Marine Environment - Brittle Stars |
Brittle Stars
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General Brittle stars form part of the group called echinoderms, which means "spiny skinned", and are in a class called Ophiuroidea, which means "snake like". The skins of these creatures are filled with hard plates or spines and most have the body divided into 5 radial parts extending from a central disc. Members of this group can regrow lost body parts, with some being able to grow a fragment into a new individual. Brittle stars can be either male or female. The arms are either smoothe, spiny or branching but lack a groove like the sea stars. Brittle stars have only one set of internal organs, situated in the central disc. There is a toothed mouth and water pressure pore on the underside of the disc, but no anus. The flexible arms are made of tiny rings held together with muscle-like tissue. The tube feet of a brittle star lack adhesive suckers. Some produce slimy mucus which traps tiny organisms, so the arms can be used to filter plankton from the current. A brittle star may shovel sand or mud into its mouth, which is armed with tiny teeth. Animal and vegetable content are digested. Usually feed on detritus or prey on worms, crustaceans and bivalves. To escape attacks the brittle star may shed their arms, whick then can regrow. Movement is achieved by using its arms in a rowing like fashion. Compared to the sea star the brittle star is a fast moving. Usually found below the low tide water mark, on the bottom under rocks and corals. They tend to avoid direct sunlight and range between 10-75 cm in diameter. Specialised forms of brittle stars are Basket stars, which have multi-branched arms, and serpent stars, which often coil around the branches of gorgonians.
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