Comparison Between I Have No Mouth, And I Must Scream

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Comparison Between I Have No Mouth, And I Must Scream



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I Have No Mouth and I Must Scream - The End of the Apocalypse - Extra Sci Fi

Notable not only for the fact that Ellison had a heavy hand in the writing and development of the game, but he himself actually served as the voice actor for the supercomputer AM, marking one of the very few acting credits on his resume. Failing the final level of the game will result in the player character of choice being rewarded with the same fate as the protagonist of the original novel: transformed into a hideous slug-like monster and left at AM's mercy for all time. Example of: And I Must Scream. Community Showcase More. Follow TV Tropes. You need to login to do this. Get Known if you don't have an account.

Let me come to tell you how much I've come to hate you since I began to live. There are We will never end! We have no beginning, so we can have no end! We will return! Don't you understand? We are humanity! We are YOU! In one form, in another form, we are always with you! You can't protect yourself because we come in many, many guises. We shall return! The irises of the southern toad Anaxyrus terrestris are patterned so as to blend in with the surrounding camouflaged skin. The distant vision of a frog is better than its near vision. Calling frogs will quickly become silent when they see an intruder or even a moving shadow but the closer an object is, the less well it is seen.

Frogs can hear both in the air and below water. They do not have external ears ; the eardrums tympanic membranes are directly exposed or may be covered by a layer of skin and are visible as a circular area just behind the eye. The size and distance apart of the eardrums is related to the frequency and wavelength at which the frog calls. In some species such as the bullfrog, the size of the tympanum indicates the sex of the frog; males have tympani that are larger than their eyes while in females, the eyes and tympani are much the same size. The middle ear contains semicircular canals which help control balance and orientation.

In the inner ear, the auditory hair cells are arranged in two areas of the cochlea, the basilar papilla and the amphibian papilla. The former detects high frequencies and the latter low frequencies. In some species that inhabit arid regions, the sound of thunder or heavy rain may arouse them from a dormant state. The call or croak of a frog is unique to its species. Frogs create this sound by passing air through the larynx in the throat. In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth, that distend during the amplification of the call.

Some frog calls are so loud that they can be heard up to a mile away. Frogs in the genera Heleioporus and Neobatrachus lack vocal sacs but can still produce a loud call. Their buccal cavity is enlarged and dome-shaped, acting as a resonance chamber that amplifies the sound. Species of frog that lack vocal sacs and that do not have a loud call tend to inhabit areas close to constantly noisy, flowing water.

They need to use an alternative means to communicate. The coastal tailed frog Ascaphus truei lives in mountain streams in North America and does not vocalize. The main reason for calling is to allow male frogs to attract a mate. Males may call individually or there may be a chorus of sound where numerous males have converged on breeding sites. Females of many frog species, such as the common tree frog Polypedates leucomystax , reply to the male calls, which acts to reinforce reproductive activity in a breeding colony. The rationale for this is thought to be that by demonstrating his prowess, the male shows his fitness to produce superior offspring.

A different call is emitted by a male frog or unreceptive female when mounted by another male. This is a distinct chirruping sound and is accompanied by a vibration of the body. All of these calls are emitted with the mouth of the frog closed. It is typically used when the frog has been grabbed by a predator and may serve to distract or disorient the attacker so that it releases the frog. Many species of frog have deep calls. The croak of the American bullfrog Rana catesbiana is sometimes written as "jug o' rum".

The males are notable for their varieties of calls where upward and downward frequency modulations take place. When they communicate, they produce calls that fall in the ultrasound frequency range. The last aspect that makes this species of frog's calls unusual is that nonlinear acoustic phenomena are important components in their acoustic signals. During extreme conditions, some frogs enter a state of torpor and remain inactive for months. In colder regions, many species of frog hibernate in winter. Those that live on land such as the American toad Bufo americanus dig a burrow and make a hibernaculum in which to lie dormant. Others, less proficient at digging, find a crevice or bury themselves in dead leaves.

Aquatic species such as the American bullfrog Rana catesbeiana normally sink to the bottom of the pond where they lie, semi-immersed in mud but still able to access the oxygen dissolved in the water. Their metabolism slows down and they live on their energy reserves. Some frogs such as the wood frog or spring peeper can even survive being frozen. Ice crystals form under the skin and in the body cavity but the essential organs are protected from freezing by a high concentration of glucose. An apparently lifeless, frozen frog can resume respiration and its heartbeat can restart when conditions warm up. At the other extreme, the striped burrowing frog Cyclorana alboguttata regularly aestivates during the hot, dry season in Australia, surviving in a dormant state without access to food and water for nine or ten months of the year.

