1118 



Loosanoff, Victor L. 1959. 



The size and shape of metamorphosing larvae of Venus (Mercenaria) mercenaria 

 grown at different temperatures. Biol. Bull. 117(2): 308-318. 



Size at metamorphosis has been suggested as one criterion for identification 

 of lamellibranch larvae. Others have maintained that size may be a function 

 of environmental variables. Four experiments were conducted to settle the 

 question for hard clam larvae. Numbers of days required from fertilization 

 to setting varied with temperature from about 20 days (range 16-24) at 18°C 

 to about 7 1/2 days (range 7-9) at 30°C. The relationship appeared to be 

 linear. No significant differences in mean length at setting were found at 

 five temp levels from 18 to 30°C. Extrapolation beyond these limits is not 

 valid, however. The length/width ratio did not change significantly with 

 temp, neither did maximum length. The results should be interpreted with 

 caution, because growth rates and sizes at various stages will vary with 

 amounts and quality of food, or with numbers of larvae per unit volume of 

 water. It had formerly been assumed that eggs and larvae of the southern 

 hard clam, M. eampechiensis , might have just as long a pelagic life as the 

 northern counterpart, M. mercenaria. If so, then eggs of the southern 

 species would cleave and develop more slowly than those of the northern 

 species at a given temperature. To test this, clams of both species were 

 ripened under identical conditions in the laboratory, and fertilized eggs 

 of both were grown at 21°C. Rates of growth were almost identical and 

 setting of larvae began at the same time. - J.L.M. 



1119 



Loosanoff, Victor L. 1960. 



Some effects of pesticides on marine arthropods and mollusks. In Trans. 

 2nd Seminar on Biological Problems in Water Pollution, 20-24 Apr 1959. 

 C. M. Tarzwell (ed.) . U.S. Dept. HEW, Pub. Health Serv., Robt. A. Taft 

 Sanitary Eng. Center, Cincinnati: 89-93. 



Lists about 100 chemicals which are toxic to arthropod predators of oysters, 

 including green crab, Cavcin-id.es maenas , which is also a clam predator. 

 Some of these are also harmful to oysters, especially larvae, but they can 

 be used to create chemical barriers to migration of some predators. Mer- 

 cenaria mercenaria is not mentioned. - J.L.M. 



1120 



Loosanoff, Victor L. 1961. 



Recent advances in the control of shellfish predators and competitors. Proc. 

 Gulf Caribb. Fish. Inst., 13th Ann. Sess., Nov. 1960: 113-128. 



In hatchery trays and troughs an amphipod, Corophium cylindricum , interferes 

 seriously with recently set Venus mercenaria. The amphipod can be 

 exterminated easily with water solutions of several insecticides, such as 

 Guthion, Dipterex, Parathion, Lindane, TEPP and Sevin, at concentrations of 

 1.0 ppm or lower. Such concentrations do not noticeably affect algal 

 cultures, and they do not affect bivalves or other larvae which are fed 

 treated Chlorella. The paper deals principally with predator control on 

 oyster grounds, using water solutions of pesticides, direct chemical 

 treatment, chemical barriers, prevention of fouling, repelling drills from 

 set collectors, baits, and other uses of chemicals. Most treatments and 

 techniques also would be applicable to hard clam. The author recognized that 

 any chemical entering natural waters may be a pollutant, and the review was 

 made with that problem in mind. - J.L.M. 



313 



