Whitney Rocketdyne RL10 engine, has completed its third round of intensive testing. This technology development engine is fueled by a mixture of minus 297F liquid oxygen and minus 423F liquid hydrogen. The engine components are super-cooled to similar low temperatures. As the CECE burns its frigid fuels, gas composed of hot steam is produced and propelled out the nozzle creating thrust. This high speed, hot gas mixture is essential for propulsion. The steam is cooled by the cold engine nozzle, condensing and eventually freezing at the nozzle exit to form icicles. Using liquid hydrogen and oxygen in rockets will provide major advantages for landing astronauts on the moon. Hydrogen is very light but enables about 40 percent greater performance (force on the rocket per pound of propellant) than other rocket fuels. Therefore, NASA can use this weight savings to bring a bigger spacecraft with a greater payload to the moon than with the same amount of conventional propellants. CECE is a step forward in NASA's efforts to develop reliable, robust technologies to return to the moon -- and a winter wonder.

 

Image Credit:

Pratt & Whitney Rocketdyne

 

View larger image:

www.nasa.gov/mission_pages/constellation/multimedia/cece....

 

You can also go here to read more about the image and see a streaming Windows movie of the rocket test:

www.nasa.gov/mission_pages/constellation/news/cece.html

   

A small slow-moving lizard with a long extensible tongue and tail.It has protruding eyes that rotate independently, and has the ability to change body colour hence the name 'Chameleon' I always thought a chameleon changed colour to hide but have just recently found out it's in fact the way that they communicate with each other.

Foreword

 

First of all, a deep (and entirely unoriginal) apology for being inactive for so long. Just after last Christmas, I was hit in the face by a huge flaming chunk of Real Life, leaving virtually zero time for my pet projects. I have still been answering emails sent to kaelri+lcd@gmail.com, so if you have a question, or you need help with Enigma, please don't hesitate to send a message. I still can't guarantee a prompt reply, but it's your best bet, and it's always great to hear from people.

 

Since it's been so long, I wanted to reward your patience with a real in-depth post. With screenshots! So read on.

 

Although I've had no opportunity to work on Rainmeter stuff, I've used some of my scattered moments of free time to tweak my Firefox setup, based on experiences with Chrome, Opera, and yes, even Safari 5. The beauty of extensible browsers is that whenever one of them gets a great new feature, someone will make it available for the others in short order. This means that the most extensible, customizable browser gets a huge Darwinian advantage. And in that, Firefox is still the undisputed king.

 

-----------------------

 

Chrome

 

Even though I've made a lot of behind-the-scenes changes, you'll notice that it doesn't look much different from my previous setup from almost two years ago. That's because I can't really simplify it any more than it is. I've even removed the back/forward and menu buttons now, so typically, the only element that's actually visible is the awesomebar on top.

 

Theme: After all this time, NASA Night Launch is still the best, cleanest, smoothest, most professional dark-colored Firefox theme on the planet. If they charged for this theme, I would pay.

 

Search: I really feel that keyword-based search bookmarks are the perfect solution to this issue of combining the search and address bars. I could never get the hang of Chrome's way of doing things - if I type "wiki lifehacker," will I search Wikipedia for "lifehacker," or will I google for "wiki lifehacker"? An action that is so basic to modern Internet living requires a method as habitual and thought-free as possible, and keywords are the answer. All I have to do is prefix whatever I type with the corresponding code:

- g: Google

- w: Wikipedia

- u: YouTube

- d: Dictionary.com

- t: Thesaurus.com

- tr: Google Translate (This will automatically translate the text which follows.)

To set this up for yourself, copy the link location of each search into a bookmark, and type the desired prefix into the "keyword" field. Thanks again to Nabeel for introducing me to this concept.

 

[Screenshot]

 

Menu: You'll notice that there's absolutely no menu bar or button in sight. That's because I'm using a feature of Personal Menu that I've previously overlooked: adding menu items to the toolbar context menu. I can now just right-click on either side of my toolbar to access the menu. I know it sounds awkward, but it's actually very easy to get used to. I use keyboard shortcuts for most things, which allowed me to condense everything I actually use into a remarkably short list.

 

[Screenshot]

 

Status Bar: Gone, obviously, but replaced with the simplest, most perfect extension I've ever seen. It's called Fission, and it does exactly three things. First, it adds a loading bar to the background of the awesomebar, ala Safari. (You can also have it normal-sized on the far-right side, which I do, because otherwise it's wasted space.) Second, it displays the page status, also on the far right side. Third, when you hover over a link, it changes the address in the awesomebar to the location of the link. In other words, it uses the awesomebar to completely replace all the usefulness of the status bar, and it does so in the most elegant way imaginable.

 

[Screenshot]

 

-----------------------

 

Sidebar

 

I think the most dramatic addition is the sidebar, courtesy of All-in-One Sidebar. I gave Opera another try several weeks ago, and while I ultimately switched back to Firefox, I was smitten with the sidebar that Opera uses. I found it easier to use, because it's adjacent to the edge of the screen, so it requires less aiming than the regular (horizontal) toolbars, and it saves vertical space, which, as we all know, is more important on a widescreen laptop. Two hours later, I'd found this, and now, my entire interface, other than the awesomebar, has been moved to it. AiOS is wonderful in several different ways:

 

Hide/Show: I probably would not have kept this extension if there hadn't been an easy way to hide it when I wanted to minimize my interface. Fortunately, it offers not only a grabber on the far left (barely visible, but easy to click, since I only need to flick the mouse left), but a keyboard shortcut: F4.

 

[Screenshot]

 

Flexible Buttons: I only have a few buttons, but as you can see, they're stretched out to fill the full height of the window. This is great, because it gives each button an absolutely gigantic click area.

 

Sidebars: This is actually the point of AiOS. As you know, Firefox can open your Bookmarks (Ctrl-B) and History (Ctrl-H) as sidebar panels. AiOS takes this further: it lets you open Downloads, Addons, Page Info, and other tools as docked, collapsible panels. It feels good to have all of Firefox's most important dialogs in a consistent format, and if you're, say, doing a lot of tweaking in your various extensions' options, it saves a lot of time to have it permanently open.

 

[Screenshot]

 

MultiPanel: AiOS adds one more sidebar of its own, called MultiPanel. This does a couple of different things. The one I love most is that you can open a second page inside the panel. It can even render the page in a mobile format, perfect for sidebar viewing. Menus at the top of the panel also offer quick access to the page source (which can be made to open in the sidebar by default) and the "about:" dialogs, including about:config (same).

 

[Screenshot (Full)]

[Screenshot (Mobile)]

 

-----------------------

 

Fast Dial

 

Still using Fast Dial as both my homepage and new-tab page. I could save on some performance by replacing it with a homemade HTML file, but for the moment, it doesn't bother me, and it's nice for the infrequent times when I do need to move stuff around. I made the thumbnails myself in Photoshop (not that they're anything special; just jumping on the Helvetica bandwagon).

 

As you can probably tell from the contents, I'm still a heavy and devoted user of Google services, especially since I've finally taken the leap to browser-only messaging. Yes, I have given up Thunderbird (except for making IMAP backups, because I'm still paranoid), and am now using Gmail to manage four different email addresses from a single inbox, which, to Gmail's credit, is working flawlessly, thanks to a combination of forwarding, filtering, and a secure send-from-address feature. As for my feeds, I'm using Google Reader with the gorgeous Helvetireader skin, via Greasemonkey. And as they say, I haven't looked back.

 

[Screenshot (Reader)]

[Screenshot (Mail)]

 

-----------------------

 

Bookmarks

 

It took a bit of fiddling, but I was able to add my bookmarks toolbar to the sidebar. Here's the trick: I moved all of my bookmarks into a single, unlabeled folder, so the effect is that it appears as if it's just a button, and therefore takes no horizontal space. The only (nitpicky) downside is that it doesn't really work without the "flexible buttons" option in AiOS; it expands to fill the entire sidebar vertically, which is annoying.

 

One of the things I'm asked about most often is my organization scheme. It's pretty simple, actually. Writer contains the sites where I'm an active member and contributor: forums, wikis, etc. Reader used to contain my daily reading material, before I started using feeds; now it holds my archive of saved posts, news stories and other pages, sorted by tag. (I discovered this completely by accident: Firefox lets you add a tag to any bookmark folder, where it appears as a menu.) Writer is where I save the pages that I don't have time to read. As you can imagine, this grows rapidly, and I have to cull it every few weeks. Resources is a list of useful tools that I may need during the course of the day. (Click the screenshot below to see.) After that, all that's left are a few folders dedicated to each of my currently-active projects. This method has served me well for literally years. I don't know if it qualifies as a "GTD" tactic, but I certainly recommend it.

 

[Screenshot (Reader)]

[Screenshot (Resources)]

 

Readability: This is the newest addition to my browsing suite. After Safari 5 popped up last week - although Safari for Windows is still the trashiest app ever released by a developer of Apple's standing - I was reasonably impressed with the "Reader" feature, and, naturally, I tried to see if anything like it was available for Firefox. Lo and behold, I discovered Readability. It's a bookmarklet which changes the layout of any page you throw at it, stripping all the unnecessary elements and reformatting the text to your preferred reading conditions. It's lovely. (Via Soeren Says.)

 

[Screenshot]

  

-----------------------

 

Gestures

 

The last extension I'll be highlighting is All-in-One Gestures. Like AiOS, I grabbed this after being really pleased with the mouse gestures in Opera. I never really thought I'd like them, but it does save an awful lot of time, and of course, it's customizable, so you can define those gestures that are most intuitive to you. It's now just a quick swipe to go back, forward, to the top or bottom of the page, to refresh, to open a new tab, or load the homepage in the current tab. These are just a few of the functions it can be used to invoke. It even has a command to increment a digit in the current page's URL - in other words, scroll through multi-page articles with a flick of the wrist. I admit, this isn't as seamless as Opera's method, which not only finds the page number automatically, but activates it whenever you use "forward" on a page that's already at the end of your history. But this works. I don't have to think about it, which is the most important thing.

 

This is also a great example of how extensions can be used to enhance each other. One of AiOG's other uses is to open a "favorite bookmark." I added the Readability bookmarklet (above). So now, I can reformat any webpage to my liking with a flick of the wrist. Welcome to the future.

 

-----------------------

 

Other Extensions

 

I won't go in-depth with these, since they're not really relevant to my browser interface like the others are. But for completion's sake, I'm also using:

- Adblock Plus

- Firefox Sync

- Lazarus Form Recovery

- Resurrect Pages

- Shooter

 

-----------------------

 

One More Thing

 

Go to about:config. Find the key called "general.smoothScroll". Change it to true. Instant smooth-scrolling, no extensions needed. Cheers.

Porte ouverte 8 mars 2014 à l'AFT-IFTIM. Monchy-Saint-Eloi (F-60).

"The hummingbird, also known as hummingbird, cuitelo, suck flower, pink-flower, suck honey, binga, Guanambi, guinumbi, guainumbi, guanumbi [1] and mainoĩ, [2] is a Trochilidae family bird, composed 108 genera and 322 known species. In Brazil, some genres are given other names, such as tails-white genre Phaethornis or straight-nozzles Heliomaster genre. In the classificatory system of Sibley & Ahlquist, the Trochilidae family was part of a proper order, the Apodiformes. Among the group's distinctive features include the elongated beak, food-based nectar, eight pairs of ribs, fourteen to fifteen cervical vertebrae, iridescent plumage and an extensible and bifurcated tongue".Fonte Wikipédia

Horned Treehopper (Membracidae)

 

Treehoppers (more precisely typical treehoppers to distinguish them from the Aetalionidae) and thorn bugs are members of the family Membracidae, a group of insects related to the cicadas and the leafhoppers. About 3,200 species of treehoppers in over 400 genera are known. They are found on all continents except Antarctica; only three species are known from Europe. Individual treehoppers usually live for only a few months.

  

Morphology

 

Thorn bugs, due to their unusual appearance, have long interested naturalists. They are best known for their enlarged and ornate pronotum, which most often resembles thorns, apparently to aid camouflage. In some species, the pronotum is a horn-like extension, but can form more bizarre shapes. The specialised pronotum (or helmet) may not be simply an expansion of the prothoracic sclerite, but a fused pair of dorsal appendages of the first thoracic segment.

 

These may be serial homologues of insect wings, which are dorsal appendages of the second and/or third thoracic segments. Evidence for this theory includes the development of the helmet, which arises as a pair of appendages attached to each side of the dorsal prothorax by an articulation with muscles and a flexible membrane that allow it to be mobile. Also, the same genes are involved in development of the helmet and the wings. Distinguishing males from females is accomplished only by looking at the genitalia.

  

Ecology

 

Treehoppers pierce plant stems with their beaks, and feed upon sap. The immatures can frequently be found on herbaceous shrubs and grasses, whereas the adults more often frequent hardwood tree species. Excess sap becomes concentrated as honeydew, which often attracts ants. Some species have a well-developed ant mutualism, and these species are normally gregarious, as well, which attracts more ants. The ants provide protection from predators. Treehoppers mimic thorns to prevent predators from spotting them.

 

Others have formed mutualisms with wasps, such as Parachartergus apicalis. Even geckos form mutualistic relations with treehoppers, with whom they communicate by small vibrations of the abdomen.

 

Eggs are laid by the female with her saw-like ovipositor in slits cut into the cambium or live tissue of stems, though some species lay eggs on top of leaves or stems. The eggs may be parasitised by wasps, such as the tiny fairyflies (Mymaridae) and Trichogrammatidae. The females of some membracid species sit over their eggs to protect them from predators and parasites, and may buzz their wings at intruders. The females of some gregarious species work together to protect each other's eggs. In at least one species, Publilia modesta, mothers serve to attract ants when nymphs are too small to produce much honeydew. Some other species make feeding slits for the nymphs.

 

Like the adults, the nymphs also feed upon sap, and unlike adults, have an extensible anal tube that appears designed to deposit honeydew away from their bodies. The tube appears to be longer in solitary species rarely attended by ants. It is important for sap-feeding bugs to dispose of honeydew, as otherwise it can become infected with sooty moulds. Indeed, one of the evident benefits of ants for Publilia concava nymphs is that the ants remove the honeydew and reduce such fungal growth.

 

Most species are innocuous to humans, although a few are considered minor pests, such as Umbonia crassicornis (a thorn bug), the three-cornered alfalfa hopper (Spissistilus festinus), and the buffalo treehopper (Stictocephala bisonia), which has been introduced to Europe. The cowbug Oxyrachis tarandus has been recorded as a pest of Withania somnifera in India.

  

Systematics

 

The diversity of treehoppers has been little researched, and their systematic arrangement is tentative. It seems three main lineages can be distinguished; the Endoiastinae are the most ancient treehoppers, still somewhat resembling cicadas. Centrotinae form the second group; they are somewhat more advanced but the pronotum still does not cover the scutellum in almost all of these. The Darninae, Heteronotinae, Membracinae and Smiliinae contain the most apomorphic treehoppers.

 

Several proposed subfamilies seem to be paraphyletic. Centronodinae and Nicomiinae might need to be merged into the Centrotinae to result in a monophyletic group.

 

[Credit: en.wikipedia.org]

www.cotech.ca

Horned Treehopper (Membracidae)

 

Treehoppers (more precisely typical treehoppers to distinguish them from the Aetalionidae) and thorn bugs are members of the family Membracidae, a group of insects related to the cicadas and the leafhoppers. About 3,200 species of treehoppers in over 400 genera are known. They are found on all continents except Antarctica; only three species are known from Europe. Individual treehoppers usually live for only a few months.

  

Morphology

 

Thorn bugs, due to their unusual appearance, have long interested naturalists. They are best known for their enlarged and ornate pronotum, which most often resembles thorns, apparently to aid camouflage. In some species, the pronotum is a horn-like extension, but can form more bizarre shapes. The specialised pronotum (or helmet) may not be simply an expansion of the prothoracic sclerite, but a fused pair of dorsal appendages of the first thoracic segment.

 

These may be serial homologues of insect wings, which are dorsal appendages of the second and/or third thoracic segments. Evidence for this theory includes the development of the helmet, which arises as a pair of appendages attached to each side of the dorsal prothorax by an articulation with muscles and a flexible membrane that allow it to be mobile. Also, the same genes are involved in development of the helmet and the wings. Distinguishing males from females is accomplished only by looking at the genitalia.

  

Ecology

 

Treehoppers pierce plant stems with their beaks, and feed upon sap. The immatures can frequently be found on herbaceous shrubs and grasses, whereas the adults more often frequent hardwood tree species. Excess sap becomes concentrated as honeydew, which often attracts ants. Some species have a well-developed ant mutualism, and these species are normally gregarious, as well, which attracts more ants. The ants provide protection from predators. Treehoppers mimic thorns to prevent predators from spotting them.

 

Others have formed mutualisms with wasps, such as Parachartergus apicalis. Even geckos form mutualistic relations with treehoppers, with whom they communicate by small vibrations of the abdomen.

 

Eggs are laid by the female with her saw-like ovipositor in slits cut into the cambium or live tissue of stems, though some species lay eggs on top of leaves or stems. The eggs may be parasitised by wasps, such as the tiny fairyflies (Mymaridae) and Trichogrammatidae. The females of some membracid species sit over their eggs to protect them from predators and parasites, and may buzz their wings at intruders. The females of some gregarious species work together to protect each other's eggs. In at least one species, Publilia modesta, mothers serve to attract ants when nymphs are too small to produce much honeydew. Some other species make feeding slits for the nymphs.