It burrows underground and curls up inside a protective cocoon formed by its shed skin. Researchers at the University of Queensland have found that during aestivation, the metabolism of the frog is altered and the operational efficiency of the mitochondria is increased. This means that the limited amount of energy available to the comatose frog is used in a more efficient manner. This survival mechanism is only useful to animals that remain completely unconscious for an extended period of time and whose energy requirements are low because they are cold-blooded and have no need to generate heat.

Different species of frog use a number of methods of moving around including jumping , running , walking , swimming , burrowing , climbing and gliding. Frogs are generally recognized as exceptional jumpers and, relative to their size, the best jumpers of all vertebrates. Within a species, jump distance increases with increasing size, but relative jumping distance body-lengths jumped decreases.

The Indian skipper frog Euphlyctis cyanophlyctis has the ability to leap out of the water from a position floating on the surface. Slow-motion photography shows that the muscles have passive flexibility. They are first stretched while the frog is still in the crouched position, then they are contracted before being stretched again to launch the frog into the air. The fore legs are folded against the chest and the hind legs remain in the extended, streamlined position for the duration of the jump.

When the muscles contract, the energy is first transferred into the stretched tendon which is wrapped around the ankle bone. Then the muscles stretch again at the same time as the tendon releases its energy like a catapult to produce a powerful acceleration beyond the limits of muscle-powered acceleration. Early hatching of froglets can have negative effects on frog jumping performance and overall locomotion. Frogs in the families Bufonidae, Rhinophrynidae , and Microhylidae have short back legs and tend to walk rather than jump. The Great Plains narrow-mouthed toad Gastrophryne olivacea has been described as having a gait that is "a combination of running and short hops that are usually only an inch or two in length".

By measuring the toad's uptake of oxygen it was found that hopping was an inefficient use of resources during sustained locomotion but was a useful strategy during short bursts of high-intensity activity. The red-legged running frog Kassina maculata has short, slim hind limbs unsuited to jumping. It can move fast by using a running gait in which the two hind legs are used alternately. Slow-motion photography shows, unlike a horse that can trot or gallop, the frog's gait remained similar at slow, medium, and fast speeds. Frogs that live in or visit water have adaptations that improve their swimming abilities.

The hind limbs are heavily muscled and strong. The webbing between the toes of the hind feet increases the area of the foot and helps propel the frog powerfully through the water. Members of the family Pipidae are wholly aquatic and show the most marked specialization. They have inflexible vertebral columns, flattened, streamlined bodies, lateral line systems, and powerful hind limbs with large webbed feet. Some frogs have become adapted for burrowing and a life underground. They tend to have rounded bodies, short limbs, small heads with bulging eyes, and hind feet adapted for excavation. An extreme example of this is the purple frog Nasikabatrachus sahyadrensis from southern India which feeds on termites and spends almost its whole life underground.

It emerges briefly during the monsoon to mate and breed in temporary pools. It has a tiny head with a pointed snout and a plump, rounded body. Because of this fossorial existence, it was first described in , being new to the scientific community at that time, although previously known to local people. The spadefoot toads of North America are also adapted to underground life. The Plains spadefoot toad Spea bombifrons is typical and has a flap of keratinised bone attached to one of the metatarsals of the hind feet which it uses to dig itself backwards into the ground.

As it digs, the toad wriggles its hips from side to side to sink into the loose soil. It has a shallow burrow in the summer from which it emerges at night to forage. In winter, it digs much deeper and has been recorded at a depth of 4. During this time, urea accumulates in its tissues and water is drawn in from the surrounding damp soil by osmosis to supply the toad's needs. The burrowing frogs of Australia have a rather different lifestyle. The western spotted frog Heleioporus albopunctatus digs a burrow beside a river or in the bed of an ephemeral stream and regularly emerges to forage.

Mating takes place and eggs are laid in a foam nest inside the burrow. The eggs partially develop there, but do not hatch until they are submerged following heavy rainfall. The tadpoles then swim out into the open water and rapidly complete their development. One of these, the green burrowing frog Scaphiophryne marmorata , has a flattened head with a short snout and well-developed metatarsal tubercles on its hind feet to help with excavation.

