are the common brittle star invertebrates
Most brittle stars are under 1 inch (2.5 cm) in diameter. They have a hard endoskeleton and vary in color. They do not have a brain; they have a simple ring of nerve cells that moves information around the body. Tube feet located along the arms sense light and smells. Brittle Star. The most common brittle star is the long-armed brittle star (Amphipholis squamata), a gray-blue, luminescent (glowing) species. Anatomy: Most brittle stars have five (or a multiple of five) long, thin, spiny arms that radiate from a flat central disk; the arms do not touch each other at their bases. Many of the arms are forked. If a brittle star's arm is cut off, it will regenerate (regrow). The Ophiuroidea contain two large clades, Ophiurida (brittle stars) and Euryalida (basket stars). Many of the ophiuroids are rarely encountered in the relatively shallow depths normally visited by humans, but they are a diverse group. Brittle stars are a moderately popular invertebrate in fishkeeping. They can easily thrive in marine tanks; in fact, the micro brittle star is a common hitchhiker that will propagate and become common in almost any saltwater tank, if one happens to come along on some live rock. Cool Facts. Brittle stars occur in incredible numbers on the sandy seafloor. In kelp forests near La Jolla in southern California, millions of them may carpet the seafloor in layers up to an inch thick! Brittle stars live in a wide range of water depths—from the shoreline down to 6,755 feet (2,059 m). Natural History. Brittle stars live on spiny sponges and other sessile animals in massive fields on the muddy seafloor, as well as by themselves or in abundance directly on the seafloor. Brittle stars use their arms for locomotion. They do not, like sea stars, depend on tube feet, which are mere sensory tentacles without suction. Brittle stars move fairly rapidly by wriggling their arms which are highly flexible and enable the animals to make either snake-like or rowing movements. However, they tend to attach themselves to the sea floor or to sponges or cnidarians, such as coral. Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. Diet: Brittle stars are mainly detrivores (detritus-eaters); they eat decaying matter and plankton. Some brittle stars can also kill small animals. They push their stomach out through their mouth (which is located on the underside of the disk of the brittle stars) and digest the prey (there is no anus). Natural History. Brittle stars are sea star cousins that bury themselves for protection, leaving an arm or two free to catch bits of food. Sometimes this attracts a hungry fish but fortunately, a star can't be tugged out by the arm. The arm snaps off, and a new one grows from the stump.
Yes