A caecilian is a type of amphibian that lacks any limbs, and is therefore snake-like in appearance. These animals are usually found in the tropical areas of South Asia, South America, and Africa. There are nine genera of caecilians, containing several dozen species. The typical caecilian has glossy skin and is covered with rings called annuli. A caecilian may be orange, grey, brown, black or yellow, although some species are very bright in color.
Scientists know little about the evolutionary history of these animals. The earliest fossils discovered come from the Jurassic period, and no caecilian fossils were found until about 1972. Fossil records indicate that early caecilians probably had small, underdeveloped limbs, and much larger eyes. Scientists believe that caecilians may be more closely related to egg-laying reptiles than other types of amphibians, such as frogs.
These animals typically live underground, burrowing through soft, loose soil. They often have very miniscule eyes, or no eyes at all. Small antennae found between their eyes and nasal openings allow them to navigate and locate prey. They typically feed on termites, grubs, small reptiles, beetle pupae, mollusks, and each other. Toxic skin excretions help to protect them from predation.
Without legs, the typical caecilian relies on its strong muscles to propel it through the loose soil in which it typically makes its home. These animals generally have powerful jaws and many sharp teeth. The animal's head is almost indistinguishable from its rear end. Some species are purely aquatic, and all species are normally comfortable in the water and able to swim very well. Most species have lungs, but they can also absorb oxygen through their skin.
Some types of caecilian reproduce by laying eggs, while others give birth to live young or to young in a larval stage of development. When a female caecilian is of an egg-laying species, she usually deposits her eggs in small burrows near the waterside. The young typically hatch in a larval stage of development. They live in the water, feeding on plankton as they develop. As adults, they generally emerge from the water to live the rest of the their lives in underground tunnels.
The size of a caecilian may vary widely according to its species. Some species are about the size of earthworms. Larger species may grow to an adult size of 59 inches (1.5 meters). Depending on the species, a caecilian may live for five to 20 years.