A little-known order of amphibians with a wormlike body and many unusual adaptations. In the currently accepted taxonomy, there are three orders within the class Amphibia: Anura (frogs), Caudata (salamanders), and Gymnophiona (caecilians).
Gymnophiona literally means "naked and gray". Older names for gymnophiona include apoda ("no feet"), ophiomorpha ("snake-shaped"), and ophidobatrachia ("snake amphibians"). They also go by the common name caecilians ("blind worms").
Caecilians are specialized to a fossorial, or burrowing, lifestyle. They have an earthworm-like segmented appearance and have no limbs. They also lack a tail, eardrums, and larynx. Only the right lung is large and functional, as in snakes. The skull is solid bone, with the cranial sutures ossified, and if eyes are present they are usually covered by skin and often by bone as well. Caecilians are the only amphibians known to have scales, which are embedded in their skin. They also make use of internal fertilization; unlike the other amphibian orders, males in Gymnophiona have a copulatory organ similar to a penis.
Caecilians are found in tropical areas in the Americas, Africa, and Asia. Most are burrowing species; a few, most notably Typhlonectes natans and T. compressicauda, have secondarily adapted to an aquatic lifestyle. These two were once somewhat common in the aquarium pet trade (they live in the same waters as many commonly-collected tropical fish) but lately are difficult to come by, and very expensive, due to a CITES ban.
References and further reading
Coborn, John. The Proper Care of Amphibians. T.F.H.Publications, Neptune City NJ 1992