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excentricat1 · 23 days ago

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Round 3 - Lissamphibia - Gymnophiona

(Sources - 1, 2, 3, 4)

Order: Gymnophiona

Common Name: “caecilians”

Families: 10 - Caeciliidae (“common caecilians”), Chikilidae (“Indian caecilians”), Dermophiidae (“Neotropical caecilians”), Herpelidae (“African caecilians”), Ichthyophiidae (“Asiatic tailed caecilians”), Grandisoniidae (“Indo-African caecilians”), Rhinatrematidae (“Neotropical tailed caecilians”), Scolecomorphidae (“tropical caecilians”), Siphonopidae (also “common caecilians”), and Typhlonectidae (“aquatic caecilians”)

Anatomy: long, limbless, cylindrical bodies; bullet-shaped and strongly built skulls; small or sometimes nonexistent eyes; small chemosensory tentacles in front of the eyes; slimy skin that bears ringlike markings or grooves and may contain scales

Diet: small subterranean animals, such as earthworms.

Habitat/Range: tropics of South and Central America, Africa, and southern Asia; mostly live hidden in soil or in streambeds

Evolved in: Late Triassic

Propaganda under the cut:

Caecilians mostly live hidden underground or in streambeds, and thus they are the least familiar and least studied lissamphibians.

Like other lissamphibians, caecilians mainly use their skin and mouths for oxygen absorption, and one species, Atretochoana eiselti, lacks lungs entirely.

The Ringed Caecilian (Siphonops annulatus) has dental glands that may be homologous to the venom glands of some snakes and lizards, but the function of these glands is unknown. Glands on the tail region are packed with noxious chemicals, similar to the poison glands found in toads and newts.

About 25% of caecilian species are oviparous (egg-laying). Eggs are laid in terrestrial nests rather than in water and are guarded by the female. For some species, the young caecilians are already metamorphosed when they hatch, while others hatch as larvae. Larvae are not fully aquatic, but spend the daytime in the soil near the water. However, most caecilians are viviparous, giving birth to already-developed offspring. The foetus is fed inside the female with cells lining the oviduct, which they eat with special scraping teeth. Some larvae, such as those of Typhlonectes, are born with enormous external gills which are shed almost immediately after birth.

Rare for lissamphibians, all caecilians care for their young (image 3), even “nursing” them with a milk similar to mammalian milk. Some species even feed their young by growing a special outer layer of skin, high in fat and other nutrients, which the young peel off with modified teeth. As it does in nursing mammals, this also helps transfer microbes from the mother to her young, promoting a healthy microbiome. Researchers have observed hatchlings emitting high-pitched clicking sounds as they approached their mothers for milk, a behavior unique among amphibians.

In the folklore of certain regions of India, caecilians are feared and reviled, based on the (false) belief that they are fatally venomous. Caecilians in the Eastern Himalayas are colloquially known as "back ache snakes", while in the Western Ghats, Ichthyophis tricolor is considered to be more toxic than a cobra. Despite deep cultural respect for the cobra and other dangerous animals, the caecilian is killed on sight with salt and kerosene. These myths have complicated conservation initiatives for Indian caecilians.

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excentricat1 · 24 days ago

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Round 3 - Lissamphibia - Anura

(Sources - 1, 2, 3, 4)

Order: Anura

Common Name: “frogs”

Families: 54 - Ascaphidae (“tailed frogs”), Bombinatoridae (“flat-headed frogs” and “firebelly toads”), Alytidae (“painted frogs”), Leiopelmatidae (“New Zealand primitive frogs”), Megophryidae (“goose frogs”), Pelobatidae (“European spadefoot toads”), Pelodytidae (“parsley frogs”), Pipidae (Pipid frogs), Rhinophrynidae (“Mexican burrowing toads”), Scaphiopodidae (“American spadefoot toads”), Heleophrynidae (“ghost frogs”), Allophrynidae (“Tukeit Hill frogs”), Alsodidae, Batrachylidae, Bufonidae (“true toads”), Brachycephalidae (“saddleback toads”), Caligophrynidae, Ceuthomantidae (“emerald-barred frogs”), Craugastoridae (“fleshbelly frogs”), Eleutherodactylidae (“rain frogs”), Neblinaphrynidae, Strabomantidae (“cloud forest landfrogs”), Centrolenidae (“glass frogs”), Ceratophryidae (“common horned frogs”), Cycloramphidae, Dendrobatidae (“poison dart frogs”), Aromobatidae (“cryptic forest frogs”), Hemiphractidae, Hylidae (“tree frogs” and kin), Hylodidae (“giant Neotropical torrent frogs”), Leptodactylidae (“southern frogs”), Odontophrynidae, Rhinodermatidae (“Darwin’s frogs”), Telmatobiidae, Calyptocephalellidae, Limnodynastidae (“Australian ground frogs”), Myobatrachidae (“Australian water frogs”), Nasikabatrachidae (“purple frogs”), Sooglossidae (“Seychelles frogs”), Arthroleptidae (“African tree frogs”), Ceratobatrachidae, Conrauidae (“slippery frogs”), Dicroglossidae (“fork-tongued frogs”), Hyperoliidae (“sedge frogs”), Microhylidae (“narrow-mouthed frogs”), Micrixalidae (“dancing frogs”), Nyctibatrachidae (“robust frogs”), Petropedetidae (“African torrent frogs”), Phrynobatrachidae (“puddle frogs”), Ptychadenidae (“grassland frogs”), Pyxicephalidae, Ranidae (“true frogs”), Ranixalidae (“leaping frogs”), and Rhacophoridae (“shrub frogs”)