 

Like the adults, the nymphs also feed upon sap, and unlike adults, have an extensible anal tube that appears designed to deposit honeydew away from their bodies. The tube appears to be longer in solitary species rarely attended by ants. It is important for sap-feeding bugs to dispose of honeydew, as otherwise it can become infected with sooty moulds. Indeed, one of the evident benefits of ants for Publilia concava nymphs is that the ants remove the honeydew and reduce such fungal growth.

 

Most species are innocuous to humans, although a few are considered minor pests, such as Umbonia crassicornis (a thorn bug), the three-cornered alfalfa hopper (Spissistilus festinus), and the buffalo treehopper (Stictocephala bisonia), which has been introduced to Europe. The cowbug Oxyrachis tarandus has been recorded as a pest of Withania somnifera in India.

  

Systematics

 

The diversity of treehoppers has been little researched, and their systematic arrangement is tentative. It seems three main lineages can be distinguished; the Endoiastinae are the most ancient treehoppers, still somewhat resembling cicadas. Centrotinae form the second group; they are somewhat more advanced but the pronotum still does not cover the scutellum in almost all of these. The Darninae, Heteronotinae, Membracinae and Smiliinae contain the most apomorphic treehoppers.

 

Several proposed subfamilies seem to be paraphyletic. Centronodinae and Nicomiinae might need to be merged into the Centrotinae to result in a monophyletic group.

 

[Credit: en.wikipedia.org]

Laced Woodpecker (Picus vittatus)

  

The laced woodpecker (Picus vittatus) is a species of bird in the Picidae family.

It is found in Cambodia, Indonesia, Laos, Malaysia, Myanmar, Singapore, Thailand, Vietnam and perhaps Bangladesh.

 

Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist lowland forests, subtropical or tropical mangrove forests, and subtropical or tropical moist montane forests.

  

Species: Laced Woodpecker Picus vittatus *

* The generic name stems from a Latin word: picus = woodpecker. (In Roman mythology, Picus, a brave warrior, was turned into a woodpecker by Circe, whose love he rejected. Seen as the god of agriculture, with the power of prophecy, he was widely worshipped in ancient Italy and was represented as a woodpecker, an important bird in augury.) In Latin, the species name vittatus = striped or banded.

 

Other common names: Bamboo Green Woodpecker, Laced Green Woodpecker, Small Scaly-bellied Woodpecker, Small Scaly-bellied Green Woodpecker.

 

Taxonomy: Picus vittatus Vieillot 1818, Java.

 

Sub-species & Distribution: The species ranges from S China down to Myanmar, Thailand, Malaysia, Singapore, Sumatra, Java and Bali. It is not found in Borneo. It is sometimes seen as being conspecific with the Streak-breasted Woodpecker Picus viridanus. Some authors consider it to be monotypic, while others recognise three sub-forms. The nominate form is found in Singapore and peninsular Malaysia, while another race, connectens, usually considered invalid, is found on Langkawi Island only.

 

Size: 10 to 11" (25.5 to 28.0 cm). Sexes slightly differ.

 

Description: Forehead and crown red, often finely streaked with black, extending onto the nape. Lores pale buffy-brown. A black patch above the lores, extending as a thin superciliary stripe along the sides of crown, with a fine white line below it starting just above the eye. Broad black moustachial streak from the base of lower mandible to the sides of the neck. Above it, a fine white streak starting from the base of upper mandible. Lower face grey, ear coverts darker, sides of nape and upper back bright greenish-brown. Mantle bright olive, the feathers edged yellowish-green, brighter on rump and uppertail coverts. Primaries brownish-black, with regular white bands on outer webs, secondaries similar with outer webs edged with bright olive, the white bands less distinct. Wing coverts dark olive tinged with metallic bronze, edged with greenish-yellow. The pointed tail feathers, stiffened by a strong central shaft except for the shorter outer pair, are blackish-brown, with whitish bars at regular intervals. Chin, throat and breast dull brownish-olive. Belly, lower abdomen and vent dark brownish-buff, the feathers being pale centrally and broadly edged with olive on both sides, producing a heavily striped appearance.

 

Females are very similar but have the top of the head entirely black. In immature birds, the green of the upperparts is duller than in adults, the face more greyish-brown and extending to the sides of the nape. The underparts are paler, the stripes much less distinct. Nestlings of both sexes have black crowns, the young males often acquiring red on the crown while still being fed by the parents.

 

Soft parts: Iris wine-red, dark brown in young birds, eye-ring greenish-grey. Tarsus greenish-horn. Upper mandible black, sometimes marked with yellow and paler at tip, lower mandible yellow at base, darker at tip.

 

Similar species: This species very closely resembles the Streak-breasted Woodpecker Picus viridanus which is not found in Singapore but does occur in peninsular Malaysia.

 

Picus vittatus: Chin, throat and upper breast dull brownish-olive, with no streaks. Lower breast dark brownish-buff with fine lacy marks.

 

Picus viridanus: Throat greener, lightly streaked. Entire breast green, with bold scaly streaks.

 

Status, Habitat & Behaviour: A coastal species found in the casuarinas and mangrove belt from Perak down to Johore and Singapore, it is common on both sides of the Johore Straits but is rarely found inland (Robinson & Chasen 1939). While Burknill & Chasen (1927) considered it unlikely to be found in gardens or near town, the degree of forest clearance since then may have changed things somewhat.

 

Medway & Wells (1976) found it in mangrove and adjacent secondary growth to, at the most, 24 km inland in coconut plantations and village gardens. Wells (1999) found it common near the coast, less so inland, but noted its landward expansion, particularly since 1970's, into oil palm and rubber plantations, nearby wooded gardens and parkland up to 30 km from the sea, but strictly at plains level.

 

Since the early 1900's, there has been much debate, and confusion, over its taxonomy, as well as its status and relationships to very similar birds, such as the Streak-breasted Woodpecker Picus viridanus and the Streak-throated Woodpecker Picus xanthopygaeus, found in peninsular Malaya, Thailand and Myanmar. This debate still continues, and further taxonomic migration can be anticipated. As a result, very little of the early data, on its habits and behaviour, can safely be ascribed to this species.

 

Found singly, in pairs or in small family parties, it is not a shy bird. Most often, it is seen on tree trunks, its tail depressed and partly fanned out to support it against the bark, climbing upwards, often going round and round the trunk in short jerky movements, sometimes hopping backwards for a pace or two. Every now and again, it stops and, with its head cocked to one side, peers very intently at the tree bark, possibly to listen for activity beneath the bark, occasionally tapping tentatively at the bark with its bill. Whenever it suspects the presence of its prey, it starts pecking furiously away, vigorously enough to send wood chips flying all around it, then inserts its tongue into the cavity to extract food.

 

The bird frequently finds its food on the fallen trunks of trees, in tall grass, and can regularly be seen feeding on the ground, the tail pressed against the ground, the body held upright. The underparts of several museum specimens were sullied with mud, suggesting that the birds had fed on the ground or on the roots of mangrove (Burknill & Chasen 1927). In Perak, they were seen searching for food among the fallen leaves in a rubber estate (Edgar 1933). A pair was seen feeding on the ground in Singapore too (Kwong 2011).

 

Occasionally, it can be seen perched on tree trunks or stumps, sunning itself with one or both wings partly outstretched. When disturbed, it flies a short distance to land on the lower branches of a nearby tree. Its flight is strong and undulating.

 

Food: Like all woodpeckers, it feeds mainly on termites, ants and other small insects, including the larvae and eggs of wood-boring insects, hidden in decaying wood or within the hollow stems of various plants. It finds its prey by chiselling into the rotting wood. Then, using its long and greatly extensible tongue, the barbed tip covered with glutinous saliva, it probes deep into the cavity to extract the prey. In Singapore, a bird was seen on the ground, apparently eating worms (Jane 2010).

 

There is very little by way of detailed information specific to its diet but it has been known to eat fruit and berries. A congeneric species, the Streak-throated Woodpecker Picus xanthopygaeus, takes the nectar of flowers from the Erythrina and Salmalia trees, and drinks juice from date palms tapped for toddy (Ali & Ripley 1970). From Singapore, there are reports of this bird feeding at a durian tree Durio zibethinus (Goh et al 2006), and on an oil palm tree Elaeis guineensis (Chow 2011) - whether the bird was actually eating the fruit, drinking the sap or feeding on insects remains unclear. Additionally, there is an early record, from 1989, of this bird being seen "pecking and gobbling the juicy flesh of rambutans" but the actual source of this citation, however, remains elusive.

 

Voice and Calls: Its call is a high-pitched and fairly loud kek, repeated about a dozen times, every two to three seconds or so.

 

Breeding: In Singapore, nest building has been recorded from December to April and June, brooding in April and May, chicks in June, and young birds were seen in June and August (Wang & Hails 2007). In Perak, West Malaysia, nests were found from March to April (Edgar 1933). Medway & Wells (1976) have recorded nests between February and June.

 

Like all woodpeckers, it nests in holes excavated into tree trunks. Their nests, situated 1 to 9 m (3 to 30 feet) above the ground level, have been found on an "api-api' tree (Avicennia spp.), dead coconut trees Cocos nucifera, on a hog-plum tree Spondias spp, a dead mango tree Mangifera spp (Edgar 1933) and on a casuarina tree (Madoc 1956). Though it appears to nest mainly on dead trunks, some nests have been excavated into living trees (Wells 1999).

 

The normal clutch consists of four eggs, pinkish-white, fairly glossy, the average size varying from 26.4 x 19.1 mm. to 27.4 x 21.1 mm. (Edgar 1933). Both sexes help excavate the nest, incubate the eggs and feed the young. Very little is known of its courtship behaviour or its breeding biology.

 

Moult: In Genus Picidae, the primaries moult descendantly and sequentially, the secondaries from two centres, ascendantly from S1 (starting after P5), ascendantly and descendantly from S8 (starting with P3). Tail moult is centrifugal. Post-nuptial is complete. Post-juvenile moult is partial, of primaries, tail and body but not the secondaries, primary coverts or tertials though, sometimes, one or two tertials may be replaced. Occasionally, the outer primary coverts are also moulted, with contrast between the new and old feathers showing (Baker 1993).

 

On 26th August, a family party of two adults and an immature bird was caught at Ulu Pandan in Singapore. The male, with an ill-defined brood patch, was in post-nuptial moult. Wing: P1 to P4 = 5, P5 = 3, P6 = 1, rest = 0, S1 = 4, S2 to S5 = 0, S6 to S8 = 5. Tail: T1 = 0, T2 = 2, T3 = 1, rest = 0. The female, with a distinct brood patch, was also in post-nuptial moult. Wing: P1 to P3 = 5, P4 = 4, P5 = 2, rest = 0. S1 to S6 = 0, S7 to S8 = 5. Tail: T1 = 0, T2 = 1, rest = 0. The immature bird, a female, was undergoing post-juvenile moult. Wing: P1 to P2 = 5, P3 = 4, P4 = missing, rest = 0 (Wang 1999).

 

Miscellaneous: Generally speaking, birds are said to have very little sense of smell or taste. Whether woodpeckers have an acute sense of hearing which enables them to detect the movements of prey items hidden within the wood or whether tapping at the wood with the bill enables them to locate any prey in hidden hollows beneath the surface of the wood, is not entirely clear.

 

The bone structure in a woodpecker's skull is part of an evolutionary adaptation that enables it to hammer away into tree trunks without suffering damage to its brain. Its tongue, too, often more than twice the length of the bird's skull, is just as specialised. More information about this can be obtained from the ON Nature magazine, or the Wild Birds Unlimited site.

 

To discover how the development of the woodpecker's skull has helped inspire the development of shock absorbers, please visit this page published in the New Scientist. The original paper it cites, a highly technical and detailed effort, A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems (Yoon & Park 2011), can be obtained at the IOPscience website.

 

Two adult birds ringed at Rantau Panjang were recaptured there 116 and 120 months later (Medway & Wells 1976).

  

[Credit: singaporebirds.net/]

PHILIPPINE SEA (Sep. 26, 2021) Sailors guide an 11-meter rigid hull inflatable boat during a twin boom extensible crane training evolution in the mission bay aboard Independence-variant littoral combat ship USS Charleston (LCS 18). Charleston, part of Destroyer Squadron 7, is on a rotational deployment, operating in the U.S. 7th Fleet to enhance interoperability with partners and serve as a ready-response force in support of free and open Indo-Pacific region. (U.S. Navy photo by Mass Communication Specialist 2nd Class Ryan M. Breeden)

A wild tangent inspired by Dominik Strzelec's Processing demo of catenary curves in Toxiclibs.

 

I was curious about the simulation aspect and how it might relate to parametric modeling, but then I added some basic color shading and promptly forgot about everything else. Sketches like these don't really have a defined place in my current practice and I usually only get to show them in lectures, so by now I have a growing elephant graveyard of code sketches like these.

 

I'm embarrassed to say this is the first time I've seriously used Toxiclibs for more than 20 minutes. It really is a thing of beauty and contains some very powerful tools once you figure out Karsten's code structure. Most coders tend towards idiosyncracy and Karsten is no exception, but his manifests itself in the form of well-thought out and extensible code structures while mine are far less elegant.

 

I plan to post a version of my sketch on OpenProcessing as a nod to Dominik for using his code. The physical simulation is still Toxiclibs, but I've moved all rendering, GUI and meshing to Modelbuilder for my own convenience's sake.

via Modebas.fr modebas.fr/socquettes/2093-pack-de-2-paires-socquette-inv...

PACIFIC OCEAN (Sept. 21, 2020) Sailors prepare to recover an 11-meter rigid-hulled inflatable boat (RHIB) from the water while conducting twin-boom-extensible crane (TBEC) operations in the well deck of Independence-class littoral combat ship USS Gabrielle Giffords (LCS 10). Gabrielle Giffords is underway conducting routine operations in the 3rd Fleet area of operations. (U.S. Navy photo by Mass Communication Specialist 2nd Class Allen Michael Amani)

Prototype of the Mercury, an infinitely extensible, open camera system that I developed over the past two years, with some help from others. This one is shown configured to shoot medium format digital.

Prototype of the Mercury, an infinitely extensible, open camera system that I developed over the past two years, with some help from others. This one is shown with a medium format (23, or 6x9) sheet film holder with custom grooves for the Graflok back.

Laced Woodpecker (Picus vittatus)

  

The laced woodpecker (Picus vittatus) is a species of bird in the Picidae family.

It is found in Cambodia, Indonesia, Laos, Malaysia, Myanmar, Singapore, Thailand, Vietnam and perhaps Bangladesh.

 

Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist lowland forests, subtropical or tropical mangrove forests, and subtropical or tropical moist montane forests.

  

Species: Laced Woodpecker Picus vittatus *

* The generic name stems from a Latin word: picus = woodpecker. (In Roman mythology, Picus, a brave warrior, was turned into a woodpecker by Circe, whose love he rejected. Seen as the god of agriculture, with the power of prophecy, he was widely worshipped in ancient Italy and was represented as a woodpecker, an important bird in augury.) In Latin, the species name vittatus = striped or banded.

 

Other common names: Bamboo Green Woodpecker, Laced Green Woodpecker, Small Scaly-bellied Woodpecker, Small Scaly-bellied Green Woodpecker.

 

Taxonomy: Picus vittatus Vieillot 1818, Java.

 

Sub-species & Distribution: The species ranges from S China down to Myanmar, Thailand, Malaysia, Singapore, Sumatra, Java and Bali. It is not found in Borneo. It is sometimes seen as being conspecific with the Streak-breasted Woodpecker Picus viridanus. Some authors consider it to be monotypic, while others recognise three sub-forms. The nominate form is found in Singapore and peninsular Malaysia, while another race, connectens, usually considered invalid, is found on Langkawi Island only.

 

Size: 10 to 11" (25.5 to 28.0 cm). Sexes slightly differ.

 

Description: Forehead and crown red, often finely streaked with black, extending onto the nape. Lores pale buffy-brown. A black patch above the lores, extending as a thin superciliary stripe along the sides of crown, with a fine white line below it starting just above the eye. Broad black moustachial streak from the base of lower mandible to the sides of the neck. Above it, a fine white streak starting from the base of upper mandible. Lower face grey, ear coverts darker, sides of nape and upper back bright greenish-brown. Mantle bright olive, the feathers edged yellowish-green, brighter on rump and uppertail coverts. Primaries brownish-black, with regular white bands on outer webs, secondaries similar with outer webs edged with bright olive, the white bands less distinct. Wing coverts dark olive tinged with metallic bronze, edged with greenish-yellow. The pointed tail feathers, stiffened by a strong central shaft except for the shorter outer pair, are blackish-brown, with whitish bars at regular intervals. Chin, throat and breast dull brownish-olive. Belly, lower abdomen and vent dark brownish-buff, the feathers being pale centrally and broadly edged with olive on both sides, producing a heavily striped appearance.

 

Females are very similar but have the top of the head entirely black. In immature birds, the green of the upperparts is duller than in adults, the face more greyish-brown and extending to the sides of the nape. The underparts are paler, the stripes much less distinct. Nestlings of both sexes have black crowns, the young males often acquiring red on the crown while still being fed by the parents.

 

Soft parts: Iris wine-red, dark brown in young birds, eye-ring greenish-grey. Tarsus greenish-horn. Upper mandible black, sometimes marked with yellow and paler at tip, lower mandible yellow at base, darker at tip.

 

Similar species: This species very closely resembles the Streak-breasted Woodpecker Picus viridanus which is not found in Singapore but does occur in peninsular Malaysia.

