method described by Costello et al. (1957). This 

 invalves removing one shell and gill, exposing 

 the visceral mass, and slicing into the gonad 

 which overlays the digestive glands and viscera. 

 Care should be taken to avoid cutting into the 

 underlying intestines and digestive glands, as 

 the presence of body fluids in the cultures of 

 eggs appears to be detrimental to embryonic 

 development. The eggs and sperm are washed 

 into separate collecting containers. Most of the 

 tissue and debris collected along with the 

 gametes can be removed by selective screening. 



Stripped eggs tend to be more irregular in 

 shape than naturally spawned eggs but soon 

 become spherical. Previous investigators 

 (Loosanoff and Davis, 1963) have reported the 

 diameter of spawned mature eggs to average 

 56.5 jj. Our measurements of rounded stripped 

 eggs from ripe clams have agreed with this. 



To fertilize the eggs a small quantity of 

 sperm suspension is added to the egg suspension 

 and mixed by rapid stirring; care must be taken 

 to add only a small quantity of sperm as Spi- 

 siila eggs are quite susceptible to polyspermy at 

 high sperm concentrations (Allen, 1951). Fol- 

 lowing fertilization the germinal vesicle breaks 

 down and a thin membrane forms a short dis- 

 tance above the surface of the egg. 



In conclusion we would like to point out that 

 this is the first time to our knowledge that 

 Spisiila soUdissinia embryos have been reared in 

 synthetic seawater, although they have been 

 previously reared in the laboratory in natural 

 seawater. Not all synthetic seawaters currently 

 available are suitable for this purpose but that 

 developed by Zaroogian, Pesch, and Morrison 

 has consistently given us good results. We feel 

 that the ability to rear these embryos in syn- 

 thetic seawater will enhance the value of surf 

 clam eggs and embryos in embryological and 

 cytological research by offering a standardized 



rearing medium and a comparability of results 

 not always possible when natural seawaters 

 from different locations are used, as well as 

 making possible the use of these organisms in 

 bioassay procedures where the composition of 

 the seawater must be known. 



Literature Cited 



Allen. R. D. 



1951. The use of Spisiila solidissimci eggs in cell re- 

 search. J. Cell. Comp. Physiol. 37:504-505. 

 Costello, D. P., M. E. Davidson, A. Eggers, M. H. 

 Fox, AND C. Henley. 



1957. Mollusca (Pelecypoda) Maciru (now Spisula) 

 solidi.ssinui. In D. P. Costello, M. E. Davidson, A. 

 Eggers, M. H. Fox, and C. Henley, Methods for 

 obtaining and handling marine eggs and embryos, 

 p. 113-116. Mar. Biol. Lab., Woods Hole, Mass. 

 LaRoche, C, R. Eisler, and C. M. Tarzwell. 



1970. Bioassay procedures for oil and oil dispersant 

 toxicity evaluation. J. Water Pollut. Control Fed. 

 42:1982-1989. 

 Loosanoff, V. L. 



1954. New advances in the study of bivalve larvae. 

 Am. Sci. 42:607-624. 

 Loosanoff, V. L., and H. C. Davis. 



1963. Rearing of bivalve mollusks. In .Adv. Mar. 

 Biol. 1:1-136. 

 Ropes, J. W. 



1968. Reproductive cycle of the surf clam, Spisula 

 solicli.ssinia, in offshore New Jersey. Biol. Bull. 

 (Woods Hole) 135:349-365. 

 Yancey, R. M., and W. R. Welch. 



1968. The Atlantic Coast surf clam — with a partial 

 bibliography. U.S. Fish Wildl. Serv., Circ. 288, 14 p. 



Zaroogian, G. E., G. Pesch, and G. Morrison. 



1969. Formulation of an artificial seawater media 

 suitable for oyster larvae development. Am. Zool. 

 9:549. 



Wayne D. Cable 

 Warren S. Landers 



Middle Ailaiuic Cousud Fisheries Center 

 Milford Laboratory 



National Marine Fisheries Service, NOAA 

 Milford. CT 06460 



249 



