There are 6184 species of amphibians today. The West African goliath frog, which is 30 cm long and weighs 3.3 kilograms, is the largest anuran and the smallest is the Brazilian brachycephalid tree frog, which reaches a length of only 9.8 mm. Frogs and toads show the greatest diversity in tropics while salamanders inhabit the northern hemisphere in cool, moist forests.
Frogs and toads are tail-less amphibians that have large, well-developed eyes, short, thick bodies and four legs. Frogs have long, powerful hind legs that are well adapted for leaping and swimming. Tree frogs have suction pads on their fingers and toes for climbing. Toads have shorter legs than frogs adapted for hopping or walking instead of leaping. The skin of toads has a dry, warty appearance.
Salamanders have tail, short bodies, four almost equal legs and moist skin. They are often brightly colored and have great powers of regeneration. Most salamanders are about 4 to 6 inches long but the Chinese giant salamander (Megalobatrachus) grows to 5 feet in length. A tiny species in Mexico measures only about 1 inch.
Caecilians look like worms or snakes with a short pointed tail. They are well adapted for burrowing in moist sand. The long, slender body has numerous grooves. The eyes are small and covered by skin. There is a tentacle that is a tactile organ. Caecilian species range in length from about 10 cm to nearly 1.5 meters.
The Beddome’s Caecilian, Ichthyophis beddomei, found in Kerala (India) is known to have 25 to 38 eggs in an egg clutch. Egg size ranges from 6 mm at the time of laying to 12 mm at the time of hatching. Eggs generally hatch in 60 to 90 days. A newly hatched larva possesses 3 pairs of external pinnate gills.
Boulengerula taitanus is a oviparous caecilian found in Kenya, the skin of which is transformed in brooding females to provide a rich supply of nutrients for the developing larvae, which are equipped with a specialized dentition, which they use to peel and eat the outer layer of their mother’s modified skin.
Dermophis mexicanus is a Central American salamander, whose mother produces a nutritious secretion from the oviductal glands. Foetal caecilians move around within the oviduct and have specialized dentition with which they scrape the oviduct skin in order to stimulate and ingest the mother’s nutritive secretion.
Gegeneophis seshachari resembles other viviparous caecilians in having foetuses that ingest thickened oviduct lining using specialized deciduous teeth. G. seshachari is the smallest known viviparous caecilian.
Hynobius retardatus is a chocolate brown salamander found in Northern Japanese island of Hokkaido. Each female lays eggs in an egg sac which is attached on the robust branches that run horizontally touching the water surface.
The Paghman mountain salamander (Paradactylodon mustersi) is entirely water-dwelling and is restricted to three tributaries of the Paghman stream in Afghanistan. This species seems to prefer cold, fast-flowing water below 14°C.
The Gorgan mountain salamander (Paradactylodon gorganensis) is restricted to a single cave and stream in the mountains of northern Iran. It lives almost entirely in water, feeding on invertebrates and breeding in a long, narrow pool within the Shir-Abad cave.
Andrias occurs in central China and Japan, whereas Cryptobranchus lives in eastern North America. Males prepare nests below large, submerged stones or logs. Females lay long, paired strings of several hundred eggs which are fertilized by male.
FROGS & TOADS
The Australian Pouched Frog (Assa darlingtoni) has pouches along the side of body of males in which the tadpoles reside until metamorphosis.
The strawberry poison-dart frog (Oophaga pumilio) is found in Central America. Strawberry Poison Dart Frogs avoid laying eggs in ponds and streams. Instead, the eggs develop on land until the tadpoles are ready to hatch. Then the mother carries the tadpoles on her back to water-filled epiphytic plants on the trees.
Gastric-brooding frogs, Rheobatrachus silus and Rheobatrachus vitellinus are the only frogs which carry about 20 young in the stomach, during which they do not feed. The female swallows the eggs after the male fertilizes them.
Mountain Chicken Frog, Leptodactylus fallax is highly endangered and limited to Dominica, St. Kits, Martinique and a few neighbouring islands, lays eggs in foam nests underground, and the tadpoles develop without ever seeing water.
Rhinoderma darwinii or Darwin’s Frog’s males, brood their developing young in their vocal sacs until they metamorphose.
Moustache frog,Vibrissaphora ailaonica undergoes quite a transformation just before the breeding season. The males begin growing long hair-like skin extensions from one end of their mouth to the other. They also choose large boulders near a stream and build nest underneath it, where they guard eggs of any female who come and mate with them.
Midwife toads, Alytis cisternasii and A. obstetricans found in Europe attach the fertilized eggs to their hind legs. The males wrap them around his ankles. Sometimes they mate up to four times, carrying up to 200 eggs upon their bodies.