 

Picus vittatus: Chin, throat and upper breast dull brownish-olive, with no streaks. Lower breast dark brownish-buff with fine lacy marks.

 

Picus viridanus: Throat greener, lightly streaked. Entire breast green, with bold scaly streaks.

 

Status, Habitat & Behaviour: A coastal species found in the casuarinas and mangrove belt from Perak down to Johore and Singapore, it is common on both sides of the Johore Straits but is rarely found inland (Robinson & Chasen 1939). While Burknill & Chasen (1927) considered it unlikely to be found in gardens or near town, the degree of forest clearance since then may have changed things somewhat.

 

Medway & Wells (1976) found it in mangrove and adjacent secondary growth to, at the most, 24 km inland in coconut plantations and village gardens. Wells (1999) found it common near the coast, less so inland, but noted its landward expansion, particularly since 1970's, into oil palm and rubber plantations, nearby wooded gardens and parkland up to 30 km from the sea, but strictly at plains level.

 

Since the early 1900's, there has been much debate, and confusion, over its taxonomy, as well as its status and relationships to very similar birds, such as the Streak-breasted Woodpecker Picus viridanus and the Streak-throated Woodpecker Picus xanthopygaeus, found in peninsular Malaya, Thailand and Myanmar. This debate still continues, and further taxonomic migration can be anticipated. As a result, very little of the early data, on its habits and behaviour, can safely be ascribed to this species.

 

Found singly, in pairs or in small family parties, it is not a shy bird. Most often, it is seen on tree trunks, its tail depressed and partly fanned out to support it against the bark, climbing upwards, often going round and round the trunk in short jerky movements, sometimes hopping backwards for a pace or two. Every now and again, it stops and, with its head cocked to one side, peers very intently at the tree bark, possibly to listen for activity beneath the bark, occasionally tapping tentatively at the bark with its bill. Whenever it suspects the presence of its prey, it starts pecking furiously away, vigorously enough to send wood chips flying all around it, then inserts its tongue into the cavity to extract food.

 

The bird frequently finds its food on the fallen trunks of trees, in tall grass, and can regularly be seen feeding on the ground, the tail pressed against the ground, the body held upright. The underparts of several museum specimens were sullied with mud, suggesting that the birds had fed on the ground or on the roots of mangrove (Burknill & Chasen 1927). In Perak, they were seen searching for food among the fallen leaves in a rubber estate (Edgar 1933). A pair was seen feeding on the ground in Singapore too (Kwong 2011).

 

Occasionally, it can be seen perched on tree trunks or stumps, sunning itself with one or both wings partly outstretched. When disturbed, it flies a short distance to land on the lower branches of a nearby tree. Its flight is strong and undulating.

 

Food: Like all woodpeckers, it feeds mainly on termites, ants and other small insects, including the larvae and eggs of wood-boring insects, hidden in decaying wood or within the hollow stems of various plants. It finds its prey by chiselling into the rotting wood. Then, using its long and greatly extensible tongue, the barbed tip covered with glutinous saliva, it probes deep into the cavity to extract the prey. In Singapore, a bird was seen on the ground, apparently eating worms (Jane 2010).

 

There is very little by way of detailed information specific to its diet but it has been known to eat fruit and berries. A congeneric species, the Streak-throated Woodpecker Picus xanthopygaeus, takes the nectar of flowers from the Erythrina and Salmalia trees, and drinks juice from date palms tapped for toddy (Ali & Ripley 1970). From Singapore, there are reports of this bird feeding at a durian tree Durio zibethinus (Goh et al 2006), and on an oil palm tree Elaeis guineensis (Chow 2011) - whether the bird was actually eating the fruit, drinking the sap or feeding on insects remains unclear. Additionally, there is an early record, from 1989, of this bird being seen "pecking and gobbling the juicy flesh of rambutans" but the actual source of this citation, however, remains elusive.

 

Voice and Calls: Its call is a high-pitched and fairly loud kek, repeated about a dozen times, every two to three seconds or so.

 

Breeding: In Singapore, nest building has been recorded from December to April and June, brooding in April and May, chicks in June, and young birds were seen in June and August (Wang & Hails 2007). In Perak, West Malaysia, nests were found from March to April (Edgar 1933). Medway & Wells (1976) have recorded nests between February and June.

 

Like all woodpeckers, it nests in holes excavated into tree trunks. Their nests, situated 1 to 9 m (3 to 30 feet) above the ground level, have been found on an "api-api' tree (Avicennia spp.), dead coconut trees Cocos nucifera, on a hog-plum tree Spondias spp, a dead mango tree Mangifera spp (Edgar 1933) and on a casuarina tree (Madoc 1956). Though it appears to nest mainly on dead trunks, some nests have been excavated into living trees (Wells 1999).

 

The normal clutch consists of four eggs, pinkish-white, fairly glossy, the average size varying from 26.4 x 19.1 mm. to 27.4 x 21.1 mm. (Edgar 1933). Both sexes help excavate the nest, incubate the eggs and feed the young. Very little is known of its courtship behaviour or its breeding biology.

 

Moult: In Genus Picidae, the primaries moult descendantly and sequentially, the secondaries from two centres, ascendantly from S1 (starting after P5), ascendantly and descendantly from S8 (starting with P3). Tail moult is centrifugal. Post-nuptial is complete. Post-juvenile moult is partial, of primaries, tail and body but not the secondaries, primary coverts or tertials though, sometimes, one or two tertials may be replaced. Occasionally, the outer primary coverts are also moulted, with contrast between the new and old feathers showing (Baker 1993).

 

On 26th August, a family party of two adults and an immature bird was caught at Ulu Pandan in Singapore. The male, with an ill-defined brood patch, was in post-nuptial moult. Wing: P1 to P4 = 5, P5 = 3, P6 = 1, rest = 0, S1 = 4, S2 to S5 = 0, S6 to S8 = 5. Tail: T1 = 0, T2 = 2, T3 = 1, rest = 0. The female, with a distinct brood patch, was also in post-nuptial moult. Wing: P1 to P3 = 5, P4 = 4, P5 = 2, rest = 0. S1 to S6 = 0, S7 to S8 = 5. Tail: T1 = 0, T2 = 1, rest = 0. The immature bird, a female, was undergoing post-juvenile moult. Wing: P1 to P2 = 5, P3 = 4, P4 = missing, rest = 0 (Wang 1999).

 

Miscellaneous: Generally speaking, birds are said to have very little sense of smell or taste. Whether woodpeckers have an acute sense of hearing which enables them to detect the movements of prey items hidden within the wood or whether tapping at the wood with the bill enables them to locate any prey in hidden hollows beneath the surface of the wood, is not entirely clear.

 

The bone structure in a woodpecker's skull is part of an evolutionary adaptation that enables it to hammer away into tree trunks without suffering damage to its brain. Its tongue, too, often more than twice the length of the bird's skull, is just as specialised. More information about this can be obtained from the ON Nature magazine, or the Wild Birds Unlimited site.

 

To discover how the development of the woodpecker's skull has helped inspire the development of shock absorbers, please visit this page published in the New Scientist. The original paper it cites, a highly technical and detailed effort, A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems (Yoon & Park 2011), can be obtained at the IOPscience website.

 

Two adult birds ringed at Rantau Panjang were recaptured there 116 and 120 months later (Medway & Wells 1976).

  

[Credit: singaporebirds.net/]

Note: This post was originally published at Napsterization.org/stories.

 

This is a diagram showing the non-profit organizations (note: no for-profits, conferences or governmental orgs were included) that are stewarding pieces of the Personal Data Ecosystem. I wanted to show how the orgs are relating to the problem of how to remake our digital lives, through more user-driven personal data, for more equal transactions throughout our lives with companies, the online world, and our government.

 

The orgs have been divided into four areas: technical, market, policy and individual advocates. While all the orgs have an interest and are doing some thinking in all the areas, these divisions show the foundational mission of the orgs. If each org, through its foundation mission, succeeded, they would be heros for sure. The problem is, mission creep. This is a problem for startups as well, where companies don't focus and get their piece right to succeed, but rather think competitively and try to take too many pieces of the market, leading to failure. So too will the large number of problems, plus mission creep, cause any of these orgs to fail at their mission.

 

Ideally, we'll see all the orgs working together in inter-disciplinary and multi-disciplinary ways, relating each of their solutions to the others, but keeping focused and executing their piece of this vast and Byzantine puzzle to solve the Personal Data Ecosystem. In creating this "org chart" I talked with folks like Kevin Marks of Microformats and Activity Streams, Harry Halpin of the Federated Social Web, Scott David, Don Thibeau of OIX and OpenID, Drummond Reed (who has worked with OASIS extensively), Doc Searls of VRM, Craig Burton, Steve Rappetti and Phil Wolff of Data Portability project, Dazza Greenwood of ID Cubed, Judi Clark and Joe Andrieu of Information Sharing Working Group, among others.

 

So here is a picture of who is doing what in the Personal Data space:

   

Below is more information on these organizations.

 

Individual Solutions

 

Customer Commons -- recently formed by Doc and Joyce Searls, Renee Lloyd, Joe Andrieu, Dean Landsman, Markus Sabadello, Judi Clark, Iain Henderson, Craig Burton, and me, as well as a few others in the room that, I apologize, I'm forgetting. Customer Commons' mission is: a community of customers, funded only by customers, serving the interests and aspirations of customers.

 

Market Solutions

 

Personal Data Ecosystem Consortium -- is a trade association for startups and big companies that agree to a set of principles for user-driven personal data. 19 companies (currently) have joined, and PDEC's mission is to support market solutions to the personal data question. Kaliya Hamlin is Executive Director and I am Chair of the Board.

 

PDEC also has just formed a Legal Town Hall, a monthly call starting January 11, 2012, to be led by Judi Clark, to talk about what kind of policies are needed when individuals share their data.

 

World Economic Forum -- WEF has been working with lots of early thinkers in the Personal Data space for the past 18 months to "rethink personal data." They put out a report: Personal Data: a New Asset Class last February and continue to have monthly calls to prepare for a presentation of the working groups' efforts at Davos in January.

 

Project VRM -- Vendor Relationships Management, the brainchild of Doc Searls created during his fellowship at the Berkman Center, is a discussion group with a very active maillist, a movement for user-driven relationships with entities, and a steward of developers coding to bear out the group's vision.

 

Policy Solutions

 

OIX: Open Identity Exchange -- Don Thibeau is Chair of their Board, and Scott David is their counsel. OIX's mission is to build trust in the exchange of identity credentials online. They do this through the open, standardization of Trust Frameworks. They don't make trust frameworks, but rather their mission is to be the home of other's trust frameworks for the sharing of personal data, login credentials, and other types of private or controlled information. For example, the company Drummond Reed co-founded, Connect.me, Connect.Me, hosts the Respect Trust Framework at OIX, who publishes it for others to point to as a public declaration of the trust framework. And, the U.S. FICAM Trust Framework was the first open identity trust framework to be listed by OIX

 

Information Sharing Working Group -- From the ISWG: The ISWG works with the Kantara Initiative, Identity Commons, Project VRM, the Personal Data Ecosystem Consortium, and Customer Commons. Run by co-chairs, Joe Andrieu and Iain Henderson and secretary Judi Clark, ISWG's formal mission is "to identify and document the use cases and scenarios that illustrate the various sub-sets of user driven information, the benefits therein, and specify the policy and technology enablers that should be put in place to enable this information to flow."

 

The Information Sharing Work Group helps individuals take control of the information we share online. The Standard Information Sharing Agreement is a contract for the use of your information, agreed to BEFORE you share it. It has two parts. A basic agreement covers all the default terms, things like “don’t redistribute my information without my permission”, which all recipients agree to. Then, for each individual instance of sharing, a data transaction agreement with just the bare essentials: who gets what data for what purpose. By moving all the complicated legalese into the basic agreement, we’ve dramatically simplified each specific transaction agreement.

 

Now, when you want to know what’s happening with your data, it’s presented simply and concisely in easy-to-understand terms… while the basic agreement defines how recipients must treat your data appropriately. The Sharing Agreement is designed to make it easy to understand and make informed decisions about sharing information online.

 

ID Cubed (ID3) -- a newly formed research and developement group affiliated with MIT and led by John Clippinger, Executive Director and CEO, (who started the Law Lab at Berkman/Harvard a couple of years ago and the Social Physics project a couple of years before that, also at Berkman) and Henrik Sandell, COO and CTO of ID3. ID3's mission is to "oversee the development of a multi-disciplinary center founded to research the role of law in facilitating cooperation and entrepreneurial innovation." Their major focus based upon the website seems to be Trust Framework development. Dazza Greenwood is also involved, as is Mike Schwartz of Gluu is doing some technical work for them.

 

Technical Solutions

 

Data Portability Project -- "Aims to consult, design, educate and advocate interoperable data portability to users, developers and vendors." They don't make standards but they help steward them to support more data portability, including protocols like OpenID, OAuth, RSS, Microformats and RDF among others. Steve Repetti is their Chair and Phil Wolff is very active as a public speaker for them. Here is some additional information about their mission.

 

Federated Social Web -- has recently become a working group of W3C, and is stewarded by many including Evan Prodromou and Harry Halpin. FSW is stewarding work on federated social web software and protocols, including things like PubSubHubBub, OpenID, Activity Streams, OAuth, among many protocols.

 

Activity Streams -- developed a protocol for how user's share personal data, using both JSON and Atom based streams of metadata. Monica Wilkinson and Kevin Marks actively steward the project. Activity Streams works on the Microformats model, proposing standards around activities already heaving in used online.

 

Microformats -- Microformats have been created for many pieces of data shared, such as hcard or hcalendar. Stewards of this project include Tantek Celik and Kevin Marks.

 

OpenID -- Created protocol for a federated login with OpenID 2.0 spec. OpenID Foundation is currently working with Microsoft, Google and Facebook on OpenID Connect, as well as on Account Chooser, an open standard for web sign-in ease switching between multiple accounts on a website. OpenID Foundation's chair is Don Thibeau.

 

ID Trust, OASIS -- from their website: "...promotes greater understanding and adoption of standards-based identity and trusted infrastructure technologies, policies, and practices. The group provides a neutral setting where government agencies, companies, research institutes, and individuals work together to advance the use of trusted infrastructures, including the Public Key Infrastructure (PKI)."

 

XDI.org -- responsible for the XRI / XDI standard, currently for pointing to data and creating link contracts. From their website: "XDI.ORG is an international non-profit public trust organization governing open public XRI and XDI infrastructure. XRI (Extensible Resource Identifier) and XDI (XRI Data Interchange) are open standards for digital identity addressing and trusted data sharing developed at OASIS, the leading XML e-business standards body. XRI and XDI infrastructure enables individuals and organizations to establish persistent, privacy-protected Internet identities and form long-term, trusted peer-to-peer data sharing relationships." Drummond Reed co-chaired the group with well, Gabe Wachob, of the XRI TC at OASIS and Andy Dale, Markus Sabadello, Mike Schwartz we involved in developing the standard.

 

W3C -- Umbrella standards body stewarding a number of standards for personal data use and control including the Do Not Track proposal. The Federated Social Web, and all their combined efforts including Activity Streams, recently landed at W3C.

 

ITU (International Telecommunications Unit) -- making infocommunications standards since 1865. Yes.. that's really 1865.

 

User Managed Access (UMA), a Kantara working group -- develops specs to allow individuals to "control the authorization of data sharing and service access made between online services on the individual's behalf, and to facilitate interoperable implementations of the specs." UMA group chair is Eve Maler.

 

The Direct Project -- From their website: "The Direct Project specifies a simple, secure, scalable, standards-based way for participants to send authenticated, encrypted health information directly to known, trusted recipients over the Internet."

 

IETF (Internet Engineering Task Force) -- Working on a number of standards around identity and data portability.

 

Claims Agent Working Group -- is working on development of standards-based, interoperable, verified claims agent implementations. Is at IDCommons and was originally proposed by Paul Trevithick, though many people are part of the group.

 

Open Web Foundation -- is "independent non-profit dedicated to the development and protection of open, non-proprietary specifications for web technologies" and uses an open source model similar to the Apache Foundation. Their leadership includes Tantek Celik, Chris Messina & David Recordon.

 

Update: I've added the following item to technical:

 

SWIFT -- a non-profit based in Brussels that provides messaging standards around banking wires, is proposing a new infrastructure layer called the "Digital Asset Grid." The DAG would provide the metadata for all data transactions (including personal data), not just money wires, as well as a hardened, full duplex transaction layer for security, flexible identity and certified data. (Full disclosure, I'm on the team that proposed the Digital Asset Grid to SWIFT).

 

If you have more information about these groups, people involved, or corrections, please leave them in the comments and I'll update the post. Thanks!

A small slow-moving lizard with a long extensible tongue and tail.It has protruding eyes that rotate independently, and has the ability to change body colour hence the name 'Chameleon' I always thought a chameleon changed colour to hide but have just recently found out it's in fact the way that they communicate with each other.

Prototype of the Mercury, an infinitely extensible, open camera system that I developed over the past two years, with some help from others. This one is shown configured for 4x5 large format.

