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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 Amphibia, Anura, Urodela
(or Gymnophiona), an order of amphibians, including one family, the Caecilidae, so-called because of their similarity to large rain worms. About 20 genera (70 species) are known. They are distributed in the tropical countries of Africa, Asia, and America. Apoda live in the ground, except for specimens of the South American genus Typhlonectes, which live in the water. Apoda are adapted to a digging mode of life. The wormlike body, lacking external extremities, is divided by transverse grooves into numerous rings. The eyes are undeveloped and hidden under the skin. Apoda lack a tympanum. The sense of smell is well developed. They have a tactile tentacle, which protrudes from a deep pit placed behind or beneath the nostrils. The number of vertebrae can reach 300. The internal organs are greatly extended. The cloaca of males can protrude, forming a copulatory organ. Fertilization is internal. The majority of members of this order lay a small number of yolk-rich eggs in earthen burrows. In some species, larvae emerge to finish their metamorphosis in the water; in others, development is finished in the egg. Some varieties are live-bearers. The Ceylonese fishsnake (Ichthyophis glutinosus) is found in Southeast Asia; it is an amphibian up to 38 cm long, bluish black in color, with wide bright yellow stripes along the sides of the body. It feeds on rain worms and other small soil animals, among which are blind snakes. The female lays 10–15 eggs about one cm in diameter in burrows near the water, coils herself about the eggs, and stays in that position until the larvae emerge. The larvae, up to 4 cm long, leave the egg membranes and move to the water, where they complete their development. The genus of Caecilia, distributed in tropical South America, includes much larger specimens, up to 1 m long.
REFERENCESTerent’ev, P. V. Gerpetologiia. Moscow, 1961.
Nieden, F. Gymnophiona. Berlin, 1913. (Das Tierreich, fasc. 37.)
Taylor, E. H. The Caecilians of the World. Lawrence, Kan., 1968.
N. V. SHIBANOV