parent. Teasing out gonadal tissue usually gives material which is not 

 fully ripe. Gonad extract also can be used to stimulate spawning. Venus 

 meraenaria is more resistant than oyster to this method of stimulation. 

 Chemical and electrical stimulation also are possible. Although bivalve 

 larvae can be reared in standing water, stirring is necessary. It is best 

 to change the water frequently. Most bivalve larvae, including quahog, are 

 able to withstand shocks associated with screening and water change. Changing 

 the water is beneficial in controlling bacterial growth and development of 

 toxic metabolites, but water from some sources, such as those containing 

 dinof lagellate blooms, affects development and growth adversely. Larvae 

 thrive on a diet of unicellular algae small enough to be swallowed (less 

 than 10 u) . Provision of an adequate food supply is imperative. Chlorella 

 is adequate. Mixed cultures are unstable and not necessarily reproducible. 

 Algal species differ widely in their food value to bivalve larvae, and some 

 are probably toxic or produce toxic metabolites. Venus meraenaria can 

 develop and grow on a wider variety of foods than can Crassostrea, including 

 Chlorophyceae , Chrysophyceae, and some Cryptophyceae. The relation between 

 amount of food and density of larvae in the culture is important. During 

 dinof lagellate blooms at Milford bivalve cultures failed to grow normally. 

 This may imply presence of toxic metabolites or absence of required substances 

 in seawater; it is extremely difficult to investigate. Larvae of Venus 

 have been reared on mixed algal cultures obtained by adding nutrient salts 

 or commercial agricultural fertilizers to seawater. The organisms were 

 mostly Chlorella, but such mixed cultures are unstable and not necessarily 

 reproducible. Erdschreiber is best (NaN03 O.lg, Na2HP04 0.02g, soil extract 

 50 ml, seawater 1,000 ml. Soil extract: autoclave rich loam and distilled 

 water in proportions of 1 liter water to 1 kg soil) . V. meraenaria is tolerant 

 of many foods provided the cells are- small enough. Chlorophyceae: not all 

 species of Chlorella are good. Cklorella cultures are liable to contain toxic 

 metabolites and overfeeding of larvae will cause death. Chrysophyceae: 

 Isoahrysis galbana, Monoahrysis lutheri, and Chromulina pleiades give excellent 

 growth, they rarely become toxic, and culture methods are well known. 

 Bacillarophyceae and Cryptophyceae are not so satisfactory. Detritus has 

 been tried with Venus Without success. Venus fed a mixture of 4 species gave 

 rather better growth than with single foods. Feeding rates necessary for 

 maximum larval growth: V. meraenaria 10 larvae/ml, Isoahrysis galbana 200 

 cells/mm^/day , Monoahrysis lutheri 250 cells/mm3/day . Epizootic fungus 

 (Sirolpidium zoophthorum) in larval cultures of V. meraenaria can kill most 

 larvae in 2 to 4 days. Despite careful attention to details, some larvae die 

 before metamorphosis, and most mortality is unexplained. Among suspected 

 pathogens are bacteria, colorless flagellates, and ciliates. - J.L.M. 



1926 



Walne, P. R. 1964. 



Sea-water supply system in a shellfish-culture laboratory. U.S. Dept. 

 Interior, Fish Wildl. Serv. , Research Rept. 63: 155-159. 



The system would be suitable for culture of Meraenaria meraenaria. Water 

 is distributed from roof tanks to a tank room where it is heated and enriched 

 with phytoplankton, and to the hatchery where it is filtered and sterilized. 

 Equipment is described. - modified author's abstract - J.L.M. 



1927 



Walne, P. R. 1970. 



Studies on the food value of nineteen genera of algae to juvenile bivalves 

 of the genera Ostrea, Crassostrea, Meraenaria and Mytilus. Ministry Agric. 

 Fish. Food, Fish. Investig. Series II, 26(5), 62 p. 



The food value of algal species was determined by repetitive experiments at 

 various times on bivalves of different parentage. Samples of Meraenaria 

 meraenaria from a few weeks to one year old, ranging in size from 0.6 to 7.0 

 mm, were selected. Samples for each experiment were selected within a narrow 

 size range from the same batch of siblings. Origin of breeding stock was 

 Southampton, England. Growth was measured as an increase in shell size or 

 live weight at various concentrations (usually five) of unialgal cultures in 

 filtered seawater over a span of 3 weeks. In some cases unfiltered sea- 

 water was also used. Relationship between length and live weight was constant. 



535 



