|Hawaii Institute of Marine Biology|
Brittle stars are in the Echinoderm phylum. Like other echinoderms, they have a five-part body plan, with a distinct central disk and 5 arms. However, one of the more common brittle stars manages to add one more arm to make a total of six, so don't be surprised if they have gone beyond the norm. They vary radially in size and color. Many are tiny, like the 6 armed ones in our touch table which generally do not reach over 2 cm or so. But others found inter-tidally in Hawaii under rocks and such can have arm spans of 10 inches or more. They do not have a head or brain. Instead they have a simple ring of nerve cells that moves information around the body. Their small tube feet located along the arms can also sense light and smells, making them a key part of the brittle stars body plan.
Because these invertebrates are, well "brittle," their arms tend to break off. However, they have the ability to quickly regenerate their arms. If they are grabbed by a predator, they can drop an arm allowing for escape as a defense mechanism. Try to keep this brittle star tactic in mind and be very cautious when handling them. The arm may grow back, but they will be hindered in movement and feeding.
About Fish Online-Brittle Stars. N.p., 2008. Web. 2015.
"Brittle Star | Class of Echinoderms." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 29 July 2015.