Monday, April 23, 2012

Interesting Animals: Caecilians

One of the caecilian species in the Order Gymnophiona
Caecilians look a great deal like snakes or large worms, but they are in fact legless amphibians. They are placed in their own Order Gymnophiona, a decision which is supported by genetic analysis. These creatures are adapted for a burrowing lifestyle, though there are some species that are aquatic. They live in moist areas that are fairly close to the equator as, like all amphibians, these creatures need a stay moist. They are blind, with severely reduced eyes, and have no ear opening, so thus probably can't hear. They mostly use sensory protrusions near their eyes to find their way around as well as locate prey. They are carnivores, with quite sharp teeth that they use to capture prey. They eat invertebrates such as beetles or worms, and also will eat snakes and amphibians, including caecilians. They aren't often eaten themselves as they are, in fact, toxic.

One rather remarkable characteristic that these animals exhibit is that mothers feed their young. This feeding is very unusual in the animal kingdom, though, in that mothers develop tissue inside of the oviduct for this purpose. Early on, eggs develop as normal, with the offspring feeding on the yolk. However, after this food supply is gone the offspring break out and then latch onto their mother's oviduct tissue. The tissue releases a milk-like substance specifically produced for feeding the young, but the babies also take chunks out of the tissue as they feed. Other species have an even more bizarre method in which the young scrape the skin off of their mother's body. Caecilians are also unusual among amphibians in that fertilization is internal.

Below is a video depicting these unusual creatures and some of their habits, narrated by the ever-wonderful David Attenborough. Discussion of Caecilians begins at 0:24.

Sources are the San Diego Zoo, Animal Diversity Web, and Vertebrate Life. Image is from Wikimedia Commons under a Creative Commons license. Video is from YouTube.

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