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| The sea star, which is sometimes called the starfish, can be in size from less than ½ in. to over 3 ft in diameter. They are mostly dull shades of yellow or orange, but there are many that are brightly colored, too. There are about 2,000 different kinds all over the world, mostly in shallow water along rocky coasts. http://www.discovery.com The body of most species consists
of a central disk from which radiate a number of tapering arms—usually five,
but up to 25 in some species. Some sea stars are pentagonal, the points of the
disk not extending into arms. Each arm contains an extension of the body cavity
and body organs. A network of calcareous plates located beneath the skin forms
an external skeleton; the plates are joined by connective tissue and muscle,
giving the apparently rigid sea star considerable flexibility. Calcareous
spines, some of them movable, project from the skin. |
