When I think of amphibians, the first things that pop into my head are frogs and toads. After that, I remember that salamanders and newts are also amphibians. What doesn’t come to mind is the caecilians. So when I was browsing through a website the other day and saw ‘frogs, salamanders and caecilians’ listed under amphibians, I just had to find out what caecilians are.
Caecilians belong to an order of legless amphibians, Gymnophiona. They are not usually seen by people, as most species live underground. If you do want to see one, try digging up soil in wet, tropical regions of Central and South America, costal Africa, and Southeast Asia. There are almost 200 species of caecilians in the world, so it’s a little strange that they are so poorly known.
As I mentioned, caecilians are legless, so most of them either look like snakes or worms. Some species can get quite large, reaching lengths of over a meter. Most species have dark or boring coloured skin, but some caecilians can be quite colourful. Their skin is covered in lot of folds, called annuli, that really emphasize the worm-like appearance of caecilians. Since they live underground, caecilians tend to not use sight very much. So most species have very poorly developed eyes, which can only be used to detect light and dark. They also have a pointed skull that helps the caecilian burrow underground.
Caecilians feed on insects and small vertebrates, such as snakes, frogs and lizards. They have tiny, needle-like teeth in their mouths, which are used to catch and grip prey, not to chew, as caecilians swallow their prey whole. Organs in the caecilians’ ears help the animals detect prey, by sensing vibrations in the ground. They also have tentacles between their eyes and nose that help caecilians find their way around. Their skin secretes toxic compounds to help protect caecilians from predators.
Reproduction in caecilians occurs in one of two ways: either eggs are laid in water and later move underground as they develop, or the young are simply born live from the mother. Some egg laying species provide care for their young after they hatch, in a bit of a creepy way. The mother grows a thick layer of skin that is rich in fat and nutrients, and her children eat it. A new skin is grown every three days until the young can survive on their own. I’m sorry, but that just seems like taking parenting a bit too far. Another weird thing about caecilians is that they all use internal fertilization, something no other amphibians do.
Not a lot of people know about caecilians, and not much is known about them. It’s a shame, because from what we do know, it seems like caecilians are a really neat group of animals.
Cover image by Franco Andreone – see authorization, CC BY-SA 2.5, via Wikimedia Commons