Apoda

(vertebrate zoology) The caecilians, a small order of wormlike, legless animals in the class Amphibia.

The smallest order (sometimes called Gymnophiona) of the class Amphibia, known as the caecilians. These are wormlike, legless animals with indistinct or even hidden eyes. A series of annular grooves is usually present along the length of the body, heightening the resemblance to an earthworm. Most caecilians lead a burrowing existence, though members of one genus, Typhlonectes, are aquatic. Some species have the eyes hidden beneath the bones of the skull and probably are blind, but others at least are able to distinguish movement. A unique feature of the caecilians among modern Amphibia is the presence of scales buried in the skin of some species. There are more than 160 species of caecilians confined to tropical regions of both Eastern and Western hemispheres. Many species are less than 1 ft (0.3 m) in length, but three species of the genus Caecilia grow to over 3 ft (0.9 m). Some species lay eggs, while others bring forth their young alive. The embryos of the species that bear living young are nourished in the later part of their embryonic development by “uterine milk,” which is secreted by the mother. In some of the species that lay eggs there is an aquatic larval stage. Caecilians are carnivorous, but little is known of their food habits. Captive specimens have fed on earthworms, and in the natural state caecilians have eaten lizards. See also Amphibia; Anura; Urodela.