Sea Star

Forbes Star, Starfish

Asterias forbesi

Color: Brownish purple to orange with lighter underside.

Size: Up to 12 inches across when mature.

Habitat: Rocky shores, tide pools, dock pilings, Bay bottoms.

Seasonal Appearance: All Year

Sensitivity to Human Action                                              

 

 

MEDIUM

 

 

 

Distinguishing Features and Behaviors:

     Sea stars are not fish as their nickname “starfish” suggests. They belong to a group of animals called echinoderms, which means “spiny skin.” They are related to brittle stars, sea urchins, sea cucumbers, and sand dollars.

     Sea stars have five arms, or rays, connected to a small round body. Sea stars detect light with five purple eyespots at the end of each arm. The bright orange dot in center of the body is called the madreporite. This organ pumps water into the sea star’s body. This pumping action creates suction at the end of hundreds of tube feet, located in paired rows on the underside of the arms. Sea stars use this suction for movement and feeding. They wrap their bodies around hard-shelled clams and other bivalves, using the suction from their tube feet to pull shells apart. When the clam is opened, the sea star pushes its stomach out of its body and into the clam, secreting enzymes that digest the clam’s soft body. The liquefied clam is then absorbed into the stomach. They feed often, and their size depends on the amount of food they eat, not on their age.

     Sea stars are eaten by bottom-dwelling fish and crabs, as well as by sea gulls when low tides leave the sea stars exposed. Similar to other Bay creatures such as lobsters and crabs, sea stars can grow new arms if they lose them. Regeneration will occur as long as one fifth of the sea star’s body remains intact.

     Sea stars breed in the spring, producing as many as 2,500,000 eggs. Females will feel plump and spongy when their arms are filled with eggs.

 

Relationship to People:

     Sea stars pose a threat to commercial and recreational shell fishing efforts. One sea star can devour over 50 young clams in a week. When their population grows, sea stars can consume entire beds of Bay shellfish. In 1929, an oyster company removed more than 10 million sea stars from 11,000 acres of oyster beds in Narragansett Bay.

     Sea stars are harvested with a tool resembling a large mop, which is dragged along the bottom. The sea starts attach themselves to the mop strands and are hauled aboard fishing boats. After removal, the sea stars are ground up and sold for fertilizer and poultry feed.