720 



Grigg, Richard W., and Robert S. Kiwala. 1970. 



Some ecological effects of discharged wastes on marine life. Calif. Fish 

 Game 56(3) : 145-155. 



Mercenaria meraenaria is not mentioned. - M.W.S. 



721 



Guberlet, J. E. 1925. 



Malacobdella grossa from the Pacific coast of North America. Pub. Puget 

 Sound Biol. Sta. 5: 1-13. 



Including commensals in Meraenaria meraenaria. - J.L.M. 



722 



Guillard, R. R. 1958. 



Some factors in the use of nannoplankton cultures as food for larval and 

 juvenile bivalves. Proc. .Natl. Shellf. Assn. 48: 134-142. 



This paper is based on feeding experiments with larval and juvenile oysters 

 and Venus mercenaria in 1956 and 57. It is full of detailed information and 

 thus difficult to reduce to an abstract. Food quantity is considered a 

 relatively simple question. Quantity and concentration are important. 

 Larvae are maintained at concentrations of 3 to 15/ml, while phytoplankton 

 concentrations vary from 10 to 100 thousand cells/ml, depending on size of 

 cells. Careful studies of phytoplankton concentrations in nature show that 

 they approach these laboratory concentrations at times. In Great South Bay, 

 N.Y. undesirable blooms of Stiohoooaaus and Nannoahloris exceeded 2x10^ cells/ 

 ml at times. Juveniles seemed to do fairly well on about 3 times the rate fed 

 to larvae. The right kind of food is more important and difficult. Growth 

 of animals is the only criterion by which value can be measured at present. 

 Clam larvae can use more foods than oyster larvae can, and juveniles can 

 utilize an even wider range of foods. Chrysophytes and diatoms were 

 especially good for juveniles. Naked flagellates that were best for larvae 

 were relatively good also for juveniles, but cryptomonads were useless to 

 larvae. Factors other than nutritive content affected acceptability. 

 Presence and thickness of algal cell walls and production of toxic substances 

 by algae were important. Best results will be obtained by using a mixture of 

 cultures of 2 or 3 small naked flagellates, especially chrysophytes, for 

 larvae, and supplement this with cryptomonads and diatoms for juveniles. Use 

 of cultures rather than natural phytoplankton creates another problem. 

 Impure cultures may be toxic under certain circumstances. Sometimes larvae 

 may grow normally to straight-hinge stage, then die. It is believed that 

 toxicity is caused by bacteria that get into cultures during handling. 

 Erratic results in feeding experiments tend to coincide with use of impure 

 cultures, especially at room temp. Algal cultures should be started from 

 bacteria-free stocks and grown at the lowest temp that provides rapid growth. 

 - J.L.M. 



723 



Guillard, Robert R. L. 1959. 



Further evidence of the destruction of bivalve larvae by bacteria. Biol. 

 Bull. 117 (2) : 258-266. 



Various organisms, like the fungus Sirolpidium , can destroy clam larvae in 

 experimental cultures, but evidence that bacteria are harmful has been 

 largely circumstantial. This paper presents evidence that two clones of 

 bacteria isolated from an infected Venus mercenaria larva destroyed healthy 

 larvae, while other clones did not under similar conditions. In final 

 experiments larvae were reared under aseptic conditions, excluding the 

 possibility that contaminating microorganisms were the direct cause of 

 death and bacteria were secondary invaders. Available evidence favors the 

 hypothesis that the mechanism was invasion or contact, not an exotoxin 

 liberated into the medium. It is not implied that bacterial metabolites are 

 without influence, for high concentrations stopped growth of clam larvae 

 entirely. Bacteria in algal food cultures sometimes caused abrupt decrease 



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