It also has greatly enlarged terminal discs on its fore feet that help it to clamber around in bushes. Tree frogs live high in the canopy , where they scramble around on the branches, twigs, and leaves, sometimes never coming down to earth. The "true" tree frogs belong to the family Hylidae, but members of other frog families have independently adopted an arboreal habit, a case of convergent evolution. These include the glass frogs Centrolenidae , the bush frogs Hyperoliidae , some of the narrow-mouthed frogs Microhylidae , and the shrub frogs Rhacophoridae. The surface of the toe pads is formed from a closely packed layer of flat-topped, hexagonal epidermal cells separated by grooves into which glands secrete mucus.

These toe pads, moistened by the mucus, provide the grip on any wet or dry surface, including glass. The forces involved include boundary friction of the toe pad epidermis on the surface and also surface tension and viscosity. The reticulated leaf frog Phyllomedusa ayeaye has a single opposed digit on each fore foot and two opposed digits on its hind feet. This allows it to grasp the stems of bushes as it clambers around in its riverside habitat. During the evolutionary history of frogs, several different groups have independently taken to the air. Typical of them is Wallace's flying frog Rhacophorus nigropalmatus from Malaysia and Borneo. It has large feet with the fingertips expanded into flat adhesive discs and the digits fully webbed.

Flaps of skin occur on the lateral margins of the limbs and across the tail region. With the digits splayed, the limbs outstretched, and these flaps spread, it can glide considerable distances, but is unable to undertake powered flight. Like other amphibians, the life cycle of a frog normally starts in water with an egg that hatches into a limbless larva with gills, commonly known as a tadpole. After further growth, during which it develops limbs and lungs, the tadpole undergoes metamorphosis in which its appearance and internal organs are rearranged. After this it is able to leave the water as a miniature, air-breathing frog. Direct development , where eggs hatch into juveniles like small adults, is also known in many frogs, for example, Ischnocnema henselii , [] Eleutherodactylus coqui , [] and Raorchestes ochlandrae and Raorchestes chalazodes.

Two main types of reproduction occur in frogs, prolonged breeding and explosive breeding. In the former, adopted by the majority of species, adult frogs at certain times of year assemble at a pond, lake or stream to breed. Many frogs return to the bodies of water in which they developed as larvae. This often results in annual migrations involving thousands of individuals. In explosive breeders, mature adult frogs arrive at breeding sites in response to certain trigger factors such as rainfall occurring in an arid area. In these frogs, mating and spawning take place promptly and the speed of larval growth is rapid in order to make use of the ephemeral pools before they dry up.

Among prolonged breeders, males usually arrive at the breeding site first and remain there for some time whereas females tend to arrive later and depart soon after they have spawned. This means that males outnumber females at the water's edge and defend territories from which they expel other males. They advertise their presence by calling, often alternating their croaks with neighbouring frogs. Larger, stronger males tend to have deeper calls and maintain higher quality territories.

Females select their mates at least partly on the basis of the depth of their voice. They may intercept females that are approaching a calling male or take over a vacated territory. Calling is an energy-sapping activity. Sometimes the two roles are reversed and a calling male gives up its territory and becomes a satellite. In explosive breeders, the first male that finds a suitable breeding location, such as a temporary pool, calls loudly and other frogs of both sexes converge on the pool. Explosive breeders tend to call in unison creating a chorus that can be heard from far away.

The spadefoot toads Scaphiopus spp. Mate selection and courtship is not as important as speed in reproduction. In some years, suitable conditions may not occur and the frogs may go for two or more years without breeding. At the breeding site, the male mounts the female and grips her tightly round the body. Typically, amplexus takes place in the water, the female releases her eggs and the male covers them with sperm; fertilization is external. In many species such as the Great Plains toad Bufo cognatus , the male restrains the eggs with his back feet, holding them in place for about three minutes.

In these species, fertilization is internal and females give birth to fully developed juvenile frogs, except L. Frogs' embryos are typically surrounded by several layers of gelatinous material. When several eggs are clumped together, they are collectively known as frogspawn. The jelly provides support and protection while allowing the passage of oxygen, carbon dioxide and ammonia. It absorbs moisture and swells on contact with water.