O beija-flor é uma ave da família Trochilidae, composta por 108 gêneros e 322 espécies conhecidas. Entre as características distintivas do grupo contam-se o bico alongado, a alimentação à base de néctar, oito pares de costelas, catorze a quinze vértebras cervicais, plumagem iridescente e uma língua extensível e bifurcada. O grupo é originário das Américas e ocorre desde o Alasca à Terra do Fogo. A maioria das espécies é tropical e subtropical, vivendo entre as latitudes 10ºN e 25ºS. A maior biodiversidade do grupo encontra-se no Brasil e no Equador, que contam com cerca de metade das espécies conhecidas de beija-flor. Os beija-flores são aves de pequeno porte, que medem em média de seis a doze centímetros de comprimento e pesam de dois a seis gramas. O bico é normalmente longo, mas o formato preciso varia bastante com a espécie e está adaptado ao formato da flor que constitui a base da alimentação de cada tipo de beija-flor. Uma característica comum é a língua bifurcada e extensível, usada para extrair o néctar das flores.

 

The hummingbird is a bird of the family Trochilidae, composed of 108 genera and 322 known species. Among the distinguishing characteristics of the group are elongated beak, nectar-based feeding, eight pairs of ribs, fourteen to fifteen cervical vertebrae, iridescent plumage and an extensible and forked tongue. The group originates in the Americas and occurs from Alaska to Tierra del Fuego. Most species are tropical and subtropical, living between latitudes 10ºN and 25ºS. The group's greatest biodiversity is in Brazil and Ecuador, which account for about half of the known species of hummingbird. Hummingbirds are small birds, measuring an average of six to twelve centimeters in length and weighing two to six grams. The beak is usually long, but the precise shape varies greatly with the species and is adapted to the shape of the flower that forms the basis of the feeding of each type of hummingbird. A common feature is the forked and extensible tongue used to extract nectar from flowers.

 

Adaptado de @Wikipedia pt.wikipedia.org/wiki/Beija-flor

 

Adapted from @Wikipedia

An even better view of the engine icicles. This one shows the Common Extensible Cryogenic Engine (CECE) at about 10% power, and the ice is just dripping from the rim of the nozzle.

 

The one from 1/14/09 shows the CECE at 100% power, and the ice is less dramatic. That's this one: www.flickr.com/photos/28634332@N05/3196622357/

 

Pretty cool. And if you wonder why this matters -- beyond making a great photo -- it's because this is part of the testing that may help astronauts land on the moon:

 

www.nasa.gov/mission_pages/constellation/news/cece.html

 

A wild tangent inspired by Dominik Strzelec's Processing demo of catenary curves in Toxiclibs.

 

I was curious about the simulation aspect and how it might relate to parametric modeling, but then I added some basic color shading and promptly forgot about everything else. Sketches like these don't really have a defined place in my current practice and I usually only get to show them in lectures, so by now I have a growing elephant graveyard of code sketches like these.

 

I'm embarrassed to say this is the first time I've seriously used Toxiclibs for more than 20 minutes. It really is a thing of beauty and contains some very powerful tools once you figure out Karsten's code structure. Most coders tend towards idiosyncracy and Karsten is no exception, but his manifests itself in the form of well-thought out and extensible code structures while mine are far less elegant.

 

I plan to post a version of my sketch on OpenProcessing as a nod to Dominik for using his code. The physical simulation is still Toxiclibs, but I've moved all rendering, GUI and meshing to Modelbuilder for my own convenience's sake.

Prototype of the Mercury, an infinitely extensible, open camera system that I developed over the past two years, with some help from others. This one is shown configured to shoot Instax Mini.

A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος anisos, "unequal" and πτερόν pteron, "wing", because the hindwing is broader than the forewing). Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Dragonflies can be mistaken for the related group, damselflies (Zygoptera), which are similar in structure, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold their wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight. Many dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each.

 

Fossils of very large dragonfly-like insects, sometimes called griffinflies, are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in), but were only distant ancestors, not true dragonflies. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world.

 

Dragonflies are predators, both in their aquatic nymphs stage (also known as naiads) and as adults. In some species, the nymphal stage lasts for up to five years, and the adult stage may be as long as ten weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. They are fast, agile fliers, sometimes migrating across oceans, and often live near water. They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, and sperm competition. During mating, the male grasps the female at the back of the head, and the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture.

 

Dragonflies are represented in human culture on artefacts such as pottery, rock paintings, statues and Art Nouveau jewellery. They are used in traditional medicine in Japan and China, and caught for food in Indonesia. They are symbols of courage, strength, and happiness in Japan, but seen as sinister in European folklore. Their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates.

   

Evolution

 

Dragonflies and their relatives are similar in structure to an ancient group, meganisoptera, from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that ever lived, Meganeuropsis permiana from the Early Permian, with a wingspan around 750 mm (30 in);. Known informally as "griffinflies", their fossil record ends with the Permian–Triassic extinction event (about 247 Mya). The Protanisoptera, another ancestral group that lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, and are known from fossil wings from current-day United States, Russia, and Australia, suggesting they might have been cosmopolitan in distribution. While both of those groups are sometimes referred to as "giant dragonflies", in fact true dragonflies/odonata are more modern insects that had not evolved yet.

 

Modern dragonflies do retain some traits of their distant predecessors, and are in a group known as palaeoptera, ancient-winged. They, like the gigantic pre-dinosaur griffinflies, lack the ability to fold their wings up against their bodies in the way modern insects do, although some evolved their own different way to do so. The forerunners of modern Odonata are included in a clade called the Panodonata, which include the basal Zygoptera (damselflies) and the Anisoptera (true dragonflies). Today, some 3,000 species are extant around the world.

 

The relationships of anisopteran families are not fully resolved as of 2013, but all the families are monophyletic except the Corduliidae; the Gomphidae are a sister taxon to all other Anisoptera, the Austropetaliidae are sister to the Aeshnoidea, and the Chlorogomphidae are sister to a clade that includes the Synthemistidae and Libellulidae. On the cladogram, dashed lines indicate unresolved relationships; English names are given (in parentheses)

   

Distribution and diversity

 

About 3,012 species of dragonflies were known in 2010; these are classified into 348 genera in 11 families. The distribution of diversity within the biogeographical regions are summarized below (the world numbers are not ordinary totals, as overlaps in species occur).

 

Dragonflies live on every continent except Antarctica. In contrast to the damselflies (Zygoptera), which tend to have restricted distributions, some genera and species are spread across continents. For example, the blue-eyed darner Rhionaeschna multicolor lives all across North America, and in Central America; emperors Anax live throughout the Americas from as far north as Newfoundland to as far south as Bahia Blanca in Argentina, across Europe to central Asia, North Africa, and the Middle East. The globe skimmer Pantala flavescens is probably the most widespread dragonfly species in the world; it is cosmopolitan, occurring on all continents in the warmer regions. Most Anisoptera species are tropical, with far fewer species in temperate regions.

 

Some dragonflies, including libellulids and aeshnids, live in desert pools, for example in the Mojave Desert, where they are active in shade temperatures between 18 and 45 °C (64.4 to 113 °F); these insects were able to survive body temperatures above the thermal death point of insects of the same species in cooler places.

 

Dragonflies live from sea level up to the mountains, decreasing in species diversity with altitude. Their altitudinal limit is about 3700 m, represented by a species of Aeshna in the Pamirs.

 

Dragonflies become scarce at higher latitudes. They are not native to Iceland, but individuals are occasionally swept in by strong winds, including a Hemianax ephippiger native to North Africa, and an unidentified darter species. In Kamchatka, only a few species of dragonfly including the treeline emerald Somatochlora arctica and some aeshnids such as Aeshna subarctica are found, possibly because of the low temperature of the lakes there. The treeline emerald also lives in northern Alaska, within the Arctic Circle, making it the most northerly of all dragonflies.

   

General description

 

Dragonflies (suborder Anisoptera) are heavy-bodied, strong-flying insects that hold their wings horizontally both in flight and at rest. By contrast, damselflies (suborder Zygoptera) have slender bodies and fly more weakly; most species fold their wings over the abdomen when stationary, and the eyes are well separated on the sides of the head.

 

An adult dragonfly has three distinct segments, the head, thorax, and abdomen, as in all insects. It has a chitinous exoskeleton of hard plates held together with flexible membranes. The head is large with very short antennae. It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of ommatidia, the numbers being greater in the larger species. Aeshna interrupta has 22650 ommatidia of two varying sizes, 4500 being large. The facets facing downward tend to be smaller. Petalura gigantea has 23890 ommatidia of just one size. These facets provide complete vision in the frontal hemisphere of the dragonfly. The compound eyes meet at the top of the head (except in the Petaluridae and Gomphidae, as also in the genus Epiophlebia). Also, they have three simple eyes or ocelli. The mouthparts are adapted for biting with a toothed jaw; the flap-like labrum, at the front of the mouth, can be shot rapidly forward to catch prey. The head has a system for locking it in place that consists of muscles and small hairs on the back of the head that grip structures on the front of the first thoracic segment. This arrester system is unique to the Odonata, and is activated when feeding and during tandem flight.

 

The thorax consists of three segments as in all insects. The prothorax is small and is flattened dorsally into a shield-like disc, which has two transverse ridges. The mesothorax and metathorax are fused into a rigid, box-like structure with internal bracing, and provide a robust attachment for the powerful wing muscles inside. The thorax bears two pairs of wings and three pairs of legs. The wings are long, veined, and membranous, narrower at the tip and wider at the base. The hindwings are broader than the forewings and the venation is different at the base. The veins carry haemolymph, which is analogous to blood in vertebrates, and carries out many similar functions, but which also serves a hydraulic function to expand the body between nymphal stages (instars) and to expand and stiffen the wings after the adult emerges from the final nymphal stage. The leading edge of each wing has a node where other veins join the marginal vein, and the wing is able to flex at this point. In most large species of dragonflies, the wings of females are shorter and broader than those of males. The legs are rarely used for walking, but are used to catch and hold prey, for perching, and for climbing on plants. Each has two short basal joints, two long joints, and a three-jointed foot, armed with a pair of claws. The long leg joints bear rows of spines, and in males, one row of spines on each front leg is modified to form an "eyebrush", for cleaning the surface of the compound eye.

 

The abdomen is long and slender and consists of 10 segments. Three terminal appendages are on segment 10; a pair of superiors (claspers) and an inferior. The second and third segments are enlarged, and in males, on the underside of the second segment has a cleft, forming the secondary genitalia consisting of the lamina, hamule, genital lobe, and penis. There are remarkable variations in the presence and the form of the penis and the related structures, the flagellum, cornua, and genital lobes. Sperm is produced at the 9th segment, and is transferred to the secondary genitalia prior to mating. The male holds the female behind the head using a pair of claspers on the terminal segment. In females, the genital opening is on the underside of the eighth segment, and is covered by a simple flap (vulvar lamina) or an ovipositor, depending on species and the method of egg-laying. Dragonflies having simple flaps shed the eggs in water, mostly in flight. Dragonflies having ovipositors use them to puncture soft tissues of plants and place the eggs singly in each puncture they make.

 

Dragonfly nymphs vary in form with species, and are loosely classed into claspers, sprawlers, hiders, and burrowers. The first instar is known as a prolarva, a relatively inactive stage from which it quickly moults into the more active nymphal form. The general body plan is similar to that of an adult, but the nymph lacks wings and reproductive organs. The lower jaw has a huge, extensible labium, armed with hooks and spines, which is used for catching prey. This labium is folded under the body at rest and struck out at great speed by hydraulic pressure created by the abdominal muscles. Whereas damselfly nymphs have three feathery external gills, dragonfly nymphs have internal gills, located around the fourth and fifth abdominal segments. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails (Gomphidae) that burrow into the sediment, have a snorkel-like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.

   

Colouration

 

Many adult dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. Their overall colouration is often a combination of yellow, red, brown, and black pigments, with structural colours. Blues are typically created by microstructures in the cuticle that reflect blue light. Greens often combine a structural blue with a yellow pigment. Freshly emerged adults, known as tenerals, are often pale-coloured and obtain their typical colours after a few days, some have their bodies covered with a pale blue, waxy powderiness called pruinosity; it wears off when scraped during mating, leaving darker areas.

 

Some dragonflies, such as the green darner, Anax junius, have a noniridescent blue that is produced structurally by scatter from arrays of tiny spheres in the endoplasmic reticulum of epidermal cells underneath the cuticle.

 

The wings of dragonflies are generally clear, apart from the dark veins and pterostigmata. In the chasers (Libellulidae), however, many genera have areas of colour on the wings: for example, groundlings (Brachythemis) have brown bands on all four wings, while some scarlets (Crocothemis) and dropwings (Trithemis) have bright orange patches at the wing bases. Some aeshnids such as the brown hawker (Aeshna grandis) have translucent, pale yellow wings.

 

Dragonfly nymphs are usually a well-camouflaged blend of dull brown, green, and grey.

   

Biology

 

Ecology

 

Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on tadpoles and small fish. Adults capture insect prey in the air, making use of their acute vision and highly controlled flight. The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilization, and sperm competition.

 

Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.

 

Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements. Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water. Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as Sympetrum (darters) have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there. Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in Aeshna viridis (green hawker), which lives in swamps with the water-soldier, Stratiotes aloides. The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and pH can also affect its use by dragonflies. Most species need moderate conditions, not too eutrophic, not too acidic; a few species such as Sympetrum danae (black darter) and Libellula quadrimaculata (four-spotted chaser) prefer acidic waters such as peat bogs, while others such as Libellula fulva (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.

   

Behaviour

 

Many dragonflies, particularly males, are territorial. Some defend a territory against others of their own species, some against other species of dragonfly and a few against insects in unrelated groups. A particular perch may give a dragonfly a good view over an insect-rich feeding ground; males of many species such as the Pachydiplax longipennis (blue dasher) jostle other dragonflies to maintain the right to alight there. Defending a breeding territory is common among male dragonflies, especially in species that congregate around ponds. The territory contains desirable features such as a sunlit stretch of shallow water, a special plant species, or the preferred substrate for egg-laying. The territory may be small or large, depending on its quality, the time of day, and the number of competitors, and may be held for a few minutes or several hours. Dragonflies including Tramea lacerata (black saddlebags) may notice landmarks that assist in defining the boundaries of the territory. Landmarks may reduce the costs of territory establishment, or might serve as a spatial reference. Some dragonflies signal ownership with striking colours on the face, abdomen, legs, or wings. The Plathemis lydia (common whitetail) dashes towards an intruder holding its white abdomen aloft like a flag. Other dragonflies engage in aerial dogfights or high-speed chases. A female must mate with the territory holder before laying her eggs. There is also conflict between the males and females. Females may sometimes be harassed by males to the extent that it affects their normal activities including foraging and in some dimorphic species females have evolved multiple forms with some forms appearing deceptively like males. In some species females have evolved behavioural responses such as feigning death to escape the attention of males. Similarly, selection of habitat by adult dragonflies is not random, and terrestrial habitat patches may be held for up to 3 months. A species tightly linked to its birth site utilises a foraging area that is several orders of magnitude larger than the birth site.

   

Reproduction

 

Mating in dragonflies is a complex, precisely choreographed process. First, the male has to attract a female to his territory, continually driving off rival males. When he is ready to mate, he transfers a packet of sperm from his primary genital opening on segment 9, near the end of his abdomen, to his secondary genitalia on segments 2–3, near the base of his abdomen. The male then grasps the female by the head with the claspers at the end of his abdomen; the structure of the claspers varies between species, and may help to prevent interspecific mating. The pair flies in tandem with the male in front, typically perching on a twig or plant stem. The female then curls her abdomen downwards and forwards under her body to pick up the sperm from the male's secondary genitalia, while the male uses his "tail" claspers to grip the female behind the head: this distinctive posture is called the "heart" or "wheel"; the pair may also be described as being "in cop".

 

Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but also the male hovering above her or continuing to clasp her and flying in tandem. The male attempts to prevent rivals from removing his sperm and inserting their own, something made possible by delayed fertilisation and driven by sexual selection. If successful, a rival male uses his penis to compress or scrape out the sperm inserted previously; this activity takes up much of the time that a copulating pair remains in the heart posture. Flying in tandem has the advantage that less effort is needed by the female for flight and more can be expended on egg-laying, and when the female submerges to deposit eggs, the male may help to pull her out of the water.

 

Egg-laying takes two different forms depending on the species. The female in some families has a sharp-edged ovipositor with which she slits open a stem or leaf of a plant on or near the water, so she can push her eggs inside. In other families such as clubtails (Gomphidae), cruisers (Macromiidae), emeralds (Corduliidae), and skimmers (Libellulidae), the female lays eggs by tapping the surface of the water repeatedly with her abdomen, by shaking the eggs out of her abdomen as she flies along, or by placing the eggs on vegetation. In a few species, the eggs are laid on emergent plants above the water, and development is delayed until these have withered and become immersed.

   

Life cycle

 

Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges. Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic nymphs or naiads which moult between six and 15 times (depending on species) as they grow. Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as mosquito larvae, tadpoles, and small fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some naiads, such as the later stages of Antipodophlebia asthenes, hunt on land.

 

The nymph stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. It remains stationary with its head out of the water, while its respiration system adapts to breathing air, then climbs up a reed or other emergent plant, and moults (ecdysis). Anchoring itself firmly in a vertical position with its claws, its skin begins to split at a weak spot behind the head. The adult dragonfly crawls out of its nymph skin, the exuvia, arching backwards when all but the tip of its abdomen is free, to allow its exoskeleton to harden. Curling back upwards, it completes its emergence, swallowing air, which plumps out its body, and pumping haemolymph into its wings, which causes them to expand to their full extent.

 

Dragonflies in temperate areas can be categorized into two groups, an early group and a later one. In any one area, individuals of a particular "spring species" emerge within a few days of each other. The springtime darner (Basiaeschna janata), for example, is suddenly very common in the spring, but disappears a few weeks later and is not seen again until the following year. By contrast, a "summer species" emerges over a period of weeks or months, later in the year. They may be seen on the wing for several months, but this may represent a whole series of individuals, with new adults hatching out as earlier ones complete their lifespans.

