Collection and Maintenance of 

 Surf Clams in the Laboratory 



Although some information on the collection 

 and maintenance of surf clams in the labora- 

 tory and their reproductive cycle has been pub- 

 lished (Loosanoff antl Davis, 1963; Ropes, 1968; 

 Yancey and Welch. 1968), we feel it pertinent 

 to this pai)er that it be reviewed and our own 

 observations added. 



Adult surf clams can be purchased from bio- 

 logical supi)ly houses or collected in their nat- 

 ural habitat. The range of S. soUdissuiia is 

 along the Atlantic Coast of North America, from 

 the Gulf of St. Lawrence to Cape Hatteras 

 (Yancey and Welch, 1968). South of Cape Hat- 

 teras the surf clam is represented by Spi>inla 

 solidissinta raveiieli. similar to S. soUdissima 

 but a smaller species. S. soUdissiiua is found in 

 sandy bottoms from the low-tide line to depths 

 of 500 ft in waters of oceanic salinity. They are 

 present in shallow water beds, at various points 

 along their range, and are easily hand-gathered 

 along the coasts of Delaware, New Jersey, Long 

 Island (New York), Rhode Island, and Massa- 

 chusetts. Our collections have come mainly from 

 Little Narragansett Bay and the area of Point 

 Judith, in Rhode Island. 



Surf clams can also be obtained from com- 

 mercial clam boats working the beds, but our 

 observations have shown that hand-gathered 

 clams are more suitable for laboratory purposes; 

 those obtained from commercial sources are 

 often damaged by the action of the hydraulic 

 dredge used in harvesting. They suffer high 

 mortalities soon after introduction into the 

 laboratory and long-term survival of those re- 

 maining also seems inferior to that of hand- 

 gathered stocks. 



We feel that the best working size for labora- 

 tory animals to be used as a source of gametes 

 is 4 to 5 inches. Larger ones require more space 

 and do not survive as well in crowded tanks. 

 Smaller animals are more difficult to spawn, 

 even though we have found some specimens as 

 small as 5 cm to have viable sex products. 



Ropes (1968), in a study of the rej^roductive 

 cycle of offshore surf clam populations, found a 

 biannual cycle during 3 years of the 4-year 

 period covered by his study. This biannual cycle 

 was characterized by a major mid-year spawn- 

 ing and a minor late-year spawning. He found 

 ripe clams as early as May and as late as Octo- 



ber during 3 years of the study. This pattern of 

 ripeness may vary between inshore and off- 

 shore populations, depending on local tempera- 

 ture conditions. We found ripe clams only from 

 June to August in inshore Rhode Island waters. 



Surf clams can be collected prior to their 

 natural spawning period and conditioned to 

 ripeness in the laboratory. Conditioning refers 

 to a procedure of gradually raising the water 

 temperatures at which bivalves are maintained 

 as a means of achieving gonad ripeness prior 

 to the time one would expect to find ripe ani- 

 mals in the field (Loosanoff, 1954). 



We have collected animals with unripe 

 gametes from early winter through late spring 

 (December to May) and conditioned them at 

 15 °C. This temperature equals or exceeds that 

 at which gametogenesis takes place in natural 

 populations (Ropes, 1968). Such animals col- 

 lected in early winter and conditioned in the 

 laboratory have been spawned as early as 

 March. 



Ripe surf clams held in the laboratory at 15 °C 

 have never spawned spontaneously; thus, the 

 spawning threshold of this animal in the labo- 

 ratory would appear to be higher than 15 °C. We 

 do feel, however, even though we, as yet, lack 

 quantitative data to substantiate it, that ripe 

 animals held at 15 °C tend to resorb their 

 gametes more quickly than those held at a 

 lower temperature following conditioning. Ripe 

 animals collected in June and held at 10°C con- 

 tained viable sex products in December. 



Ropes (1968) reported that offshore popula- 

 tions spawn at lower temperatures than we 

 found in our laboratory populations. He also 

 noted that abrupt rises in water temperature 

 were not clearly a cause of spawning in natural 

 populations. A rapid increase in temperature is 

 certainly an important factor in stimulating 

 spawning in the laboratory. Clams conditioned 

 at 15 °C spawned when the temperature was 

 raised quickly to 18-20 °C. However, these clams 

 were less responsive than those held in damp 

 refrigeration (approximately 2°C, covered with 

 a wet towel to prevent drying) overnight prior 

 to exposure to 18-20 °C. Refrigerated clams nor- 

 mally spawned within an hour after exposure 

 to 1*8-20°C, while those conditioned at 15°C 

 and exposed to water at 18-20°C did not. 



Eggs and sperm can also be obtained by strip- 

 ping the sex products from the gonads using a 



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