Brittle Star

(Subclass Ophiuroidea)

Brittle stars are echinoderms, which means that they're related to starfish (or more accurately, sea stars.) They have pentamerous radial symmetry, which means that they have 5 arms arranged around a central disk. They are appropriately named, because these arms end to break off, thus "brittle" stars. Luckily, they are able to regenerate them. Unlike their somewhat passive cousins the sea stars, brittle stars are relatively fast, and their thin, whip-like arms tend to writhe independently of each other when the animal is disturbed. When I held one in Inverebrate Zoology it reminded me of something from a cheesy horror film. Some, such as the one above, have spines that project off of the arms. They tend to hide under rocks or among seaweeds, and eat small particles of detritus or small organisms like worms. Closely related to brittle stars, basket stars (which have long tangled arms, hence the name) are also Ophiuroids.