Ophiomusa

Ophiomusa is a genus of echinoderms, which includes sea urchins, sand dollars and sea cucumbers, belonging to the family Ophiolepididae. Ophiurida are similar to starfish; they both have a central disc and five arms sprouting from the disc. One of the main distinguishing factors of an Ophiuroid is its arms; the arms of an Ophiurida are longer, thinner, and distinctly separated in comparison to those of a sea star.

== Description == Ophiuroids, also known as brittle stars, are relatively small. Brittle stars do not have a brain or eyes, but they do have a stomach, sex organs, and a mouth with five jaws. They have five long, thin, spiny arms made of calcium carbonate plates connected by a central disc; the size of their disk ranges from 6-12mm disc diameter (d.d.), and their arms range from sizes greater than 4 times d.d. in length. The first dorsal arm plates are in the shape of a trapezoid, the next dorsal arm changes to a triangular form and are each separated from each other. Their arms contribute to the star's “snake-like” movement across the bottom sediments as well as its feeding mechanisms. The mouth of an Ophiuroid is located on the oral surface which is facing down but is held off the sea floor. An interesting fact about Ophiuroids is that, like regular sea stars, they have the ability to regenerate a severed arm, they even possess the ability to cut off their own arm if necessary. This is referred to as autotomy (self-cut) which is how it got its name, brittle star. The spiny arms of the brittle star allow the animal to roam without losing grip from the substratum.