These echinoderms are generally flattened body, slowly turning into radial "arms" (5-40), which are called rays. The shape and structural features of the rays are very diverse: from the broad and short, giving the animal a pentagonal shape to long and thin, resembling tentacles. In contrast to the lily, the mouth and ambulacral grooves stars located on the bottom, facing the substrate surface of the body.
In cases where the stars have the anus, it is like madreporite ambulacral system, is located on the right (dorsal) surface of the body.
All Stars - mobile organisms moving along the substrate with the ambulacral feet, located in the ambulacral furrows. Like the lily, the stars are not expressed in the anterior-posterior axis and not a "head end". Stars - perfect radial animals.
Very diverse skeletal plates and spines of stars, sometimes transforming into a special superficial organs - peditsillyarii. Under the microscope you can see that the pedicellariae is a group of several elongated "pits" that work like scissors or pliers. These tweezers stars can clean the surface of the body from a variety of fouling organisms, always willing to settle for such convenient "owners".
Most of the stars - predators and corpse-eaters are known, and filter-feeders stars. Not rare, and cannibalism. When you capture a major victim of the stomach is able to turn out the stars of the mouth opening outwards and cover the prey.
The larvae are called stars, and bipinnaria brachiolaria, but there is a star and direct the development, capable of nurturing their own young and care for their offspring. The larvae are able to eat during their development in the plankton, called planktotrophic, not feeding planktonic larvae are called lecithotrophic larvae.
Who knows about 1500 species of sea stars, most of which are inhabitants of tropical seas.
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