Brittle Star

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Brittle stars, or ophiuroids, are echinoderms, closely related to sea stars. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to 60 centimeters (2 feet) in length on the largest specimens. They are also known as serpent stars. There are some 1,500 species of brittle stars living today, and they are largely found in deep waters more than 500 metres (1,650 feet) down. The mouth is rimmed with five jaws, and serves as an anus (egestion) as well as ingestion. Behind the jaws is a short esophagus and a large, blind stomach cavity which occupies much of the dorsal half of the disk. Brittle stars can readily regenerate lost arms or arm segments unless all arms are lost. The disk is used to do this. Ophiuroids use this ability to escape predators, similar to how lizards deliberately shed (autotomize) the distal part of their tails to confuse pursuers. Moreover, the Amphiuridae can regenerate gut and gonad fragments lost along with the arms. 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 seafloor or to sponges or cnidarians, such as coral. Their movement has some similarities with animals with bilateral symmetry. Brittle stars generally sexually mature in 2 years, become full grown in 3 to 4 years, and live up to 5 years. [READ THE REST OF THIS ARTICLE]





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