Semelidae 543 



1927. Report of experimental shellfish station. Report, Conservation De- 

 partment, State of New York, 1926 (1927): 1-26. 



Order teleodesmacea, Family semelidae 



CUMINGIA TELLINOIDES 



Benjamin H. Grave, De Pauw University 



Cumingia tellinoides is a small lamellibranch mollusk found abun- 

 dantly in the Woods Hole region but in restricted areas only. The 

 breeding season extends from the first or second week in June to about 

 August 20. Eggs in small quantities may be had in September. The 

 time of spawning by Cumingia in its natural habitat is influenced by 

 two environmental factors. This species occurs in shallow water and 

 when it becomes heated by a period of unusually warm days nearly all 

 females spawn. On the other hand, if the environment remains normally 

 uniform, heavy spawning takes place at the period of the full moon and 

 the days immediately following. The lunar periodicity may be obscured 

 if general spawning due to rapidly rising temperature has already oc- 

 curred. It should be remarked that spawning is rarely 100% at any 

 time, so that eggs from a few females are obtainable almost any day in 

 the summer. However, if records of the percentage number of females 

 spawning are kept at frequent intervals the periodic character of the 

 spawning will be evident.* 



Experiments have shown that each female spawns several times during 

 the summer and that the gonads are again filled with eggs within a 

 short time after spawning takes place. Eggs are not again obtainable 

 except in very small amounts for a period of ten days after spawning 

 has occurred. It has been shown that the germinal epithelium is 

 active throughout the breeding season and the production of eggs and 

 spermatozoa is a continuous process. 



METHOD OF OBTAINING EGGS IN THE LABORATORY 



Wash the animals free from all sediment and isolate them in small 

 stender dishes half filled with seawater. When so placed in seawater and 

 left undisturbed for an hour, or sometimes less, they extend their siphons 

 and spawn if sexually mature. Eggs or sperm, as they accumulate in the 

 supra-branchial chambers, are thrown forcibly from the dorsal siphon. 

 The sexes are separate and may be distinguished by their color. The 

 males are white and the females pink. The shell is not heavy so that 

 the color of the gonads shows through more or less. 



Cumingia may not be kept in the laboratory indefinitely. It is de- 



*See Abstract No. n, A nat. Rec. 44:198. 