After fertilization, the innermost portion liquifies to allow free movement of the developing embryo. In certain species, such as the Northern red-legged frog Rana aurora and the wood frog Rana sylvatica , symbiotic unicellular green algae are present in the gelatinous material. It is thought that these may benefit the developing larvae by providing them with extra oxygen through photosynthesis. The shape and size of the egg mass is characteristic of the species. Ranids tend to produce globular clusters containing large numbers of eggs whereas bufonids produce long, cylindrical strings.

The tiny yellow-striped pygmy eleuth Eleutherodactylus limbatus lays eggs singly, burying them in moist soil. The eggs hatch when the nest is flooded, or the tadpoles may complete their development in the foam if flooding does not occur. Aquatic eggs normally hatch within one week when the capsule splits as a result of enzymes released by the developing larvae. The larvae that emerge from the eggs, known as tadpoles or occasionally polliwogs , typically have oval bodies and long, vertically flattened tails. As a general rule, free-living larvae are fully aquatic, but at least one species Nannophrys ceylonensis has semiterrestrial tadpoles which live among wet rocks.

From early in its development, a gill pouch covers the tadpole's gills and front legs. The lungs soon start to develop and are used as an accessory breathing organ. Some species go through metamorphosis while still inside the egg and hatch directly into small frogs. Tadpoles lack true teeth, but the jaws in most species have two elongated, parallel rows of small, keratinized structures called keradonts in their upper jaws. Their lower jaws usually have three rows of keradonts surrounded by a horny beak, but the number of rows can vary and the exact arrangements of mouth parts provide a means for species identification.

This has been suggested as an adaptation to their lifestyles; because the transformation into frogs happens very fast, the tail is made of soft tissue only, as bone and cartilage take a much longer time to be broken down and absorbed. The tail fin and tip is fragile and will easily tear, which is seen as an adaptation to escape from predators which tries to grasp them by the tail. Tadpoles are typically herbivorous , feeding mostly on algae , including diatoms filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles, and fish. The Cuban tree frog Osteopilus septentrionalis is one of a number of species in which the tadpoles can be cannibalistic. Tadpoles that develop legs early may be eaten by the others, so late developers may have better long-term survival prospects.

Tadpoles are highly vulnerable to being eaten by fish, newts , predatory diving beetles , and birds, such as kingfishers. Some tadpoles, including those of the cane toad Bufo marinus , are poisonous. The tadpole stage may be as short as a week in explosive breeders or it may last through one or more winters followed by metamorphosis in the spring. At the end of the tadpole stage, a frog undergoes metamorphosis in which its body makes a sudden transition into the adult form.

This metamorphosis typically lasts only 24 hours, and is initiated by production of the hormone thyroxine. This causes different tissues to develop in different ways. The principal changes that take place include the development of the lungs and the disappearance of the gills and gill pouch, making the front legs visible. The lower jaw transforms into the big mandible of the carnivorous adult, and the long, spiral gut of the herbivorous tadpole is replaced by the typical short gut of a predator. The eardrum, middle ear, and inner ear are developed. The skin becomes thicker and tougher, the lateral line system is lost, and skin glands are developed. At this time, the tail is being lost and locomotion by means of limbs is only just becoming established.

After metamorphosis, young adults may disperse into terrestrial habitats or continue to live in water. Almost all frog species are carnivorous as adults, preying on invertebrates, including arthropods , worms , snails , and slugs. A few of the larger ones may eat other frogs, small mammals , and fish. Some frogs use their sticky tongues to catch fast-moving prey, while others push food into their mouths with their hands. A few species also eat plant matter; the tree frog Xenohyla truncata is partly herbivorous, its diet including a large proportion of fruit, [] Leptodactylus mystaceus has been found to eat plants, [] [] and folivory occurs in Euphlyctis hexadactylus , with plants constituting The northern leopard frog Rana pipiens is eaten by herons , hawks , fish, large salamanders , snakes , raccoons , skunks , mink , bullfrogs, and other animals.

Frogs are primary predators and an important part of the food web. Being cold-blooded , they make efficient use of the food they eat with little energy being used for metabolic processes, while the rest is transformed into biomass. They are themselves eaten by secondary predators and are the primary terrestrial consumers of invertebrates, most of which feed on plants. By reducing herbivory, they play a part in increasing the growth of plants and are thus part of a delicately balanced ecosystem.

