Caecilians are a generally unknown group represented by 163 species of elongate snake-like animals living in tropical rainforests in South America, Africa and South East Asia.
Caecilians are either aquatic or specialised for burrowing being found in moist loose soil in tropical forest and plantations, often near streams. They use their heads to dig or poke in mud for food. Their eyes are reduced and covered by skin, but can apparently sense light. Caecilians have a unique sensory tentacle, that develops at metamorphosis, on the upper jaw behind each nostril which enhances their sense of smell. The lack of limbs and limb girdles are adaptations for an undulating form of locomotion. In water, they can swim by undulating movements of the body. In the restricted confines of a burrow, they advance by keeping parts of the body in contact with the ground while extending other parts forwards.
The reproductive strategies of caecilians are as diverse as those of members of the other two orders of amphibians. Some species lay eggs in burrows near water. The eggs hatch into gilled larvae that wriggle into water; the young become terrestrial after metamorphosis. Other species may lay eggs underground and the young hatch out as small miniature adults. About half of the known species are viviparous: the young develop through metamorphosis in the female’s oviducts being nourished first by the yolk sac and then by maternal secretions.
Siphonops annulatus, a member of the Family Caeciliidae, occurs in tropical transandean South America.