fungicidal antibiotic Malucidin reduced survival and growth of clam larvae even 

 at concentrations at which it did not affect fungus. Streptomycin increased 

 clam larval growth, but above a concentration of 1/1,000 growth decreased. 

 Survival of streptomycin-treated larvae was only slightly better than that of 

 controls. Effects of aureomycin were similar to those of streptomycin, but 

 larval growth increases were less, with optimum at 3.2 ppm. At 320 ppm 

 mortality of larvae was complete. Terramycin caused 100% mortality at con- 

 centrations of 1 ppm. Sulfa drugs tested did not accelerate survival and 

 growth of clam larvae, and some reduced growth rates at concentrations tested. 

 Larvae cultured in dinof lagellate blooms, or exposed to blooms in the natural 

 environment developed abnormally and few grew into normal straight-hinge 

 larvae. It was believed that the effects were caused by dissolved substances. 

 Very low tolerances of oyster and clam embryos and larvae to many substances 

 tested suggests that dissolved substances may be more important than formerly 

 recognized in success or failure of oyster and clam spawning. (Abstracter's 

 note: some experiments appear also to confirm the greater resistance of hard 

 clam larvae to environmental change, as compared with oyster larvae.) - D.L. 

 and J.L.M. 



447 



Davis, Harry C, and Robert R. Guillard. 1958. 



Relative value of ten genera of micro-organisms as foods for oyster and 

 clam larvae. U.S. Dept. Interior, Fish Wildl. Serv. , Fish. Bull. 58: 

 293-304. 



A mixture of the Chrysophyceae Isoehrysis galbana and Monochrysis lutheri 

 with Chlorophyceae Platymonas sp. and Dunaliella euahlora provided better 

 growth of Mercenaria mercenaria larvae than did equal quantities of any of 

 single-species foods. Chlorococcum sp. , Isochrysis, and Monochrysis were 

 the 3 best single foods for clam larvae. Clam larvae can utilize several 

 forms having cell walls, even from earliest larval stages. Stichococcus 

 sp. and Prymnesium parvum , both highly toxic, were the only microorganisms 

 tested that had no food value for clam larvae. Isoehrysis showed no 

 toxicity even at highest concentration tested. Optimum concentration of 

 Isochrysis was at least double that of Chlorella. It was concluded that 

 Isochrysis and Monochrysis produce little if any toxic metabolites. 

 Presence and perhaps thickness of cell walls and degree of toxicity of 

 external metabolites are probably important factors in determining 

 usability of microorganisms as foods for bivalve larvae. - modified authors' 

 summary - J.L.M. 



448 



Davis, Harry C, and Herbert Hidu. 1963. 



Effects of pesticides on eggs and larvae of oysters (C. virginica) and clams 

 (V. mercenaria) . Proc. Natl. Shellf. Assn. 52, August 1961: iii. 



Listed by title only. - J.L.M. 



449 



Davis, Harry C, and Herbert Hidu. 1969. 



Effects of pesticides on embryonic development of clams and oysters and on 

 survival and growth of the larvae. U.S. Fish Wildl. Serv., Fish. Bull. 

 67(2): 393-405. 



Fifty-two compounds were tested for their effects on embryos of hard clam, 

 Mercenaria mercenaria, American oyster, Crassostrea virginica, and on their 

 larvae. Pesticides included 17 insecticides, 12 herbicides, one nematocide, 

 four solvents, and 18 miscellaneous bactericides, fungicides, and algicides. 

 Most compounds affected embryonic development more than survival or growth 

 of larvae. Some, however, drastically reduced growth of larvae at con- 

 centrations that had relatively little effect on embryonic development. It 

 is necessary, therefore, to evaluate the effects of pesticides on all stages 

 of the life cycle of an organism before the pesticide can be considered safe. 

 Nevertheless, differences in toxicity to bivalve larvae among compounds of 



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