Little is known about the longevity of frogs and toads in the wild, but some can live for many years. Skeletochronology is a method of examining bones to determine age. Using this method, the ages of mountain yellow-legged frogs Rana muscosa were studied, the phalanges of the toes showing seasonal lines where growth slows in winter. The oldest frogs had ten bands, so their age was believed to be 14 years, including the four-year tadpole stage. The cane toad Bufo marinus has been known to survive 24 years in captivity, and the American bullfrog Rana catesbeiana 14 years.

Those that breed in smaller water bodies tend to have greater and more complex parental care behaviour. Once this happened, the desiccating terrestrial environment demands that one or both parents keep them moist to ensure their survival. In small pools, predators are mostly absent and competition between tadpoles becomes the variable that constrains their survival. Certain frog species avoid this competition by making use of smaller phytotelmata water-filled leaf axils or small woody cavities as sites for depositing a few tadpoles. Frog species that changed from the use of larger to smaller phytotelmata have evolved a strategy of providing their offspring with nutritive but unfertilized eggs.

The male frog guards them from predation and carries water in his cloaca to keep them moist. When they hatch, the female moves the tadpoles on her back to a water-holding bromeliad or other similar water body, depositing just one in each location. She visits them regularly and feeds them by laying one or two unfertilized eggs in the phytotelma, continuing to do this until the young are large enough to undergo metamorphosis. Many other diverse forms of parental care are seen in frogs. The tiny male Colostethus subpunctatus stands guard over his egg cluster, laid under a stone or log. When the eggs hatch, he transports the tadpoles on his back to a temporary pool, where he partially immerses himself in the water and one or more tadpoles drop off.

He then moves on to another pool. He keeps them damp in dry weather by immersing himself in a pond, and prevents them from getting too wet in soggy vegetation by raising his hindquarters. After three to six weeks, he travels to a pond and the eggs hatch into tadpoles. The foam is made from proteins and lectins , and seems to have antimicrobial properties. The eggs are laid in the centre, followed by alternate layers of foam and eggs, finishing with a foam capping.

Some frogs protect their offspring inside their own bodies. Both male and female pouched frogs Assa darlingtoni guard their eggs, which are laid on the ground. When the eggs hatch, the male lubricates his body with the jelly surrounding them and immerses himself in the egg mass. The tadpoles wriggle into skin pouches on his side, where they develop until they metamorphose into juvenile frogs. She ceases to feed and stops secreting stomach acid.

The tadpoles rely on the yolks of the eggs for nourishment. After six or seven weeks, they are ready for metamorphosis. The mother regurgitates the tiny frogs, which hop away from her mouth. When the tadpoles are about to hatch, they are engulfed by the male, which carries them around inside his much-enlarged vocal sac. Here they are immersed in a frothy, viscous liquid that contains some nourishment to supplement what they obtain from the yolks of the eggs. They remain in the sac for seven to ten weeks before undergoing metamorphosis, after which they move into the male's mouth and emerge. At first sight, frogs seem rather defenceless because of their small size, slow movement, thin skin, and lack of defensive structures, such as spines, claws or teeth.

Many use camouflage to avoid detection, the skin often being spotted or streaked in neutral colours that allow a stationary frog to merge into its surroundings. Some can make prodigious leaps, often into water, that help them to evade potential attackers, while many have other defensive adaptations and strategies. The skin of many frogs contains mild toxic substances called bufotoxins to make them unpalatable to potential predators. Most toads and some frogs have large poison glands, the parotoid glands , located on the sides of their heads behind the eyes and other glands elsewhere on their bodies. These glands secrete mucus and a range of toxins that make frogs slippery to hold and distasteful or poisonous.

If the noxious effect is immediate, the predator may cease its action and the frog may escape. If the effect develops more slowly, the predator may learn to avoid that species in future. The poison dart frogs in the family Dendrobatidae do this. They are typically red, orange, or yellow, often with contrasting black markings on their bodies. Allobates zaparo is not poisonous, but mimics the appearance of two different toxic species with which it shares a common range in an effort to deceive predators. They "flash" this when attacked, adopting a pose that exposes the vivid colouring on their bellies.

