and unsterilized detritus labeled with carbon to determine if they 

 assimilated either the detritus per se or its associated bacteria as 

 food. 



All three species ingested and assimilated detritus. After three 

 days of feeding, a small gastropod, Bittium varium , had ingested and 

 assimilated more detritus per mg of body weight than either the 

 grass shrimp, Palaemonetes pugio , or the polychaete, Glycera dibranchiata . 

 Both Palaemonetes and Bittium assimilated carbon from labeled bacte>'ia 

 associated with the detritus as well as from the labeled detritus. 

 All three species assimilated some carbon from soluble sources. 



On the basis of the data presented, it appears that detritus may be 

 an important food source for these animals in nature since all three 

 species assimilated more carbon from detritus than from undecomposed 

 eel grass. Because these animals are able to assimilate detritus and 

 because detritus is ^^ery abundant in the eel grass beds where they 

 are the dominant species, the detritus could be one of their main sources 

 of energy. (A. A. and summary) 



Keywords: detritus, macrofauna, food chain, estuaries 



III-E-11 



Kost, A.B., and A.W. Knight. 1975. The food of Neomysis mercedis Holmes 



in the Sacramento-San Joaquin estuary. California Fish and Game 



61(l):35-46. 



Gut contents were determined in approximately 1,500 opossum shrimp 

 from the Sacramento-San Joaquin estuary. The shrimp, obtained 

 from 12 stations over a 13-month period, were 2 to 17 mm long. The 

 most abundant items in the gut were detritus and diatoms. Origin of 

 the detritus was not determined. The percentage of detritus relative 

 to diatoms was greater in winter than in summer and increased with shrimp 

 size. Of the 40 kinds of diatoms encountered in the guts of opossum 

 shrimp, two diatoms--Coscinodiscus and Melosira--were far more abundant 

 than the rest. The former was the most important diatom in the guts 

 of shrimp from the lower Delta and Suisum Bay stations. 



Previous reports indicate that mysid shrimp are capable of utilizing 

 a wide variety of foods. The results of this study are consistent 

 with these reports. (L.H.) 



Keywords: estuaries, opossum shrimp, diatoms, California 



128 



