82 ANIMALS OF THE SEASHORE 



with or without terminal suckers; these are the tube 

 feet — the locomotive organs of the starfish. 



On the upper side of the animal there is a small 

 circular sieve-like structure, frequently colored dif- 

 ferently from the rest of the animal. This is the 

 madreporic plate. Water enters the body of the 

 starfish through this plate and is carried by a series 

 of canals ultimately to the tube feet. A complicated 

 system made up of a valve, reservoir and various 

 muscles regulates the passage of water through 

 these canals and thereby governs the movement of 

 the tube feet. 



Asterias forbesi Desor (Common Starfish) 



PLATE VI. Fig. 1; PLATE VII; Fig. 12 



This is the common starfish of the Atlantic coast 

 from Massachusetts to Florida. Although not 

 abundant along the sandy shores of New Jersey, it 

 thrives on the mussel bottom of many of the fishing 

 grounds offshore; after storms starfish are fre- 

 quently found cast up on the beach. 



The starfish is one of the greatest enemies of the 

 oyster and a great menace to that industry. Every 

 year starfish kill thousands of young oysters and 

 consequently cause a great financial loss to oyster- 

 men all along the coast. 



The starfish's method of attack is unique. It 

 seizes the oyster (or other bivalve) with the tube 

 feet of its opposite arms attached to opposite shells 

 of the oyster. The starfish is then able to exert a 

 tremendous force (more than 1300 grams) and in a 

 short time the muscles of the oyster that keep the 

 shell closed (adductor muscles) become fatigued and 

 relaxed, and consequently the valves hang loosely. 