Some frogs, such as the poison dart frogs , are especially toxic. The native peoples of South America extract poison from these frogs to apply to their weapons for hunting, [] although few species are toxic enough to be used for this purpose. At least two non-poisonous frog species in tropical America Eleutherodactylus gaigei and Lithodytes lineatus mimic the colouration of dart poison frogs for self-protection. Many predators of frogs have become adapted to tolerate high levels of these poisons, but other creatures, including humans who handle the frogs, may be severely affected.

Some frogs use bluff or deception. The European common toad Bufo bufo adopts a characteristic stance when attacked, inflating its body and standing with its hindquarters raised and its head lowered. This places the parotoid glands in the most effective position, the other glands on its back begin to ooze noxious secretions and the most vulnerable parts of its body are protected. The gray tree frog Hyla versicolor makes an explosive sound that sometimes repels the shrew Blarina brevicauda.

The strategy employed by juvenile American toads Bufo americanus on being approached by a snake is to crouch down and remain immobile. This is usually successful, with the snake passing by and the toad remaining undetected. If it is encountered by the snake's head, however, the toad hops away before crouching defensively. Frogs live on all the continents except Antarctica, but they are not present on certain islands, especially those far away from continental land masses. Members of the Australian genus Cyclorana bury themselves underground where they create a water-impervious cocoon in which to aestivate during dry periods.

Once it rains, they emerge, find a temporary pool, and breed. Egg and tadpole development is very fast in comparison to those of most other frogs, so breeding can be completed before the pond dries up. The wood frog Rana sylvatica , whose habitat extends into the Arctic Circle , buries itself in the ground during winter. Although much of its body freezes during this time, it maintains a high concentration of glucose in its vital organs, which protects them from damage.

In , of 4, species of amphibians that depend on water during some lifecycle stage, 1, This is likely to be an underestimate because it excludes 1, species for which evidence was insufficient to assess their status. More than one-third of frog species are considered to be threatened with extinction , and more than species are believed to have become extinct since the s. The latter is of particular concern to scientists because it inhabited the pristine Monteverde Cloud Forest Reserve and its population crashed in , along with about 20 other frog species in the area.

This could not be linked directly to human activities, such as deforestation, and was outside the range of normal fluctuations in population size. Many environmental scientists believe amphibians, including frogs, are good biological indicators of broader ecosystem health because of their intermediate positions in food chains, their permeable skins, and typically biphasic lives aquatic larvae and terrestrial adults.

Frog mutations and genetic defects have increased since the s. These often include missing legs or extra legs. Various causes have been identified or hypothesized, including an increase in ultraviolet radiation affecting the spawn on the surface of ponds, chemical contamination from pesticides and fertilizers, and parasites such as the trematode Ribeiroia ondatrae. Probably all these are involved in a complex way as stressors , environmental factors contributing to rates of disease, and vulnerability to attack by parasites.

Malformations impair mobility and the individuals may not survive to adulthood. An increase in the number of frogs eaten by birds may actually increase the likelihood of parasitism of other frogs, because the trematode's complex lifecycle includes the ramshorn snail and several intermediate hosts such as birds. In a few cases, captive breeding programs have been established and have largely been successful.

The cane toad Bufo marinus is a very adaptable species native to South and Central America. In the s, it was introduced into Puerto Rico, and later various other islands in the Pacific and Caribbean region, as a biological pest control agent. Initial results in many of these countries were positive, but it later became apparent that the toads upset the ecological balance in their new environments. They bred freely, competed with native frog species, ate bees and other harmless native invertebrates, had few predators in their adopted habitats, and poisoned pets, carnivorous birds, and mammals.

In many of these countries, they are now regarded both as pests and invasive species , and scientists are looking for a biological method to control them. Frog legs are eaten by humans in many parts of the world. Chinese edible frog and pig frogs are farmed and consumed on a large scale in some areas of China. Frog legs are part of Chinese Sichuan and Cantonese cuisine. In Indonesia , frog-leg soup is known as swikee or swike. Indonesia is the world's largest exporter of frog meat, exporting more than 5, tonnes of frog meat each year, mostly to France, Belgium and Luxembourg.

Originally, they were supplied from local wild populations, but overexploitation led to a diminution in the supply. This resulted in the development of frog farming and a global trade in frogs. The mountain chicken frog , so-called as it tastes of chicken, is now endangered, in part due to human consumption, and was a major food choice of the Dominicans. Coon, possum, partridges, prairie hen, and frogs were among the fare Mark Twain recorded as part of American cuisine. Frogs are used for dissections in high school and university anatomy classes, often first being injected with coloured substances to enhance contrasts among the biological systems.

