552 



Epifanio, C. E. 1979. 



Growth in bivalve molluscs: Nutritional effects of two or more species of 

 algae in diets fed to the American oyster Crassostrea virginica (Gmelin) and 

 the hard clam Mercenaria mercenaria (L.) . Aquaculture 18: 1-12. 



Mercenaria mercenaria were fed 15 different diets composed of various mix- 

 tures of four species of algae {Carteria chui, Isoehrysis galbana, Platymonas 

 suecica, and Thalassiosira pseudonana) for 6 weeks. Growth of hard and soft 

 tissue was not correlated with gross chemical (protein, lipid, carbohydrate, 

 or ash) or amino acid composition of the diets, but was related to presence 

 or absence of particular algal species. Growth was generally least in diets 

 containing large proportions of C. chui and greatest in diets containing 

 large amounts of I. galbana or T. pseudonana. Diets containing I. galbana 

 and T. pseudonana invariably supported greater growth than diets consisting 

 of either species, indicating synergism in the relative food values of the 

 species. P. suecica was a relatively poor food when used as the sole com- 

 ponent of the diet, but its food value was markedly increased when fed in 

 combination with either or both I. galbana and T. pseudonana. One possible 

 explanation could be that C. chui and P. suecica are deficient in some growth 

 promoting micronutrient found in relatively high quantities in I. galbana 

 and T. pseudonana . If this acted in such a way that a threshold quantity 

 were necessary for growth but that additional quantities did not increase 

 growth, then nonadditive effects might be expected in diets combining defi- 

 cient with replete algae. An alternative explanation involves the relative 

 digestibility of various algal species. - J.L.M. 



553 



Epifanio, C. E. 1979. 



Comparison of yeast and algal diets for bivalve molluscs. Aquaculture 16(3): 

 187-192. 



Growth of young Mercenaria mercenaria (initial dry weight 10 mg soft tissue) 



was comparable to that of controls when the diet contained up to 50% yeast. 



It is clear that Candida utilis can replace 50% of the algae without loss. 

 - J.L.M. 



554 



Epifanio, C. E., and R. F. Srna. 1975. 



Toxicity of ammonia, nitrite ion, nitrate ion, and orthophosphate to 

 Mercenaria mercenaria and Crassostrea virginica. Mar. Biology 33: 241- 

 246. College of Marine Studies, Univ. Delaware, Newark, Del. - DEL-SG-5-76. 



Surprisingly high tolerance toward chemicals tested was exhibited by both 

 bivalve species. Juveniles and adults were about equally tolerant. Lethal 

 and sublethal responses were tested. Highest concentrations tested on M. 

 mercenaria were 8x10~2m NH 4 C1, 10xl0~ 2 M NaN0 2 , 32xlO _2 M NaN0 3 , and 6xl0 _4 M 

 Na3PC>4. Ninety-six hour mean lethal tolerance limit (TL„) of M. mercenaria 

 ranged from 1.1 to 1.6xlO -2 M (110 to 172 mg/1) for ammonia and 8.1 to 

 8.5xl0~ 2 M for nitrite. Tolerances to nitrate and orthophosphate were so 

 high as to make definition of a 9 6-hr TL m ecologically meaningless. Sub- 

 lethal effects were measured by rate of removal of the planktonic alga 

 Isoehrysis galbana from the water. Sodium phosphate did not affect feeding 

 rates over the entire range tested, but each of the other 3 chemicals did. 

 It was concluded that M. mercenaria is very unlikely to be exposed to 

 acutely toxic concentrations of the 4 chemicals in the natural environment. 

 Effluents even of secondarily treated domestic sewage rarely contain levels 

 as high as the 96-hr TL m reported. - J.L.M. 



155 