   

Sex ratios

 

The sex ratio of male to female dragonflies varies both temporally and spatially. Adult dragonflies have a high male-biased ratio at breeding habitats. The male-bias ratio has contributed partially to the females using different habitats to avoid male harassment. As seen in Hine's emerald dragonfly (Somatochlora hineana), male populations use wetland habitats, while females use dry meadows and marginal breeding habitats, only migrating to the wetlands to lay their eggs or to find mating partners. Unwanted mating is energetically costly for females because it affects the amount of time that they are able to spend foraging.

   

Flight

 

Dragonflies are powerful and agile fliers, capable of migrating across the sea, moving in any direction, and changing direction suddenly. In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, backward, to left and to right. They have four different styles of flight: A number of flying modes are used that include counter-stroking, with forewings beating 180° out of phase with the hindwings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift; phased-stroking, with the hindwings beating 90° ahead of the forewings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking; synchronised-stroking, with forewings and hindwings beating together, is used when changing direction rapidly, as it maximises thrust; and gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.

 

The wings are powered directly, unlike most families of insects, with the flight muscles attached to the wing bases. Dragonflies have a high power/weight ratio, and have been documented accelerating at 4 G linearly and 9 G in sharp turns while pursuing prey.

 

Dragonflies generate lift in at least four ways at different times, including classical lift like an aircraft wing; supercritical lift with the wing above the critical angle, generating high lift and using very short strokes to avoid stalling; and creating and shedding vortices. Some families appear to use special mechanisms, as for example the Libellulidae which take off rapidly, their wings beginning pointed far forward and twisted almost vertically. Dragonfly wings behave highly dynamically during flight, flexing and twisting during each beat. Among the variables are wing curvature, length and speed of stroke, angle of attack, forward/back position of wing, and phase relative to the other wings.

   

Flight speed

 

Old and unreliable claims are made that dragonflies such as the southern giant darner can fly up to 97 km/h (60 mph). However, the greatest reliable flight speed records are for other types of insects. In general, large dragonflies like the hawkers have a maximum speed of 36–54 km/h (22–34 mph) with average cruising speed of about 16 km/h (9.9 mph). Dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.

   

Motion camouflage

 

n high-speed territorial battles between male Australian emperors (Hemianax papuensis), the fighting dragonflies adjust their flight paths to appear stationary to their rivals, minimizing the chance of being detected as they approach.[a] To achieve the effect, the attacking dragonfly flies towards his rival, choosing his path to remain on a line between the rival and the start of his attack path. The attacker thus looms larger as he closes on the rival, but does not otherwise appear to move. Researchers found that six of 15 encounters involved motion camouflage.

   

Temperature control

 

The flight muscles need to be kept at a suitable temperature for the dragonfly to be able to fly. Being cold-blooded, they can raise their temperature by basking in the sun. Early in the morning, they may choose to perch in a vertical position with the wings outstretched, while in the middle of the day, a horizontal stance may be chosen. Another method of warming up used by some larger dragonflies is wing-whirring, a rapid vibration of the wings that causes heat to be generated in the flight muscles. The green darner (Anax junius) is known for its long-distance migrations, and often resorts to wing-whirring before dawn to enable it to make an early start.

 

Becoming too hot is another hazard, and a sunny or shady position for perching can be selected according to the ambient temperature. Some species have dark patches on the wings which can provide shade for the body, and a few use the obelisk posture to avoid overheating. This behaviour involves doing a "handstand", perching with the body raised and the abdomen pointing towards the sun, thus minimising the amount of solar radiation received. On a hot day, dragonflies sometimes adjust their body temperature by skimming over a water surface and briefly touching it, often three times in quick succession. This may also help to avoid desiccation.

   

Feeding

 

Adult dragonflies hunt on the wing using their exceptionally acute eyesight and strong, agile flight. They are almost exclusively carnivorous, eating a wide variety of insects ranging from small midges and mosquitoes to butterflies, moths, damselflies, and smaller dragonflies. A large prey item is subdued by being bitten on the head and is carried by the legs to a perch. Here, the wings are discarded and the prey usually ingested head first. A dragonfly may consume as much as a fifth of its body weight in prey per day. Dragonflies are also some of the insect world's most efficient hunters, catching up to 95% of the prey they pursue.

 

The nymphs are voracious predators, eating most living things that are smaller than they are. Their staple diet is mostly bloodworms and other insect larvae, but they also feed on tadpoles and small fish. A few species, especially those that live in temporary waters, are likely to leave the water to feed. Nymphs of Cordulegaster bidentata sometimes hunt small arthropods on the ground at night, while some species in the Anax genus have even been observed leaping out of the water to attack and kill full-grown tree frogs.

   

Eyesight

 

Dragonfly vision is thought to be like slow motion for humans. Dragonflies see faster than we do; they see around 200 images per second. A dragonfly can see in 360 degrees, and nearly 80 percent of the insect's brain is dedicated to its sight.

   

Predators

 

Although dragonflies are swift and agile fliers, some predators are fast enough to catch them. These include falcons such as the American kestrel, the merlin, and the hobby; nighthawks, swifts, flycatchers and swallows also take some adults; some species of wasps, too, prey on dragonflies, using them to provision their nests, laying an egg on each captured insect. In the water, various species of ducks and herons eat dragonfly nymphs and they are also preyed on by newts, frogs, fish, and water spiders. Amur falcons, which migrate over the Indian Ocean at a period that coincides with the migration of the globe skimmer dragonfly, Pantala flavescens, may actually be feeding on them while on the wing.

   

Parasites

 

Dragonflies are affected by three major groups of parasites: water mites, gregarine protozoa, and trematode flatworms (flukes). Water mites, Hydracarina, can kill smaller dragonfly nymphs, and may also be seen on adults. Gregarines infect the gut and may cause blockage and secondary infection. Trematodes are parasites of vertebrates such as frogs, with complex life cycles often involving a period as a stage called a cercaria in a secondary host, a snail. Dragonfly nymphs may swallow cercariae, or these may tunnel through a nymph's body wall; they then enter the gut and form a cyst or metacercaria, which remains in the nymph for the whole of its development. If the nymph is eaten by a frog, the amphibian becomes infected by the adult or fluke stage of the trematode.

   

Dragonflies and humans

 

Conservation

 

Most odonatologists live in temperate areas and the dragonflies of North America and Europe have been the subject of much research. However, the majority of species live in tropical areas and have been little studied. With the destruction of rainforest habitats, many of these species are in danger of becoming extinct before they have even been named. The greatest cause of decline is forest clearance with the consequent drying up of streams and pools which become clogged with silt. The damming of rivers for hydroelectric schemes and the drainage of low-lying land has reduced suitable habitat, as has pollution and the introduction of alien species.

 

In 1997, the International Union for Conservation of Nature set up a status survey and conservation action plan for dragonflies. This proposes the establishment of protected areas around the world and the management of these areas to provide suitable habitat for dragonflies. Outside these areas, encouragement should be given to modify forestry, agricultural, and industrial practices to enhance conservation. At the same time, more research into dragonflies needs to be done, consideration should be given to pollution control and the public should be educated about the importance of biodiversity.

 

Habitat degradation has reduced dragonfly populations across the world, for example in Japan. Over 60% of Japan's wetlands were lost in the 20th century, so its dragonflies now depend largely on rice fields, ponds, and creeks. Dragonflies feed on pest insects in rice, acting as a natural pest control. Dragonflies are steadily declining in Africa, and represent a conservation priority.

 

The dragonfly's long lifespan and low population density makes it vulnerable to disturbance, such as from collisions with vehicles on roads built near wetlands. Species that fly low and slow may be most at risk.

 

Dragonflies are attracted to shiny surfaces that produce polarization which they can mistake for water, and they have been known to aggregate close to polished gravestones, solar panels, automobiles, and other such structures on which they attempt to lay eggs. These can have a local impact on dragonfly populations; methods of reducing the attractiveness of structures such as solar panels are under experimentation.

   

In culture

 

A blue-glazed faience dragonfly amulet was found by Flinders Petrie at Lahun, from the Late Middle Kingdom of ancient Egypt.

 

Many Native American tribes consider dragonflies to be medicine animals that had special powers. For example, the southwestern tribes, including the Pueblo, Hopi, and Zuni, associated dragonflies with transformation. They referred to dragonflies as "snake doctors" because they believed dragonflies followed snakes into the ground and healed them if they were injured. For the Navajo, dragonflies symbolize pure water. Often stylized in a double-barred cross design, dragonflies are a common motif in Zuni pottery, as well as Hopi rock art and Pueblo necklaces.: 20–26 

 

As a seasonal symbol in Japan, the dragonflies are associated with season of autumn. In Japan, they are symbols of rebirth, courage, strength, and happiness. They are also depicted frequently in Japanese art and literature, especially haiku poetry. Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.: 38 

 

In Chinese culture, dragonflies symbolize both change and instability. They are also symbols in the Chinese practices of Feng Shui, where placements of dragonfly statues and artwork in parts of a home or office are believed to bring new insights and positive changes.

 

In both China and Japan, dragonflies have been used in traditional medicine. In Indonesia, adult dragonflies are caught on poles made sticky with birdlime, then fried in oil as a delicacy.

 

Images of dragonflies are common in Art Nouveau, especially in jewellery designs. They have also been used as a decorative motif on fabrics and home furnishings. Douglas, a British motorcycle manufacturer based in Bristol, named its innovatively designed postwar 350-cc flat-twin model the Dragonfly.

 

Among the classical names of Japan are Akitsukuni (秋津国), Akitsushima (秋津島), Toyo-akitsushima (豊秋津島). Akitsu is an old word for dragonfly, so one interpretation of Akitsushima is "Dragonfly Island". This is attributed to a legend in which Japan's mythical founder, Emperor Jimmu, was bitten by a mosquito, which was then eaten by a dragonfly.

 

In Europe, dragonflies have often been seen as sinister. Some English vernacular names, such as "horse-stinger", "devil's darning needle", and "ear cutter", link them with evil or injury. Swedish folklore holds that the devil uses dragonflies to weigh people's souls.: 25–27  The Norwegian name for dragonflies is Øyenstikker ("eye-poker"), and in Portugal, they are sometimes called tira-olhos ("eyes-snatcher"). They are often associated with snakes, as in the Welsh name gwas-y-neidr, "adder's servant". The Southern United States terms "snake doctor" and "snake feeder" refer to a folk belief that dragonflies catch insects for snakes or follow snakes around and stitch them back together if they are injured. Interestingly, the Hungarian name for dragonfly is szitakötő ("sieve-knitter").

 

The watercolourist Moses Harris (1731–1785), known for his The Aurelian or natural history of English insects (1766), published in 1780, the first scientific descriptions of several Odonata including the banded demoiselle, Calopteryx splendens. He was the first English artist to make illustrations of dragonflies accurate enough to be identified to species (Aeshna grandis at top left of plate illustrated), though his rough drawing of a nymph (at lower left) with the mask extended appears to be plagiarised.[b]

 

More recently, dragonfly watching has become popular in America as some birdwatchers seek new groups to observe.

 

In heraldry, like other winged insects, the dragonfly is typically depicted tergiant (with its back facing the viewer), with its head to chief.

   

In poetry and literature

 

Lafcadio Hearn wrote in his 1901 book A Japanese Miscellany that Japanese poets had created dragonfly haiku "almost as numerous as are the dragonflies themselves in the early autumn." The poet Matsuo Bashō (1644–1694) wrote haiku such as "Crimson pepper pod / add two pairs of wings, and look / darting dragonfly", relating the autumn season to the dragonfly. Hori Bakusui (1718–1783) similarly wrote "Dyed he is with the / Colour of autumnal days, / O red dragonfly."

 

The poet Lord Tennyson, described a dragonfly splitting its old skin and emerging shining metallic blue like "sapphire mail" in his 1842 poem "The Two Voices", with the lines "An inner impulse rent the veil / Of his old husk: from head to tail / Came out clear plates of sapphire mail."

 

The novelist H. E. Bates described the rapid, agile flight of dragonflies in his 1937 nonfiction book Down the River:

 

I saw, once, an endless procession, just over an area of water-lilies, of small sapphire dragonflies, a continuous play of blue gauze over the snowy flowers above the sun-glassy water. It was all confined, in true dragonfly fashion, to one small space. It was a continuous turning and returning, an endless darting, poising, striking and hovering, so swift that it was often lost in sunlight.

 

In technology

 

A dragonfly has been genetically modified with light-sensitive "steering neurons" in its nerve cord to create a cyborg-like "DragonflEye". The neurons contain genes like those in the eye to make them sensitive to light. Miniature sensors, a computer chip and a solar panel were fitted in a "backpack" over the insect's thorax in front of its wings. Light is sent down flexible light-pipes named optrodes[c] from the backpack into the nerve cord to give steering commands to the insect. The result is a "micro-aerial vehicle that's smaller, lighter and stealthier than anything else that's manmade".

 

[Credit: en.wikipedia.org/]

A wild tangent inspired by Dominik Strzelec's Processing demo of catenary curves in Toxiclibs.

 

I was curious about the simulation aspect and how it might relate to parametric modeling, but then I added some basic color shading and promptly forgot about everything else. Sketches like these don't really have a defined place in my current practice and I usually only get to show them in lectures, so by now I have a growing elephant graveyard of code sketches like these.

 

I'm embarrassed to say this is the first time I've seriously used Toxiclibs for more than 20 minutes. It really is a thing of beauty and contains some very powerful tools once you figure out Karsten's code structure. Most coders tend towards idiosyncracy and Karsten is no exception, but his manifests itself in the form of well-thought out and extensible code structures while mine are far less elegant.

 

I plan to post a version of my sketch on OpenProcessing as a nod to Dominik for using his code. The physical simulation is still Toxiclibs, but I've moved all rendering, GUI and meshing to Modelbuilder for my own convenience's sake.

Bats are mammals of the order Chiroptera (/kaɪˈrɒptərə/; from the Greek χείρ - cheir, "hand" and πτερόν - pteron, "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, can only glide for short distances. Bats do not flap their entire forelimbs, as birds do, but instead flap their spread-out digits, which are very long and covered with a thin membrane or patagium.

 

Bats are the second largest order of mammals (after the rodents), representing about 20% of all classified mammal species worldwide, with about 1,240 bat species divided into two suborders: the less specialized and largely fruit-eating megabats, or flying foxes, and the highly specialized and echolocating microbats. About 70% of bat species are insectivores. Most of the rest are frugivores, or fruit eaters. A few species, such as the fish-eating bat, feed from animals other than insects, with the vampire bats being hematophagous, or feeding on blood.

 

Bats are present throughout most of the world, with the exception of extremely cold regions. They perform vital ecological roles of pollinating flowers and dispersing fruit seeds; many tropical plant species depend entirely on bats for the distribution of their seeds. Bats are economically important, as they consume insect pests, reducing the need for pesticides. The smallest bat is the Kitti's hog-nosed bat, measuring 29–34 mm in length, 15 cm across the wings and 2–2.6 g in mass. It is also arguably the smallest extant species of mammal, with the Etruscan shrew being the other contender. The largest species of bat are a few species of Pteropus (fruit bats or flying foxes) and the giant golden-crowned flying fox with a weight up to 1.6 kg and wingspan up to 1.7 m.

 

CLASSIFICATION AND EVOLUTION

Bats are mammals. In many languages, the word for "bat" is cognate with the word for "mouse": for example, chauve-souris ("bald-mouse") in French, murciélago ("blind mouse") in Spanish, saguzahar ("old mouse") in Basque, летучая мышь ("flying mouse") in Russian, slijepi miš ("blind mouse") in Bosnian, nahkhiir ("leather mouse") in Estonian, vlermuis (winged mouse) in Afrikaans, from the Dutch word vleermuis (from Middle Dutch "winged mouse"). An older English name for bats is flittermouse, which matches their name in other Germanic languages (for example German Fledermaus and Swedish fladdermus). Bats were formerly thought to have been most closely related to the flying lemurs, treeshrews, and primates, but recent molecular cladistics research indicates that they actually belong to Laurasiatheria, a diverse group also containing Carnivora and Artiodactyla.

 

The two traditionally recognized suborders of bats are:

 

- Megachiroptera (megabats)

- Microchiroptera (microbats/echolocating bats)

 

Not all megabats are larger than microbats. The major distinctions between the two suborders are:

 

- Microbats use echolocation; with the exception of the Rousettus genus, megabats do not.

- Microbats lack the claw at the second finger of the forelimb.

- The ears of microbats do not close to form a ring; the edges are separated from each other at the base of the ear.

- Microbats lack underfur; they are either naked or have guard hairs.

 

Megabats eat fruit, nectar, or pollen. Most microbats eat insects; others may feed on fruit, nectar, pollen, fish, frogs, small mammals, or the blood of animals. Megabats have well-developed visual cortices and show good visual acuity, while microbats rely on echolocation for navigation and finding prey.

 

The phylogenetic relationships of the different groups of bats have been the subject of much debate. The traditional subdivision between Megachiroptera and Microchiroptera reflects the view that these groups of bats have evolved independently of each other for a long time, from a common ancestor already capable of flight. This hypothesis recognized differences between microbats and megabats and acknowledged that flight has only evolved once in mammals. Most molecular biological evidence supports the view that bats form a single or monophyletic group.

 

Researchers have proposed alternative views of chiropteran phylogeny and classification, but more research is needed.

