BIO 1106 Study Guide - Midterm Guide: Water Vascular System, Madreporite, Ambulacral
28 Nov 2016
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Characterized by their spiny skin, have an internal skeleton of calcareous plates called ossicles that usually have spines protruding through a thin layer of skin. Also characterized by penta-radial symmetry (in adults) and a unique water vascular system: larva have bilateral symmetry. 5 classes are characterized by the arrangement of their ossicles. Class asteroidea ossicles arranged loosely under the skin, spines are small and blunt, arms are continuous with a central disk. Asterias common sea star: slide of sea star larva (shows bilateral symmetry, slide of pedicellariae (pincerlike structures on sea star spines- fig. Class ophiruoidea (brittle stars) arms clearly separated from the central disk, reduced tube feed are not used for locomotion. Class crinoidea (sea lilies and feather stars) oral surface (mouth and anus) usually faces up, ossicles are well-developed and give a jointed appearance, highly branched and feathery arms: no actual specimen, just a picture.