Anatomy: metamorphosis from tailed, gilled, aquatic “tadpole” larvae; adults have no tail; longer hindlimbs than forelimbs; elongated ankle bones; webbed toes; large eyes; adhesive tongues; no external ears, eardrums are either exposed or covered by a skin membrane; smooth or “warty” skin which has a respiratory function and most can absorb water; most species can exude distasteful and toxic substances, as well as secretions to keep the skin moist

Diet: invertebrates and small vertebrates

Habitat/Range: every continent except Antarctica, with greatest diversity in tropical areas; most frogs require humid or damp environments, though some are adapted to survive in arid or cold habitats

Evolved in: Early Jurassic

Propaganda under the cut:

Frog tongues are covered in a two-phase viscoelastic fluid. When exposed to pressure, like when the tongue is wrapping around prey, their saliva becomes runny and covers the prey's body. As the pressure drops, it returns to a thick and elastic state, which gives the tongue an extra grip. Their tongue can be shot out and retracted at great speed, but is not as long as cartoons make it out to be, and is generally about 1/3 the length of the frog’s body, depending on species. Some frogs have no tongue and just stuff food into their mouths with their hands.

Frog eyes are situated on the very top of the animals’ head, and provide binocular vision over a field of 100° to the front and a total visual field of almost 360°. 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 clearly it is seen. They can also see in colour, even in very low light.

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 (1.6 km) away. Additionally, some species have been found to use man-made structures such as drain pipes for artificial amplification of their call. The main function of calling is for male frogs to attract mates. Males may call individually or there may be a chorus of sound where numerous males have converged on breeding sites. Female frogs prefer males that produce sounds of greater intensity and lower frequency, attributes that stand out in a crowd. There are other calls given by unreceptive frogs who have been mounted, calls before a rain, territorial calls meant to drive away other males, and distress calls meant to surprise or disorient an attacker.

Frogs do most of their breathing through their skin, and are able to survive without lungs. The fully aquatic Bornean Flat-headed Frog (Barbourula kalimantanensis) is the first frog known to lack lungs entirely.

Only members of the family Bufonidae are considered "true toads", but “toad” is also generally used for frog species that are terrestrial with dry, warty skin. There are numerous exceptions to this rule. The European Fire-bellied Toad (Bombina bombina) has a slightly warty skin and prefers a watery habitat, whereas the Panamanian Golden Frog (Atelopus zeteki) is in the toad family Bufonidae and has smooth skin.

The Panamanian Golden Frog is critically endangered, and most likely extinct in the wild since 2007. It was filmed for the last time in the wild in 2006 by the BBC Natural History Unit for the series Life in Cold Blood by David Attenborough, with the location of filming kept secret to protect the toads from potential poachers. The two distinct populations of the toad can now only be found in captivity, under a dedicated captive breeding program. They were nearly wiped out mainly due to the introduction of chytridiomycosis. As nothing seems to be able to control or stop the spread of chytrid, the current hope is to breed frogs that are more resilient and resistant to the fungal disease.

Chytridiomycosis is an infectious disease in amphibians, caused by the chytrid fungi Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans. It has been linked to dramatic population declines and extinctions of amphibian species in western North America, Central America, South America, eastern Australia, Tanzania, Dominica, and Montserrat. Much of the New World is at risk of the disease arriving within the coming years. It is thought to have been introduced or at least spread by imported African Clawed Frogs (Xenopus laevis) which are immune to the disease, and were once used for human pregnancy testing and thus traded in large amounts. The fungus affects the skin of amphibians, which is disastrous for animals which take in water and oxygen through their skin. As the fungus can multiply from one single microscopic spore in a water source, no effective measure is known for control of the disease in wild populations.