 

In the 1980s, a hypothesis based on morphological evidence was offered that stated the Megachiroptera evolved flight separately from the Microchiroptera. The so-called flying primates theory proposes that, when adaptations to flight are removed, the Megachiroptera are allied to primates by anatomical features not shared with Microchiroptera. One example is that the brains of megabats show a number of advanced characteristics that link them to primates. Although recent genetic studies strongly support the monophyly of bats, debate continues as to the meaning of available genetic and morphological evidence.

 

Genetic evidence indicates that megabats originated during the early Eocene and should be placed within the four major lines of microbats.

 

Consequently, two new suborders based on molecular data have been proposed. The new suborder of Yinpterochiroptera includes the Pteropodidae, or megabat family, as well as the Rhinolophidae, Hipposideridae, Craseonycteridae, Megadermatidae, and Rhinopomatidae families The other new suborder, Yangochiroptera, includes all of the remaining families of bats (all of which use laryngeal echolocation). These two new suborders are strongly supported by statistical tests. Teeling (2005) found 100% bootstrap support in all maximum likelihood analyses for the division of Chiroptera into these two modified suborders. This conclusion is further supported by a 15-base-pair deletion in BRCA1 and a seven-base-pair deletion in PLCB4 present in all Yangochiroptera and absent in all Yinpterochiroptera. Perhaps most convincingly, a phylogenomic study by Tsagkogeorga et al (2013) showed that the two new proposed suborders were supported by analyses of thousands of genes.

 

The chiropteran phylogeny based on molecular evidence is controversial because microbat paraphyly implies that one of two seemingly unlikely hypotheses occurred. The first suggests that laryngeal echolocation evolved twice in Chiroptera, once in Yangochiroptera and once in the rhinolophoids. The second proposes that laryngeal echolocation had a single origin in Chiroptera, was subsequently lost in the family Pteropodidae (all megabats), and later evolved as a system of tongue-clicking in the genus Rousettus.

 

Analyses of the sequence of the "vocalization" gene, FoxP2, were inconclusive as to whether laryngeal echolocation was secondarily lost in the pteropodids or independently gained in the echolocating lineages. However, analyses of the "hearing" gene, Prestin seemed to favor the independent gain in echolocating species rather than a secondary loss in the pteropodids.

 

In addition to Yinpterochiroptera and Yangochiroptera, the names Pteropodiformes and Vespertilioniformes have also been proposed for these suborders. Under this new proposed nomenclature, the suborder Pteropodiformes includes all extant bat families more closely related to the genus Pteropus than the genus Vespertilio, while the suborder Vespertilioniformes includes all extant bat families more closely related to the genus Vespertilio than to the genus Pteropus.

 

Little fossil evidence is available to help map the evolution of bats, since their small, delicate skeletons do not fossilize very well. However, a Late Cretaceous tooth from South America resembles that of an early microchiropteran bat. Most of the oldest known, definitely identified bat fossils were already very similar to modern microbats. These fossils, Icaronycteris, Archaeonycteris, Palaeochiropteryx and Hassianycteris, are from the early Eocene period, 52.5 million years ago. Archaeopteropus, formerly classified as the earliest known megachiropteran, is now classified as a microchiropteran.

 

Bats were formerly grouped in the superorder Archonta, along with the treeshrews (Scandentia), colugos (Dermoptera), and the primates, because of the apparent similarities between Megachiroptera and such mammals. Genetic studies have now placed bats in the superorder Laurasiatheria, along with carnivorans, pangolins, odd-toed ungulates, even-toed ungulates, and cetaceans. A recent study by Zhang et al. places Chiroptera as a sister taxon to the clade Perissodactyla (which includes horses and other odd-toed ungulates). However, the first phylogenomic analysis of bats shows that they are not sisters to Perissodactyla, instead they are sisters to a larger group that includes ungulates and carnivores.

 

Megabats primarily eat fruit or nectar. In New Guinea, they are likely to have evolved for some time in the absence of microbats, which has resulted in some smaller megabats of the genus Nyctimene becoming (partly) insectivorous to fill the vacant microbat ecological niche. Furthermore, some evidence indicates that the fruit bat genus Pteralopex from the Solomon Islands, and its close relative Mirimiri from Fiji, have evolved to fill some niches that were open because there are no nonvolant or nonflying mammals on those islands.

 

FOSSIL BATS

Fossilized remains of bats are few, as they are terrestrial and light-boned. Only an estimated 12% of the bat fossil record is complete at the genus level. Fossil remains of an Eocene bat, Icaronycteris, were found in 1960. Another Eocene bat, Onychonycteris finneyi, was found in the 52-million-year-old Green River Formation in Wyoming, United States, in 2003. This intermediate fossil has helped to resolve a long-standing disagreement regarding whether flight or echolocation developed first in bats. The shape of the rib cage, faceted infraspious fossa of the scapula, manus morphology, robust clavicle, and keeled sternum all indicated Onychonycteris was capable of powered flight. However, the well-preserved skeleton showed that the small cochlea of the inner ear did not have the morphology necessary to echolocate. O. finneyi lacked an enlarged orbical apophysis on the malleus, and a stylohyal element with an expanded paddle-like cranial tip - both of which are characteristics linked to echolocation in other prehistoric and extant bat species. Because of these absences, and the presence of characteristics necessary for flight, Onychonycteris provides strong support for the “flight first” hypothesis in the evolution of flight and echolocation in bats.

 

The appearance and flight movement of bats 52.5 million years ago were different from those of bats today. Onychonycteris had claws on all five of its fingers, whereas modern bats have at most two claws appearing on two digits of each hand. It also had longer hind legs and shorter forearms, similar to climbing mammals that hang under branches such as sloths and gibbons. This palm-sized bat had short, broad wings, suggesting it could not fly as fast or as far as later bat species. Instead of flapping its wings continuously while flying, Onychonycteris likely alternated between flaps and glides while in the air. Such physical characteristics suggest that this bat did not fly as much as modern bats do, rather flying from tree to tree and spending most of its waking day climbing or hanging on the branches of trees. The distinctive features noted on the Onychonycteris fossil also support the claim that mammalian flight most likely evolved in arboreal gliders, rather than terrestrial runners. This model of flight development, commonly known as the "trees-down" theory, implies that bats attained powered flight by taking advantage of height and gravity, rather than relying on running speeds fast enough for a ground-level take off.

 

The mid-Eocene genus Necromantis is one of the earliest examples of bats specialised to hunt vertebrate prey, as well as one of the largest bats of its epoch.

 

HABITATS

Flight has enabled bats to become one of the most widely distributed groups of mammals. Apart from the Arctic, the Antarctic and a few isolated oceanic islands, bats exist all over the world. Bats are found in almost every habitat available on Earth. Different species select different habitats during different seasons, ranging from seasides to mountains and even deserts, but bat habitats have two basic requirements: roosts, where they spend the day or hibernate, and places for foraging. Most temperate species additionally need a relatively warm hibernation shelter. Bat roosts can be found in hollows, crevices, foliage, and even human-made structures, and include "tents" the bats construct by biting leaves.

 

The United States is home to an estimated 45 to 48 species of bats. The three most common species are Myotis lucifugus (little brown bat), Eptesicus fuscus (big brown bat), and Tadarida brasiliensis (Mexican free-tailed bat). The little and the big brown bats are common throughout the northern two-thirds of the country, while the Mexican free-tailed bat is the most common species in the southwest, sometimes even appearing in portions of the Southeast.

 

ANATOMY

WINGS

The finger bones of bats are much more flexible than those of other mammals, owing to their flattened cross-section and to low levels of minerals, such as calcium, near their tips. In 2006, Sears et al. published a study that traces the elongation of manual bat digits, a key feature required for wing development, to the upregulation of bone morphogenetic proteins (Bmps). During embryonic development, the gene controlling Bmp signaling, Bmp2, is subjected to increased expression in bat forelimbs - resulting in the extension of the offspring's manual digits. This crucial genetic alteration helps create the specialized limbs required for volant locomotion. Sears et al. (2006) also studied the relative proportion of bat forelimb digits from several extant species and compared these with a fossil of Lcaronycteris index, an early extinct species from approximately 50 million years ago. The study found no significant differences in relative digit proportion, suggesting that bat wing morphology has been conserved for over 50 million years.The wings of bats are much thinner and consist of more bones than the wings of birds, allowing bats to maneuver more accurately than the latter, and fly with more lift and less drag. By folding the wings in toward their bodies on the upstroke, they save 35 percent energy during flight. The membranes are also delicate, ripping easily; however, the tissue of the bat's membrane is able to regrow, such that small tears can heal quickly. The surface of their wings is equipped with touch-sensitive receptors on small bumps called Merkel cells, also found on human fingertips. These sensitive areas are different in bats, as each bump has a tiny hair in the center, making it even more sensitive and allowing the bat to detect and collect information about the air flowing over its wings, and to fly more efficiently by changing the shape of its wings in response. An additional kind of receptor cell is found in the wing membrane of species that use their wings to catch prey. This receptor cell is sensitive to the stretching of the membrane. The cells are concentrated in areas of the membrane where insects hit the wings when the bats capture them.

 

OTHER

The teeth of microbats resemble insectivorans. They are very sharp to bite through the hardened armor of insects or the skin of fruit.

 

Mammals have one-way valves in their veins to prevent the blood from flowing backwards, but bats also have one-way valves in their arteries.

 

The tube-lipped nectar bat (Anoura fistulata) has the longest tongue of any mammal relative to its body size. This is beneficial to them in terms of pollination and feeding. Their long, narrow tongues can reach deep into the long cup shape of some flowers. When the tongue retracts, it coils up inside its rib cage.

 

Bats possess highly adapted lung systems to cope with the pressures of powered-flight. Flight is an energetically taxing aerobic activity and requires large amounts of oxygen to be sustained. In bats, the relative alveolar surface area and pulmonary capillary blood volume are significantly larger than most other small quadrupedal mammals.

 

ECHOLOCATION

Bat echolocation is a perceptual system where ultrasonic sounds are emitted specifically to produce echoes. By comparing the outgoing pulse with the returning echoes, the brain and auditory nervous system can produce detailed images of the bat's surroundings. This allows bats to detect, localize, and even classify their prey in complete darkness. At 130 decibels in intensity, bat calls are some of the most intense, airborne animal sounds.

 

To clearly distinguish returning information, bats must be able to separate their calls from the echoes that they receive. Microbats use two distinct approaches.

 

Low duty cycle echolocation: Bats can separate their calls and returning echoes by time. Bats that use this approach time their short calls to finish before echoes return. This is important because these bats contract their middle ear muscles when emitting a call, so they can avoid deafening themselves. The time interval between the call and echo allows them to relax these muscles, so they can clearly hear the returning echo. The delay of the returning echoes provides the bat with the ability to estimate the range to their prey.

 

High duty cycle echolocation: Bats emit a continuous call and separate pulse and echo in frequency. The ears of these bats are sharply tuned to a specific frequency range. They emit calls outside of this range to avoid self-deafening. They then receive echoes back at the finely tuned frequency range by taking advantage of the Doppler shift of their motion in flight. The Doppler shift of the returning echoes yields information relating to the motion and location of the bat's prey. These bats must deal with changes in the Doppler shift due to changes in their flight speed. They have adapted to change their pulse emission frequency in relation to their flight speed so echoes still return in the optimal hearing range.

 

The new Yinpterochiroptera and Yangochiroptera classification of bats, supported by molecular evidence, suggests two possibilities for the evolution of echolocation. It may have been gained once in a common ancestor of all bats and was then subsequently lost in the Old World fruit bats, only to be regained in the horseshoe bats, or echolocation evolved independently in both the Yinpterochiroptera and Yangochiroptera lineages.

 

Two groups of moths exploit a bat sense to echolocate: tiger moths produce ultrasonic signals to warn the bats that they (the moths) are chemically protected or aposematic, other moth species produce signals to jam bat echolocation. Many moth species have a hearing organ called a tympanum, which responds to an incoming bat signal by causing the moth's flight muscles to twitch erratically, sending the moth into random evasive maneuvers.

 

In addition to echolocating prey, bat ears are sensitive to the fluttering of moth wings, the sounds produced by tymbalate insects, and the movement of ground-dwelling prey, such as centipedes, earwigs, etc. The complex geometry of ridges on the inner surface of bat ears helps to sharply focus not only echolocation signals, but also to passively listen for any other sound produced by the prey. These ridges can be regarded as the acoustic equivalent of a Fresnel lens, and may be seen in a large variety of unrelated animals, such as the aye-aye, lesser galago, bat-eared fox, mouse lemur, and others.

 

By repeated scanning, bats can mentally construct an accurate image of the environment in which they are moving and of their prey item.

 

OTHER SENSES

Although the eyes of most microbat species are small and poorly developed, leading to poor visual acuity, no species is blind. Microbats use vision to navigate, especially for long distances when beyond the range of echolocation, and species that are gleaners - that is, ones that attempt to swoop down from above to ambush tasty insects like crickets on the ground or moths up a tree - often have eyesight about as good as a rat's. Some species have been shown to be able to detect ultraviolet light, and most cave dwelling species have developed the ability to utilize very dim light. They also have high-quality senses of smell and hearing. Bats hunt at night, reducing competition with birds, minimizing contact with certain predators, and travel large distances (up to 800 km) in their search for food. Megabat species often have excellent eyesight as good as, if not better than, human vision; they need this for the warm climates they live in and the very social world they occupy, where relations and friends need to be distinguished from other bats in the colony. This eyesight is, unlike its microbat relations, adapted to both night and daylight vision and enables the bat to have some colour vision whereas the microbat sees in blurred shades of grey.

 

BEHAVIOUR

Most microbats are nocturnal and are active at twilight. A large portion of bats migrate hundreds of kilometres to winter hibernation dens, while some pass into torpor in cold weather, rousing and feeding when warm weather allows for insects to be active. Others retreat to caves for winter and hibernate for six months. Bats rarely fly in rain, as the rain interferes with their echolocation, and they are unable to locate their food.

 

The social structure of bats varies, with some leading solitary lives and others living in caves colonized by more than a million bats. The fission-fusion social structure is seen among several species of bats. The term "fusion" refers to a large numbers of bats that congregate in one roosting area, and "fission" refers to breaking up and the mixing of subgroups, with individual bats switching roosts with others and often ending up in different trees and with different roostmates.

 

Studies also show that bats make all kinds of sounds to communicate with others. Scientists in the field have listened to bats and have been able to associate certain sounds with certain behaviours that bats make after the sounds are made.

 

Insectivores make up 70% of bat species and locate their prey by means of echolocation. Of the remainder, most feed on fruits. Only three species sustain themselves with blood.

 

Some species even prey on vertebrates. The leaf-nosed bats (Phyllostomidae) of Central America and South America, and the two bulldog bat (Noctilionidae) species feed on fish. At least two species of bat are known to feed on other bats: the spectral bat, also known as the American false vampire bat, and the ghost bat of Australia. One species, the greater noctule bat, catches and eats small birds in the air.

 

Predators of bats include bat hawks, bat falcons and even spiders.

 

REPRODUCTION

Most bats have a breeding season, which is in the spring for species living in a temperate climate. Bats may have one to three litters in a season, depending on the species and on environmental conditions, such as the availability of food and roost sites. Females generally have one offspring at a time, which could be a result of the mother's need to fly to feed while pregnant. Female bats nurse their young until they are nearly adult size, because a young bat cannot forage on its own until its wings are fully developed.

 

Female bats use a variety of strategies to control the timing of pregnancy and the birth of young, to make delivery coincide with maximum food ability and other ecological factors. Females of some species have delayed fertilization, in which sperm is stored in the reproductive tract for several months after mating. In many such cases, mating occurs in the fall, and fertilization does not occur until the following spring. Other species exhibit delayed implantation, in which the egg is fertilized after mating, but remains free in the reproductive tract until external conditions become favorable for giving birth and caring for the offspring.

 

In yet another strategy, fertilization and implantation both occur, but development of the fetus is delayed until favorable conditions prevail, during the delayed development the mother still gives the fertilized egg nutrients, and oxygenated blood to keep it alive. However, this process can go for a long period of time, because of the advanced gas exchange system. All of these adaptations result in the pup being born during a time of high local production of fruit or insects.

 

At birth, the wings are too small to be used for flight. Young microbats become independent at the age of six to eight weeks, while megabats do not until they are four months old.

 

LIFE EXPECTANCY

A single bat can live over 20 years, but bat population growth is limited by the slow birth rate.

 

HUNTING, FEEDING AND DRINKING

Newborn bats rely on the milk from their mothers. When they are a few weeks old, bats are expected to fly and hunt on their own. It is up to them to find and catch their prey, along with satisfying their thirst.

 

HUNTING

Most bats are nocturnal creatures. Their daylight hours are spent grooming and sleeping; they hunt during the night. The means by which bats navigate while finding and catching their prey in the dark was unknown until the 1790s, when Lazzaro Spallanzani conducted a series of experiments on a group of blind bats. These bats were placed in a room in total darkness, with silk threads strung across the room. Even then, the bats were able to navigate their way through the room. Spallanzani concluded the bats were not using their eyes to fly through complete darkness, but something else.

 

Spallanzani decided the bats were able to catch and find their prey through the use of their ears. To prove this theory, Spallanzani plugged the ears of the bats in his experiment. To his pleasure, he found that the bats with plugged ears were not able to fly with the same amount of skill and precision as they were able to without their ears plugged. Unfortunately for Spallanzani, the twin concepts of sound waves and acoustics would not be understood for another century and he could not explain why specifically the bats were crashing into walls and the threads that he'd strung up around the room, and because of the methodology Spallanzani used, many of his test subjects died.

