At present the Class Amphibia is represented by three Orders: the Apoda, which encompasses the worm-like CAECILIANS, the Caudata or ‘tailed amphibians’ that are represented by NEWTS & SALAMANDERS, and the Salientia which includes FROGS & TOADS.
On hatching, a larva emerges from the egg. In the frogs and toads, this is the tadpole. Most amphibian larvae usually start off with external gills but tadpoles generally have internal gills. The next major changes in the tadpole are usually seen when the adult stage is reached. Tadpole demonstrates the most striking changes with the appearance of limbs and disappearance of the tail. The major changes in the tailed and legless at metamorphosis is usually the disappearance of the external gills. Before metamorphosis, the lungs develop and are functional by the time the gills begin to disappear.
Of the three living orders of amphibia, only two have been known to produce any vocalization - the frogs and toads, and tailed amphibians. All the amphibian calls one hears on the Indian subcontinent come from frogs and toads.Although calls to attract mates (mating calls) are the commonest uses of voice in amphibians, there are five other conditions which may give rise to sounds. These sounds are called release calls, warning sounds, rain calls, screams, and territoriality calls.
The length of life in the amphibia has been recorded to vary from as short as two years in the spadefoot toads to as long as fifty years from some salamanders; the larger animals live longer than the smaller ones.
References: Encyclopedia of Indian Natural History (BNHS), IUCN Red List, Envis Newsletter (Oct-Dec 2001)
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