Caecilians are amphibians that belong to the order Gymnophiona.
They live in tropical and subtropical habitats in Central and South America, India, Southeast Asia, Africa, Indonesia and the Seychelles Island, usually around swamps.
Caecilians have no legs, and some species have no tails. Although they are amphibians, they may be mistaken for worms, eels or snakes.
We know of at least 160 species of caecilian.
The smallest adult caecilians that we know of are about 4 ½ inches long, although some people claim to have seen adult caecilians as small as 2 inches long.
The largest caecilian that we know of is Thomson's caecilian (Caecilia thompsoni). It can grow up to 5 feet long and weigh more than 2 pounds.
Caecilians have smooth skins, which are usually a dull green or brown color. Some caecilians have brightly colored stripes.
Their skins have ring-shaped folds that are known as annuli. These annuli make caecilians look like earthworms.
Some species have a layer of scales underneath their outer layer of skin.
Most caecilians are burrowing animals. They dig in moist soil and in leaf litter.
They have many physical adaptations that make them suited to a burrowing lifestyle.
Caecilians have strong, hard skulls, with pointed snouts. Their skull bones are fused together. They use their skulls to push through mud and soil.
They have eyes that are covered with skin or set deep within their skulls. Caecilians are thought to be able to distinguish dark from light, but see little else.
Caecilians have no ear holes.
A caecilian has a pair of tentacles, which retract into grooves, between its eyes and nostrils.
Zoologists think that caecilians use their tentacles to sense chemicals in the air and to detect motion.
Because most caecilians live underground and are hard to find, we don't know much about them.
Some caecilians live in water. They have a small fin along the rear of their bodies. These caecilians resemble eels.
The rubber eel (Typhlonectes natans) is an aquatic caecilian from South America. It is sometimes called a Sicilian worm. Some people keep rubber eels as pets.
Caecilians are carnivores. Their diet includes termites, ants, beetles, worms, frogs, snakes, lizards and other caecilians. They find their prey underground or in leaf litter.
A caecilian has two rows of teeth in both its upper and lower jaws.
Like other amphibians, caecilians protect themselves from predators by secreting toxins from their skins.
All caecilians, like all amphibians, breathe through their skins. Skin-breathing is known as cutaneous respiration.
Caecilians also breathe through lungs.
A Caecilian has only one lung, not two.
Some species are lungless and breathe only through their skins when they are adults.
Caecilians reproduce by internal fertilization.
The male inserts a phallodeum, an organ that resembles a penis, inside the female's cloaca. A cloaca is an opening that is used for excretion and reproduction.
Some species of caecilian lay eggs in damp holes near water. Animals that lay eggs are oviparous.
Some caecilians give birth to live young (are viviparous).
Caecilian larvae have gills and short tails.
They are born with teeth and are carnivorous.
In some species, the mother has a fat layer of outer skin that is full of nutrients. The young use their teeth to peel off this layer of skin and eat it.
During metamorphosis, a caecilian loses its gills and may lose its tail.
It grows annuli, sensory tentacles and, usually, a lung.
Some caecilian species do not go through metamorphosis. When the young hatch or are born, they are already in their adult form.