 

It was thus well known through the nineteenth century that the chiropteran ability to navigate had something to do with hearing, but how they accomplish this was not proven conclusively until the 1930s, by Donald R. Griffin, a biology student at Harvard University. Using a locally native species, the little brown bat, he discovered that bats use echolocation to locate and catch their prey. When bats fly, they produce a constant stream of high-pitched sounds. When the sound waves produced by these sounds hit an insect or other animal, the echoes bounce back to the bat, and guide them to the source.

 

FEEDING AND DIET

The majority of food consumed by bats includes insects, fruits and flower nectar, vertebrates and blood. Almost three-fourths of the world's bats are insect eaters. Bats consume both aerial and ground-dwelling insects. Each bat is typically able to consume one-third of its body weight in insects each night, and several hundred insects in a few hours. This means that a group of a thousand bats could eat four tons of insects each year. If bats were to become extinct, it has been calculated that the insect population would reach an alarmingly high number.

 

VITAMIN C

In a test of 34 bat species from six major families of bats, including major insect- and fruit-eating bat families, all were found to have lost the ability to synthesize vitamin C, and this loss may derive from a common bat ancestor, as a single mutation. However, recent results show that there are at least two species of bat, the frugivorous bat (Rousettus leschenaultii) and insectivorous bat (Hipposideros armiger), that have retained their ability to produce vitamin C. In fact, the whole Chiroptera are in the process of losing the ability to synthesize Vc which most of them have already lost.

 

AERIAL INSECTIVORES

Watching a bat catch and eat an insect is difficult. The action is so fast that all one sees is a bat rapidly change directions, and continue on its way. Scientist Frederick A. Webster discovered how bats catch their prey. In 1960, Webster developed a high-speed camera that was able to take one thousand pictures per second. These photos revealed the fast and precise way in which bats catch insects. Occasionally, a bat will catch an insect in mid-air with its mouth, and eat it in the air. However, more often than not, a bat will use its tail membrane or wings to scoop up the insect and trap it in a sort of "bug net". Then, the bat will take the insect back to its roost. There, the bat will proceed to eat said insect, often using its tail membrane as a kind of napkin, to prevent its meal from falling to the ground. One common insect prey is Helicoverpa zea, a moth that causes major agricultural damage.

 

FORAGE GLEANERS

These bats typically fly down and grasp their prey off the ground with their teeth, and take it to a nearby perch to eat it. Generally, these bats do not use echolocation to locate their prey. Instead, they rely on the sounds produced by the insects. Some make unique sounds, and almost all make some noise while moving through the environment.

 

FRUITS AND FLOWER NECTAR

Fruit eating, or frugivory, is a specific habit found in two families of bats. Megachiropterans and microchiropterans both include species of bat that feed on fruits. These bats feed on the juices of sweet fruits, and fulfill the needs of some seeds to be dispersed. The fruits preferred by most fruit-eating bats are fleshy and sweet, but not particularly strong smelling or colorful. To get the juice of these fruits, bats pull the fruit off the trees with their teeth, and fly back to their roosts with the fruit in their mouths. There, the bats will consume the fruit in a specific way. To do this, the bats crush open the fruit and eat the parts that satisfy their hunger. The remainder of the fruit, the seeds and pulp, are spat onto the ground. These seeds take root and begin to grow into new fruit trees. Over 150 types of plants depend on bats in order to reproduce.Some bats prefer the nectar of flowers to insects or other animals. These bats have evolved specifically for this purpose. For example, these bats possess long muzzles and long, extensible tongues covered in fine bristles that aid them in feeding on particular flowers and plants.[68] When they sip the nectar from these flowers, pollen gets stuck to their fur, and is dusted off when the bats take flight, thus pollinating the plants below them. The rainforest is said to be the most benefitted of all the biomes where bats live, because of the large variety of appealing plants. Because of their specific eating habits, nectar-feeding bats are more prone to extinction than any other type of bat. However, bats benefit from eating fruits and nectar just as much as from eating insects.

 

VERTEBRATES

A small group of carnivorous bats feed on other vertebrates and are considered the top carnivores of the bat world. These bats typically eat a variety of animals, but normally consume frogs, lizards, birds, and sometimes other bats. For example, one vertebrate predator, Trachops cirrhosus, is particularly skilled at catching frogs. These bats locate large groups of frogs by distinguishing their mating calls from other sounds around them. They follow the sounds to the source and pluck them from the surface of the water with their sharp canine teeth. Another example is the greater noctule bat, which is believed to catch birds on the wing.

 

Also, several species of bat feed on fish. These types of bats are found on almost all continents. They use echolocation to detect tiny ripples in the water's surface to locate fish. From there, the bats swoop down low, inches from the water, and use specially enlarged claws on their hind feet to grab the fish out of the water. The bats then take the fish to a feeding roost and consume the animal.

 

BLOOD

A few species of bats exclusively consume blood as their diet. This type of diet is referred to as hematophagy, and three species of bats exhibit this behavior. These species are the common, the white-winged, and the hairy-legged vampire bats. The common vampire bat typically consumes the blood of mammals, while the hairy-legged and white-winged vampires feed on the blood of birds. These species live only in Mexico, Central, and South America, with a presence also on the Island of Trinidad.

 

DEFECATION

Bat dung, or guano, is so rich in nutrients that it is mined from caves, bagged, and used by farmers to fertilize their crops. During the U.S. Civil War, guano was used to make gunpowder.

 

To survive hibernation months, some species build up large reserves of body fat, both as fuel and as insulation.

 

DRINKING

In 1960, Frederic A. Webster discovered bats' method of drinking water using a high-speed camera and flashgun that could take 1,000 photos per second. Webster's camera captured a bat skimming the surface of a body of water, and lowering its jaw to get just one drop of water. It then skimmed again to get a second drop of water, and so on, until it has had its fill. A bat's precision and control during flight is very fine, and it almost never misses. Other bats, such as the flying fox or fruit bat, gently skim the water's surface, then land nearby to lick water from chest fur.

 

WIKIPEDIA

A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος anisos, "unequal" and πτερόν pteron, "wing", because the hindwing is broader than the forewing). Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Dragonflies can be mistaken for the related group, damselflies (Zygoptera), which are similar in structure, though usually lighter in build; however, the wings of most dragonflies are held flat and away from the body, while damselflies hold their wings folded at rest, along or above the abdomen. Dragonflies are agile fliers, while damselflies have a weaker, fluttery flight. Many dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each.

 

Fossils of very large dragonfly-like insects, sometimes called griffinflies, are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in), but were only distant ancestors, not true dragonflies. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threatens dragonfly populations around the world.

 

Dragonflies are predators, both in their aquatic nymphs stage (also known as naiads) and as adults. In some species, the nymphal stage lasts for up to five years, and the adult stage may be as long as ten weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. They are fast, agile fliers, sometimes migrating across oceans, and often live near water. They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, and sperm competition. During mating, the male grasps the female at the back of the head, and the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture.

 

Dragonflies are represented in human culture on artefacts such as pottery, rock paintings, statues and Art Nouveau jewellery. They are used in traditional medicine in Japan and China, and caught for food in Indonesia. They are symbols of courage, strength, and happiness in Japan, but seen as sinister in European folklore. Their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates.

   

Evolution

 

Dragonflies and their relatives are similar in structure to an ancient group, meganisoptera, from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that ever lived, Meganeuropsis permiana from the Early Permian, with a wingspan around 750 mm (30 in);. Known informally as "griffinflies", their fossil record ends with the Permian–Triassic extinction event (about 247 Mya). The Protanisoptera, another ancestral group that lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, and are known from fossil wings from current-day United States, Russia, and Australia, suggesting they might have been cosmopolitan in distribution. While both of those groups are sometimes referred to as "giant dragonflies", in fact true dragonflies/odonata are more modern insects that had not evolved yet.

 

Modern dragonflies do retain some traits of their distant predecessors, and are in a group known as palaeoptera, ancient-winged. They, like the gigantic pre-dinosaur griffinflies, lack the ability to fold their wings up against their bodies in the way modern insects do, although some evolved their own different way to do so. The forerunners of modern Odonata are included in a clade called the Panodonata, which include the basal Zygoptera (damselflies) and the Anisoptera (true dragonflies). Today, some 3,000 species are extant around the world.

 

The relationships of anisopteran families are not fully resolved as of 2013, but all the families are monophyletic except the Corduliidae; the Gomphidae are a sister taxon to all other Anisoptera, the Austropetaliidae are sister to the Aeshnoidea, and the Chlorogomphidae are sister to a clade that includes the Synthemistidae and Libellulidae. On the cladogram, dashed lines indicate unresolved relationships; English names are given (in parentheses)

   

Distribution and diversity

 

About 3,012 species of dragonflies were known in 2010; these are classified into 348 genera in 11 families. The distribution of diversity within the biogeographical regions are summarized below (the world numbers are not ordinary totals, as overlaps in species occur).

 

Dragonflies live on every continent except Antarctica. In contrast to the damselflies (Zygoptera), which tend to have restricted distributions, some genera and species are spread across continents. For example, the blue-eyed darner Rhionaeschna multicolor lives all across North America, and in Central America; emperors Anax live throughout the Americas from as far north as Newfoundland to as far south as Bahia Blanca in Argentina, across Europe to central Asia, North Africa, and the Middle East. The globe skimmer Pantala flavescens is probably the most widespread dragonfly species in the world; it is cosmopolitan, occurring on all continents in the warmer regions. Most Anisoptera species are tropical, with far fewer species in temperate regions.

 

Some dragonflies, including libellulids and aeshnids, live in desert pools, for example in the Mojave Desert, where they are active in shade temperatures between 18 and 45 °C (64.4 to 113 °F); these insects were able to survive body temperatures above the thermal death point of insects of the same species in cooler places.

 

Dragonflies live from sea level up to the mountains, decreasing in species diversity with altitude. Their altitudinal limit is about 3700 m, represented by a species of Aeshna in the Pamirs.

 

Dragonflies become scarce at higher latitudes. They are not native to Iceland, but individuals are occasionally swept in by strong winds, including a Hemianax ephippiger native to North Africa, and an unidentified darter species. In Kamchatka, only a few species of dragonfly including the treeline emerald Somatochlora arctica and some aeshnids such as Aeshna subarctica are found, possibly because of the low temperature of the lakes there. The treeline emerald also lives in northern Alaska, within the Arctic Circle, making it the most northerly of all dragonflies.

   

General description

 

Dragonflies (suborder Anisoptera) are heavy-bodied, strong-flying insects that hold their wings horizontally both in flight and at rest. By contrast, damselflies (suborder Zygoptera) have slender bodies and fly more weakly; most species fold their wings over the abdomen when stationary, and the eyes are well separated on the sides of the head.

 

An adult dragonfly has three distinct segments, the head, thorax, and abdomen, as in all insects. It has a chitinous exoskeleton of hard plates held together with flexible membranes. The head is large with very short antennae. It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of ommatidia, the numbers being greater in the larger species. Aeshna interrupta has 22650 ommatidia of two varying sizes, 4500 being large. The facets facing downward tend to be smaller. Petalura gigantea has 23890 ommatidia of just one size. These facets provide complete vision in the frontal hemisphere of the dragonfly. The compound eyes meet at the top of the head (except in the Petaluridae and Gomphidae, as also in the genus Epiophlebia). Also, they have three simple eyes or ocelli. The mouthparts are adapted for biting with a toothed jaw; the flap-like labrum, at the front of the mouth, can be shot rapidly forward to catch prey. The head has a system for locking it in place that consists of muscles and small hairs on the back of the head that grip structures on the front of the first thoracic segment. This arrester system is unique to the Odonata, and is activated when feeding and during tandem flight.

 

The thorax consists of three segments as in all insects. The prothorax is small and is flattened dorsally into a shield-like disc, which has two transverse ridges. The mesothorax and metathorax are fused into a rigid, box-like structure with internal bracing, and provide a robust attachment for the powerful wing muscles inside. The thorax bears two pairs of wings and three pairs of legs. The wings are long, veined, and membranous, narrower at the tip and wider at the base. The hindwings are broader than the forewings and the venation is different at the base. The veins carry haemolymph, which is analogous to blood in vertebrates, and carries out many similar functions, but which also serves a hydraulic function to expand the body between nymphal stages (instars) and to expand and stiffen the wings after the adult emerges from the final nymphal stage. The leading edge of each wing has a node where other veins join the marginal vein, and the wing is able to flex at this point. In most large species of dragonflies, the wings of females are shorter and broader than those of males. The legs are rarely used for walking, but are used to catch and hold prey, for perching, and for climbing on plants. Each has two short basal joints, two long joints, and a three-jointed foot, armed with a pair of claws. The long leg joints bear rows of spines, and in males, one row of spines on each front leg is modified to form an "eyebrush", for cleaning the surface of the compound eye.

 

The abdomen is long and slender and consists of 10 segments. Three terminal appendages are on segment 10; a pair of superiors (claspers) and an inferior. The second and third segments are enlarged, and in males, on the underside of the second segment has a cleft, forming the secondary genitalia consisting of the lamina, hamule, genital lobe, and penis. There are remarkable variations in the presence and the form of the penis and the related structures, the flagellum, cornua, and genital lobes. Sperm is produced at the 9th segment, and is transferred to the secondary genitalia prior to mating. The male holds the female behind the head using a pair of claspers on the terminal segment. In females, the genital opening is on the underside of the eighth segment, and is covered by a simple flap (vulvar lamina) or an ovipositor, depending on species and the method of egg-laying. Dragonflies having simple flaps shed the eggs in water, mostly in flight. Dragonflies having ovipositors use them to puncture soft tissues of plants and place the eggs singly in each puncture they make.

 

Dragonfly nymphs vary in form with species, and are loosely classed into claspers, sprawlers, hiders, and burrowers. The first instar is known as a prolarva, a relatively inactive stage from which it quickly moults into the more active nymphal form. The general body plan is similar to that of an adult, but the nymph lacks wings and reproductive organs. The lower jaw has a huge, extensible labium, armed with hooks and spines, which is used for catching prey. This labium is folded under the body at rest and struck out at great speed by hydraulic pressure created by the abdominal muscles. Whereas damselfly nymphs have three feathery external gills, dragonfly nymphs have internal gills, located around the fourth and fifth abdominal segments. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails (Gomphidae) that burrow into the sediment, have a snorkel-like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.

   

Colouration

 

Many adult dragonflies have brilliant iridescent or metallic colours produced by structural colouration, making them conspicuous in flight. Their overall colouration is often a combination of yellow, red, brown, and black pigments, with structural colours. Blues are typically created by microstructures in the cuticle that reflect blue light. Greens often combine a structural blue with a yellow pigment. Freshly emerged adults, known as tenerals, are often pale-coloured and obtain their typical colours after a few days, some have their bodies covered with a pale blue, waxy powderiness called pruinosity; it wears off when scraped during mating, leaving darker areas.

 

Some dragonflies, such as the green darner, Anax junius, have a noniridescent blue that is produced structurally by scatter from arrays of tiny spheres in the endoplasmic reticulum of epidermal cells underneath the cuticle.

 

The wings of dragonflies are generally clear, apart from the dark veins and pterostigmata. In the chasers (Libellulidae), however, many genera have areas of colour on the wings: for example, groundlings (Brachythemis) have brown bands on all four wings, while some scarlets (Crocothemis) and dropwings (Trithemis) have bright orange patches at the wing bases. Some aeshnids such as the brown hawker (Aeshna grandis) have translucent, pale yellow wings.

 

Dragonfly nymphs are usually a well-camouflaged blend of dull brown, green, and grey.

   

Biology

 

Ecology

 

Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on tadpoles and small fish. Adults capture insect prey in the air, making use of their acute vision and highly controlled flight. The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilization, and sperm competition.

 

Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.

 

Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements. Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water. Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as Sympetrum (darters) have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there. Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in Aeshna viridis (green hawker), which lives in swamps with the water-soldier, Stratiotes aloides. The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and pH can also affect its use by dragonflies. Most species need moderate conditions, not too eutrophic, not too acidic; a few species such as Sympetrum danae (black darter) and Libellula quadrimaculata (four-spotted chaser) prefer acidic waters such as peat bogs, while others such as Libellula fulva (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.

   

Behaviour

 

Many dragonflies, particularly males, are territorial. Some defend a territory against others of their own species, some against other species of dragonfly and a few against insects in unrelated groups. A particular perch may give a dragonfly a good view over an insect-rich feeding ground; males of many species such as the Pachydiplax longipennis (blue dasher) jostle other dragonflies to maintain the right to alight there. Defending a breeding territory is common among male dragonflies, especially in species that congregate around ponds. The territory contains desirable features such as a sunlit stretch of shallow water, a special plant species, or the preferred substrate for egg-laying. The territory may be small or large, depending on its quality, the time of day, and the number of competitors, and may be held for a few minutes or several hours. Dragonflies including Tramea lacerata (black saddlebags) may notice landmarks that assist in defining the boundaries of the territory. Landmarks may reduce the costs of territory establishment, or might serve as a spatial reference. Some dragonflies signal ownership with striking colours on the face, abdomen, legs, or wings. The Plathemis lydia (common whitetail) dashes towards an intruder holding its white abdomen aloft like a flag. Other dragonflies engage in aerial dogfights or high-speed chases. A female must mate with the territory holder before laying her eggs. There is also conflict between the males and females. Females may sometimes be harassed by males to the extent that it affects their normal activities including foraging and in some dimorphic species females have evolved multiple forms with some forms appearing deceptively like males. In some species females have evolved behavioural responses such as feigning death to escape the attention of males. Similarly, selection of habitat by adult dragonflies is not random, and terrestrial habitat patches may be held for up to 3 months. A species tightly linked to its birth site utilises a foraging area that is several orders of magnitude larger than the birth site.

