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The common sea star, Asterias forbesi, belongs to the Phylum Echinodermata, marine animals whose most striking characteristic is their radial symmetry. The phylum includes sea cucumbers, sea lilies, sea urchins and brittle stars. This particular species occurs in the saltier waters near the mouth of the Chesapeake Bay, in tide pools, along pilings, jetties, and on sandy or rocky bottoms, and belongs to the class Stelleroidea. Asterias forbesi preys on bivalve mollusks and other marine animals and is capable of consuming significant quantities of oysters and scallops.
The common sea star inhabits the low-tide line to water 160 deep. Its geographic range extends from the Gulf of Maine to Texas. Fishermen dredging in the deeper waters near the Bay mouth often take Asterias forbesi along with their catch. Like other, similar species Asterias forbesi is a star-shaped, somewhat flattened body with five arms, a rough surface with small bumps or spines and a bright orange or yellowish eyelike organ at the center-actually a sieve plate or madreporite-through which water enters the animal's vascular system. The underside is pale, with the mouth at the center, and each arm is grooved and bordered by four rows of tiny, tubular 'feet'. The sea star uses the suctioning capacity of its feet both for locomotion-by grasping and releasing fixed surfaces-and for feeding.
Asterias forbesi can grow to have a radius of 5 1/8 inches and has long arms, usually ranging in color from tan and olive to orange, red or pink. Its sieve plate is usually orange. Its limy skeleton is firm and its spines are broadly scattered over its surface, not arranged in symmetrical rows. When a sea star loses or damages an arm, it sheds the appendage close to the center of its body and the cut skin begins to heal over. From this point the animal regenerates a new limb. Sometimes a sea star will overcompensate and grow more than one limb to replace the maimed or lost limb.
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The
term echinoderm means 'spiny-skinned', and refers to the calcareous
skeleton that projects through the animal's skin. All members of Echinodermata
possess a water vascular system that enables most of their metabolic
functions. This 'hydraulic' system helps pump the organism's appendages
full of fluid so that they can move and also enables the animal to feed.
It flushes the major internal anatomical cavities that contain their
nervous, digestive and reproductive systems, enabling metabolic wastes
to leave the body without the aid of a separate excretory system. 
Even
sea stars with a three-inch radius can exert a 12-pound pull using their
tubular feet. To attack and consume a clam, mussel or oyster, the sea
star attaches two of its arms to one valve and three to the other. It
forces a small opening-just .1 mm will do-and then projects, or 'everts',
part of its stomach through its own mouth opening and into the bivalve's
opening, secreting digestive juices, which begin to consume the prey's
soft tissues. The mollusk dies, its valve gapes, and the sea star consumes
the rest. Sea stars don't confine their interest to bivalves but will
also eat snails and barnacles. 
