17. What do oysters and clams eat? 



Oysters and clams eat microscopic plants called phytoplankton, which 

 live in the water. Oysters and clams spend most of their time attached 

 to or buried in the bottom and do not move around searching for food. 

 They obtain food by pumping water through their bodies. Clams and 

 oysters, like fish, breathe by means of gills, but their gills also act as a 

 sieve, straining the phytoplankton out of the water. The gills are cov- 

 ered with a sticky substance which holds the phytoplankton. Tiny 

 hairs, called cilia, move the food from the surface of the gills to the 



mouth. Pieces of food too large for the animal to eat are discarded and 

 flushed out of the body by the water current. A single blue mussel will 

 pump about 10 gallons of water a day, filtering out the plankton and 

 debris that make up its diet. 



Of the various nutrients that have been experimentally tried as food 

 supplements for oysters, finely ground corn meal was found to be ac- 

 ceptable and resulted in fatter oysters. 



Barnes, Robert D. 



Invertebrate Zoology, W. B. Saunders Company, 1964. 



Cromie, William J. 



The Living World of the Sea, Prentice-Hall, 1966. 



Galstoff, P. S. 



"The American Oyster (Crassostrea virginica Gmelin)," U. S. De- 

 partment of the Interior, Fisheries Bulletin 64: 1-480, 1964. 



17 