   

Reproduction

 

Mating in dragonflies is a complex, precisely choreographed process. First, the male has to attract a female to his territory, continually driving off rival males. When he is ready to mate, he transfers a packet of sperm from his primary genital opening on segment 9, near the end of his abdomen, to his secondary genitalia on segments 2–3, near the base of his abdomen. The male then grasps the female by the head with the claspers at the end of his abdomen; the structure of the claspers varies between species, and may help to prevent interspecific mating. The pair flies in tandem with the male in front, typically perching on a twig or plant stem. The female then curls her abdomen downwards and forwards under her body to pick up the sperm from the male's secondary genitalia, while the male uses his "tail" claspers to grip the female behind the head: this distinctive posture is called the "heart" or "wheel"; the pair may also be described as being "in cop".

 

Egg-laying (ovipositing) involves not only the female darting over floating or waterside vegetation to deposit eggs on a suitable substrate, but also the male hovering above her or continuing to clasp her and flying in tandem. The male attempts to prevent rivals from removing his sperm and inserting their own, something made possible by delayed fertilisation and driven by sexual selection. If successful, a rival male uses his penis to compress or scrape out the sperm inserted previously; this activity takes up much of the time that a copulating pair remains in the heart posture. Flying in tandem has the advantage that less effort is needed by the female for flight and more can be expended on egg-laying, and when the female submerges to deposit eggs, the male may help to pull her out of the water.

 

Egg-laying takes two different forms depending on the species. The female in some families has a sharp-edged ovipositor with which she slits open a stem or leaf of a plant on or near the water, so she can push her eggs inside. In other families such as clubtails (Gomphidae), cruisers (Macromiidae), emeralds (Corduliidae), and skimmers (Libellulidae), the female lays eggs by tapping the surface of the water repeatedly with her abdomen, by shaking the eggs out of her abdomen as she flies along, or by placing the eggs on vegetation. In a few species, the eggs are laid on emergent plants above the water, and development is delayed until these have withered and become immersed.

   

Life cycle

 

Dragonflies are hemimetabolous insects; they do not have a pupal stage and undergo an incomplete metamorphosis with a series of nymphal stages from which the adult emerges. Eggs laid inside plant tissues are usually shaped like grains of rice, while other eggs are the size of a pinhead, ellipsoidal, or nearly spherical. A clutch may have as many as 1500 eggs, and they take about a week to hatch into aquatic nymphs or naiads which moult between six and 15 times (depending on species) as they grow. Most of a dragonfly's life is spent as a nymph, beneath the water's surface. The nymph extends its hinged labium (a toothed mouthpart similar to a lower mandible, which is sometimes termed as a "mask" as it is normally folded and held before the face) that can extend forward and retract rapidly to capture prey such as mosquito larvae, tadpoles, and small fish. They breathe through gills in their rectum, and can rapidly propel themselves by suddenly expelling water through the anus. Some naiads, such as the later stages of Antipodophlebia asthenes, hunt on land.

 

The nymph stage of dragonflies lasts up to five years in large species, and between two months and three years in smaller species. When the naiad is ready to metamorphose into an adult, it stops feeding and makes its way to the surface, generally at night. It remains stationary with its head out of the water, while its respiration system adapts to breathing air, then climbs up a reed or other emergent plant, and moults (ecdysis). Anchoring itself firmly in a vertical position with its claws, its skin begins to split at a weak spot behind the head. The adult dragonfly crawls out of its nymph skin, the exuvia, arching backwards when all but the tip of its abdomen is free, to allow its exoskeleton to harden. Curling back upwards, it completes its emergence, swallowing air, which plumps out its body, and pumping haemolymph into its wings, which causes them to expand to their full extent.

 

Dragonflies in temperate areas can be categorized into two groups, an early group and a later one. In any one area, individuals of a particular "spring species" emerge within a few days of each other. The springtime darner (Basiaeschna janata), for example, is suddenly very common in the spring, but disappears a few weeks later and is not seen again until the following year. By contrast, a "summer species" emerges over a period of weeks or months, later in the year. They may be seen on the wing for several months, but this may represent a whole series of individuals, with new adults hatching out as earlier ones complete their lifespans.

   

Sex ratios

 

The sex ratio of male to female dragonflies varies both temporally and spatially. Adult dragonflies have a high male-biased ratio at breeding habitats. The male-bias ratio has contributed partially to the females using different habitats to avoid male harassment. As seen in Hine's emerald dragonfly (Somatochlora hineana), male populations use wetland habitats, while females use dry meadows and marginal breeding habitats, only migrating to the wetlands to lay their eggs or to find mating partners. Unwanted mating is energetically costly for females because it affects the amount of time that they are able to spend foraging.

   

Flight

 

Dragonflies are powerful and agile fliers, capable of migrating across the sea, moving in any direction, and changing direction suddenly. In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, backward, to left and to right. They have four different styles of flight: A number of flying modes are used that include counter-stroking, with forewings beating 180° out of phase with the hindwings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift; phased-stroking, with the hindwings beating 90° ahead of the forewings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking; synchronised-stroking, with forewings and hindwings beating together, is used when changing direction rapidly, as it maximises thrust; and gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.

 

The wings are powered directly, unlike most families of insects, with the flight muscles attached to the wing bases. Dragonflies have a high power/weight ratio, and have been documented accelerating at 4 G linearly and 9 G in sharp turns while pursuing prey.

 

Dragonflies generate lift in at least four ways at different times, including classical lift like an aircraft wing; supercritical lift with the wing above the critical angle, generating high lift and using very short strokes to avoid stalling; and creating and shedding vortices. Some families appear to use special mechanisms, as for example the Libellulidae which take off rapidly, their wings beginning pointed far forward and twisted almost vertically. Dragonfly wings behave highly dynamically during flight, flexing and twisting during each beat. Among the variables are wing curvature, length and speed of stroke, angle of attack, forward/back position of wing, and phase relative to the other wings.

   

Flight speed

 

Old and unreliable claims are made that dragonflies such as the southern giant darner can fly up to 97 km/h (60 mph). However, the greatest reliable flight speed records are for other types of insects. In general, large dragonflies like the hawkers have a maximum speed of 36–54 km/h (22–34 mph) with average cruising speed of about 16 km/h (9.9 mph). Dragonflies can travel at 100 body-lengths per second in forward flight, and three lengths per second backwards.

   

Motion camouflage

 

n high-speed territorial battles between male Australian emperors (Hemianax papuensis), the fighting dragonflies adjust their flight paths to appear stationary to their rivals, minimizing the chance of being detected as they approach.[a] To achieve the effect, the attacking dragonfly flies towards his rival, choosing his path to remain on a line between the rival and the start of his attack path. The attacker thus looms larger as he closes on the rival, but does not otherwise appear to move. Researchers found that six of 15 encounters involved motion camouflage.

   

Temperature control

 

The flight muscles need to be kept at a suitable temperature for the dragonfly to be able to fly. Being cold-blooded, they can raise their temperature by basking in the sun. Early in the morning, they may choose to perch in a vertical position with the wings outstretched, while in the middle of the day, a horizontal stance may be chosen. Another method of warming up used by some larger dragonflies is wing-whirring, a rapid vibration of the wings that causes heat to be generated in the flight muscles. The green darner (Anax junius) is known for its long-distance migrations, and often resorts to wing-whirring before dawn to enable it to make an early start.

 

Becoming too hot is another hazard, and a sunny or shady position for perching can be selected according to the ambient temperature. Some species have dark patches on the wings which can provide shade for the body, and a few use the obelisk posture to avoid overheating. This behaviour involves doing a "handstand", perching with the body raised and the abdomen pointing towards the sun, thus minimising the amount of solar radiation received. On a hot day, dragonflies sometimes adjust their body temperature by skimming over a water surface and briefly touching it, often three times in quick succession. This may also help to avoid desiccation.

   

Feeding

 

Adult dragonflies hunt on the wing using their exceptionally acute eyesight and strong, agile flight. They are almost exclusively carnivorous, eating a wide variety of insects ranging from small midges and mosquitoes to butterflies, moths, damselflies, and smaller dragonflies. A large prey item is subdued by being bitten on the head and is carried by the legs to a perch. Here, the wings are discarded and the prey usually ingested head first. A dragonfly may consume as much as a fifth of its body weight in prey per day. Dragonflies are also some of the insect world's most efficient hunters, catching up to 95% of the prey they pursue.

 

The nymphs are voracious predators, eating most living things that are smaller than they are. Their staple diet is mostly bloodworms and other insect larvae, but they also feed on tadpoles and small fish. A few species, especially those that live in temporary waters, are likely to leave the water to feed. Nymphs of Cordulegaster bidentata sometimes hunt small arthropods on the ground at night, while some species in the Anax genus have even been observed leaping out of the water to attack and kill full-grown tree frogs.

   

Eyesight

 

Dragonfly vision is thought to be like slow motion for humans. Dragonflies see faster than we do; they see around 200 images per second. A dragonfly can see in 360 degrees, and nearly 80 percent of the insect's brain is dedicated to its sight.

   

Predators

 

Although dragonflies are swift and agile fliers, some predators are fast enough to catch them. These include falcons such as the American kestrel, the merlin, and the hobby; nighthawks, swifts, flycatchers and swallows also take some adults; some species of wasps, too, prey on dragonflies, using them to provision their nests, laying an egg on each captured insect. In the water, various species of ducks and herons eat dragonfly nymphs and they are also preyed on by newts, frogs, fish, and water spiders. Amur falcons, which migrate over the Indian Ocean at a period that coincides with the migration of the globe skimmer dragonfly, Pantala flavescens, may actually be feeding on them while on the wing.

   

Parasites

 

Dragonflies are affected by three major groups of parasites: water mites, gregarine protozoa, and trematode flatworms (flukes). Water mites, Hydracarina, can kill smaller dragonfly nymphs, and may also be seen on adults. Gregarines infect the gut and may cause blockage and secondary infection. Trematodes are parasites of vertebrates such as frogs, with complex life cycles often involving a period as a stage called a cercaria in a secondary host, a snail. Dragonfly nymphs may swallow cercariae, or these may tunnel through a nymph's body wall; they then enter the gut and form a cyst or metacercaria, which remains in the nymph for the whole of its development. If the nymph is eaten by a frog, the amphibian becomes infected by the adult or fluke stage of the trematode.

   

Dragonflies and humans

 

Conservation

 

Most odonatologists live in temperate areas and the dragonflies of North America and Europe have been the subject of much research. However, the majority of species live in tropical areas and have been little studied. With the destruction of rainforest habitats, many of these species are in danger of becoming extinct before they have even been named. The greatest cause of decline is forest clearance with the consequent drying up of streams and pools which become clogged with silt. The damming of rivers for hydroelectric schemes and the drainage of low-lying land has reduced suitable habitat, as has pollution and the introduction of alien species.

 

In 1997, the International Union for Conservation of Nature set up a status survey and conservation action plan for dragonflies. This proposes the establishment of protected areas around the world and the management of these areas to provide suitable habitat for dragonflies. Outside these areas, encouragement should be given to modify forestry, agricultural, and industrial practices to enhance conservation. At the same time, more research into dragonflies needs to be done, consideration should be given to pollution control and the public should be educated about the importance of biodiversity.

 

Habitat degradation has reduced dragonfly populations across the world, for example in Japan. Over 60% of Japan's wetlands were lost in the 20th century, so its dragonflies now depend largely on rice fields, ponds, and creeks. Dragonflies feed on pest insects in rice, acting as a natural pest control. Dragonflies are steadily declining in Africa, and represent a conservation priority.

 

The dragonfly's long lifespan and low population density makes it vulnerable to disturbance, such as from collisions with vehicles on roads built near wetlands. Species that fly low and slow may be most at risk.

 

Dragonflies are attracted to shiny surfaces that produce polarization which they can mistake for water, and they have been known to aggregate close to polished gravestones, solar panels, automobiles, and other such structures on which they attempt to lay eggs. These can have a local impact on dragonfly populations; methods of reducing the attractiveness of structures such as solar panels are under experimentation.

   

In culture

 

A blue-glazed faience dragonfly amulet was found by Flinders Petrie at Lahun, from the Late Middle Kingdom of ancient Egypt.

 

Many Native American tribes consider dragonflies to be medicine animals that had special powers. For example, the southwestern tribes, including the Pueblo, Hopi, and Zuni, associated dragonflies with transformation. They referred to dragonflies as "snake doctors" because they believed dragonflies followed snakes into the ground and healed them if they were injured. For the Navajo, dragonflies symbolize pure water. Often stylized in a double-barred cross design, dragonflies are a common motif in Zuni pottery, as well as Hopi rock art and Pueblo necklaces.: 20–26 

 

As a seasonal symbol in Japan, the dragonflies are associated with season of autumn. In Japan, they are symbols of rebirth, courage, strength, and happiness. They are also depicted frequently in Japanese art and literature, especially haiku poetry. Japanese children catch large dragonflies as a game, using a hair with a small pebble tied to each end, which they throw into the air. The dragonfly mistakes the pebbles for prey, gets tangled in the hair, and is dragged to the ground by the weight.: 38 

 

In Chinese culture, dragonflies symbolize both change and instability. They are also symbols in the Chinese practices of Feng Shui, where placements of dragonfly statues and artwork in parts of a home or office are believed to bring new insights and positive changes.

 

In both China and Japan, dragonflies have been used in traditional medicine. In Indonesia, adult dragonflies are caught on poles made sticky with birdlime, then fried in oil as a delicacy.

 

Images of dragonflies are common in Art Nouveau, especially in jewellery designs. They have also been used as a decorative motif on fabrics and home furnishings. Douglas, a British motorcycle manufacturer based in Bristol, named its innovatively designed postwar 350-cc flat-twin model the Dragonfly.

 

Among the classical names of Japan are Akitsukuni (秋津国), Akitsushima (秋津島), Toyo-akitsushima (豊秋津島). Akitsu is an old word for dragonfly, so one interpretation of Akitsushima is "Dragonfly Island". This is attributed to a legend in which Japan's mythical founder, Emperor Jimmu, was bitten by a mosquito, which was then eaten by a dragonfly.

 

In Europe, dragonflies have often been seen as sinister. Some English vernacular names, such as "horse-stinger", "devil's darning needle", and "ear cutter", link them with evil or injury. Swedish folklore holds that the devil uses dragonflies to weigh people's souls.: 25–27  The Norwegian name for dragonflies is Øyenstikker ("eye-poker"), and in Portugal, they are sometimes called tira-olhos ("eyes-snatcher"). They are often associated with snakes, as in the Welsh name gwas-y-neidr, "adder's servant". The Southern United States terms "snake doctor" and "snake feeder" refer to a folk belief that dragonflies catch insects for snakes or follow snakes around and stitch them back together if they are injured. Interestingly, the Hungarian name for dragonfly is szitakötő ("sieve-knitter").

 

The watercolourist Moses Harris (1731–1785), known for his The Aurelian or natural history of English insects (1766), published in 1780, the first scientific descriptions of several Odonata including the banded demoiselle, Calopteryx splendens. He was the first English artist to make illustrations of dragonflies accurate enough to be identified to species (Aeshna grandis at top left of plate illustrated), though his rough drawing of a nymph (at lower left) with the mask extended appears to be plagiarised.[b]

 

More recently, dragonfly watching has become popular in America as some birdwatchers seek new groups to observe.

 

In heraldry, like other winged insects, the dragonfly is typically depicted tergiant (with its back facing the viewer), with its head to chief.

   

In poetry and literature

 

Lafcadio Hearn wrote in his 1901 book A Japanese Miscellany that Japanese poets had created dragonfly haiku "almost as numerous as are the dragonflies themselves in the early autumn." The poet Matsuo Bashō (1644–1694) wrote haiku such as "Crimson pepper pod / add two pairs of wings, and look / darting dragonfly", relating the autumn season to the dragonfly. Hori Bakusui (1718–1783) similarly wrote "Dyed he is with the / Colour of autumnal days, / O red dragonfly."

 

The poet Lord Tennyson, described a dragonfly splitting its old skin and emerging shining metallic blue like "sapphire mail" in his 1842 poem "The Two Voices", with the lines "An inner impulse rent the veil / Of his old husk: from head to tail / Came out clear plates of sapphire mail."

 

The novelist H. E. Bates described the rapid, agile flight of dragonflies in his 1937 nonfiction book Down the River:

 

I saw, once, an endless procession, just over an area of water-lilies, of small sapphire dragonflies, a continuous play of blue gauze over the snowy flowers above the sun-glassy water. It was all confined, in true dragonfly fashion, to one small space. It was a continuous turning and returning, an endless darting, poising, striking and hovering, so swift that it was often lost in sunlight.

 

In technology

 

A dragonfly has been genetically modified with light-sensitive "steering neurons" in its nerve cord to create a cyborg-like "DragonflEye". The neurons contain genes like those in the eye to make them sensitive to light. Miniature sensors, a computer chip and a solar panel were fitted in a "backpack" over the insect's thorax in front of its wings. Light is sent down flexible light-pipes named optrodes[c] from the backpack into the nerve cord to give steering commands to the insect. The result is a "micro-aerial vehicle that's smaller, lighter and stealthier than anything else that's manmade".

 

[Credit: en.wikipedia.org/]

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