1102 



Loosanoff, Victor. 1936. 



Sexual phases in the quohog (sic). Science 83(2151): 287-288. 



Young Venus mercenaria , 0.6 to 0.7 cm long, collected from Long Island Sound 

 near Milford, Conn, in October, had distinctly bisexual gonads with very 

 strong male predominance. Most had fully ripe spermatozoa in the central 

 part of the lumen, and small ovocytes and indifferent gonia in the inner 

 walls of the follicles. Apparently functional spermatozoa are found in 

 follicles of many young clams throughout winter. The following spring the 

 follicles are gradually extended until they occupy spaces around the stomach 

 and between the digestive gland and the muscular body wall. Many animals at 

 this stage may be taken for true males, but presence of young ovocytes with 

 mitochondrial bodies and yolk nuclei indicated the bisexual character of 

 gonads. When water temp reaches the critical point in midsummer, ripe 

 spermatozoa are discharged. Soon after, 2 distinct types of individual are 

 distinguishable as definitive males and females. In males a 2nd period of 

 spermatogenesis begins in autumn and continues slowly through winter. 

 Spermatozoa are discharged late the next summer at a shell length of 3 cm or 

 more. Those young destined to become females have follicles with empty 

 lumina as sperms are discharged. At the end of the initial male phase the 

 follicles remain distended with only a thin layer of undifferentiated cells 

 and small ovocytes along the inner walls. Numerous phagocytes usually invade 

 the follicles and devour the pycnotic and degenerated male cells. Ovogenesis 

 begins in spring and follicles contain mature ova in June and July. With few 

 exceptions, adults are of separate sexes, although gonads of most adult males 

 contain small ovocytes somewhere along the walls of the follicles. Adult 

 males contain mature sperms at all times except for a short post-spawning 

 period. Adult females also contain large ova at all seasons. Thus, primary 

 gonads of V. mercenaria are protandric, although not exclusively so. A few 

 individuals develop into females without passing through a functional male 

 phase. - J.L.M. 



1103 



Loosanoff, Victor L. 1937. 



Spawning of Venus mercenaria (L. ) Ecology 18(4): 506-515. 



Spawning of hard clam in Long Island Sound occurred at temperatures below 

 24.0°C. In the lab, spawning occurred at temperatures from 23. 0°-30. 2°C. 

 Most males spawned at 25.0-26.0°C and most females at 29.0°C. At 

 temperatures 25.0-30.0°C it took longer to induce females to spawn than 

 males. The latent period of spawning reaction is generally shorter at 

 higher temperatures. No method was found to induce spawning at temp- 

 eratures lower than 23.0°C. Only a few times did raising of water 

 temperature or addition of gametes or both induce spawning. Attempts to 

 fertilize eggs artificially extracted from female clams were unsuccessful. 

 - D.L. 



1104 



Loosanoff, Victor L. 1937. 



Development of the primary gonad and sexual phases in Venus mercenaria 

 Linnaeus. Biol. Bull. 72(3): 389-405. 



Examination of hard clams from Long Island Sound showed a primary bisexual 

 gonad formed when the clam length was 4-6 mm. Primary gonad formed from 

 associations of germinal cells in the connective tissue at the level of or 

 slightly below the heart. Lumen soon appeared in gonad follicle, and 

 germinal cells began rapid proliferation. Primary gonad contained 

 antecedent cells of both sexes but its protandric nature was manifested 

 by rapid proliferation of spermatogenic cells. A few individuals developed 

 as females without passing through a functional male phase. Functional 

 spermatozoa were seen in gonads of 5-7 mm clams in October and November. 



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