This practice is declining due to animal welfare concerns, and "digital frogs" are now available for virtual dissection. Frogs have served as experimental animals throughout the history of science. Eighteenth-century biologist Luigi Galvani discovered the link between electricity and the nervous system by studying frogs. Stannius used a frog's heart in a procedure called a Stannius ligature to demonstrate the ventricle and atria beat independently of each other and at different rates. A sample of urine from a pregnant woman injected into a female frog induces it to lay eggs , a discovery made by English zoologist Lancelot Hogben.

This is because a hormone, human chorionic gonadotropin , is present in substantial quantities in the urine of women during pregnancy. King cloned a frog by somatic cell nuclear transfer. This same technique was later used to create Dolly the sheep , and their experiment was the first time a successful nuclear transplantation had been accomplished in higher animals. Frogs are used in cloning research and other branches of embryology.

Although alternative pregnancy tests have been developed, biologists continue to use Xenopus as a model organism in developmental biology because their embryos are large and easy to manipulate, they are readily obtainable, and can easily be kept in the laboratory. Genomes of Xenopus laevis , X. Due to being inexpensive and relatively easy to care for, many species of frogs and toads have become popular as exotic pets , they are undemanding and require low maintenance. Both frogs and toads can be housed in paludariums , terrariums and aquariums. Because frog toxins are extraordinarily diverse, they have raised the interest of biochemists as a "natural pharmacy". The alkaloid epibatidine , a painkiller times more potent than morphine , is made by some species of poison dart frogs.

Other chemicals isolated from the skins of frogs may offer resistance to HIV infection. It has long been suspected that pre-Columbian Mesoamericans used a toxic secretion produced by the cane toad as a hallucinogen , but more likely they used substances secreted by the Colorado River toad Bufo alvarius. These contain bufotenin 5-MeO-DMT , a psychoactive compound that has been used in modern times as a recreational drug. Typically, the skin secretions are dried and then smoked. Exudations from the skin of the golden poison frog Phyllobates terribilis are traditionally used by native Colombians to poison the darts they use for hunting.

The tip of the projectile is rubbed over the back of the frog and the dart is launched from a blowgun. The combination of the two alkaloid toxins batrachotoxin and homobatrachotoxin is so powerful, one frog contains enough poison to kill an estimated 22, mice. These are less toxic and less abundant than the golden poison frog. They are impaled on pointed sticks and may be heated over a fire to maximise the quantity of poison that can be transferred to the dart.

Frogs feature prominently in folklore , fairy tales , and popular culture. They tend to be portrayed as benign, ugly, and clumsy, but with hidden talents. Examples include Michigan J. Frog, that will only dance and sing for the demolition worker who opens his time capsule, but will not perform in public. The Moche people of ancient Peru worshipped animals, and often depicted frogs in their art.

Some believed when one of these frogs died, it would turn into a golden talisman known as a huaca. Today, despite being extinct in the wild, Panamanian golden frogs remain an important cultural symbol and are illustrated on decorative cloth molas made by the Kuna people. They also appear as part of the inlaid design on a new overpass in Panama City , on T-shirts, and even on lottery tickets. From Wikipedia, the free encyclopedia. Order of amphibians. This article is about the group of amphibians. For other uses, see Frog disambiguation. See also: Sexual selection in amphibians. Play media. See also: Sexual selection in frogs. Larva of the common frog Rana temporaria a day before metamorphosis. Metamorphosis stage with deforming jaws, large eyes, and remains of gill pouch.

See also: Decline in amphibian populations. Main article: Frog legs. See also: Animal testing on frogs. See also: Frogs in captivity. Main article: Frogs in culture. Retrieved Tree of Life Web Project. Airlife Publishing. ISBN University of California, Berkeley. Paris: Hachette. OCLC Retrieved December 9, Oxford English Dictionary Online ed.

Oxford University Press. Subscription or participating institution membership required. Herpetology: Third Edition. Benjamin Cummings. Amphibian Species of the World: an Online Reference. Version 6. American Museum of Natural History. Retrieved 7 April Biology of Amphibians , p. Tree of Life web project. Herpetological Monographs. JSTOR Bulletin of the American Museum of Natural History. CiteSeerX Dissertation for thesis.

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