The colour of a frog's skin is used for thermoregulation. In cool damp conditions, the colour will be darker than on a hot dry day. The Grey Foam-nest Tree Frog (Chiromantis xerampelina) is even able to turn white to minimise the chance of overheating.

The male Hairy Frog (Trichobatrachus robustus) has dermal papillae projecting from its lower back and thighs, giving it a bristly, hairy appearance. These contain blood vessels and are thought to increase the area of the skin available for respiration. This is particularly useful for the males, as they stay with and guard their eggs until the tadpoles emerge.

Some poison frogs carry their young to place in individual water-filled bromeliads, periodically returning to each individual tadpole to deposit unfertilized eggs for them to eat. Male Darwin Frogs (Rhinoderma darwinii) carry their young in their vocal sac, keeping them safe from predators. Suriname Toads (Pipa pipa) incubate their eggs in pits on their back (if you have trypophobia you probably already know about this, but if not, don’t look it up).

The Pacific Tree Frog (Pseudacris regilla) is the only frog known to produce the onomatopoeic "ribbit" often heard in films.

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. Some frogs such as the Wood Frog (Lithobates sylvaticus), Moor Frog (Rana arvalis), and Spring Peeper (Pseudacris crucifer) 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.

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 to ten months of the year. It burrows underground and curls up inside a protective cocoon formed by its shed skin.

The Striped Rocket Frog (Litoria nasuta) can leap over two metres (6.5 feet), a distance that is more than fifty times its body length of 55 mm (2.25 in).

The tiny Northern Cricket Frog (Acris crepitans) can "skip" across the surface of a pond with a series of short rapid jumps.

The smallest amphibian, and vertebrate, in the world is the Brazilian Flea Toad (Brachycephalus pulex) (image 2), at 8–8.4 mm long from snout to vent. Brachycephalus species (called “Saddleback Toads”) are so tiny that their vestibular systems are too small for dependable locomotion, and their balance is lost mid-air when jumping.

The Red-legged Running Frog (Kassina maculata) has short, slim hind limbs unsuitable for 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 remains similar at slow, medium, and fast speeds.

The Purple Frog (Nasikabatrachus sahyadrensis) from southern India feeds on termites and spends almost its whole life underground, emerging only briefly during the monsoon to mate and breed in temporary pools.

Tree frogs are very acrobatic and can catch insects while hanging by one toe from a twig or clutching onto the blade of a reed.

Some frogs in tropical rainforests are specially adapted for gliding from tree to tree or parachuting to the forest floor. One example 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, though it is unable to take powered flight. It can alter its direction of travel and navigate distances of up to 15 m (50 ft) between trees.

Almost all frogs are poisonous, but their poisons vary. The chemicals involved may be irritants, hallucinogens, convulsants, nerve poisons or vasoconstrictors. Some frogs obtain poisons from the ants and other arthropods they eat, while others can synthesize the chemicals themselves. Some non-poisonous frogs mimic the coloration of poisonous species.

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. Two other species, the Kokoe Poison Dart Frog (Phyllobates aurotaenia) and the Black-legged Dart Frog (Phyllobates bicolor) are also used for this purpose, though they are less toxic and less abundant than the Golden Poison Frog.

The alkaloid epibatidine, a painkiller 200 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. Dart poisons are under active investigation for their potential as therapeutic drugs.

Illicit drug use by licking the skin of the Colorado River Toad (Incilius alvarius) has been reported in the media, but this may be an urban myth. Typically, the skin secretions are dried and then smoked.

The Han people of China depict a legendary bullfrog, Jin Chan, sitting on a pile of traditional Chinese cash, with a coin in its mouth. According to feng shui beliefs, a Jin Chan charm helps attract and protect wealth, and guards against bad luck. The ancient Egyptians depicted the god Heqet, protector of newborns, with the head of a frog. For the Mayans, frogs represented water, crops, fertility and birth and were associated with the god Chaac.

The Mountain Chicken (Leptodactylus fallax), a frog so named because of its taste, is now critically endangered in part due to human consumption, as well as habitat loss and chytridiomycosis.

Frog populations have declined dramatically since the 1950s. More than 1/3 of frog species are considered to be threatened with extinction, and more than 120 species have become extinct since the 1980s. As all frogs depend on water to survive, habitat loss and pollutants are a significant cause of frog population decline. Other causes are heavy traffic in their environments, increased UVB radiation, the introduction of invasive species, and infectious diseases, such as ranovirus and the aforementioned chytridiomycosis. Environmental scientists believe amphibians, including frogs, are good biological indicators of broader ecosystem health because of their intermediate positions in food chains. The frogs are the “canaries in the coal mine”, and their decline is a signal of possible ecosystem collapse.

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