FISHERY BULLETIN: VOL. 82, NO. 2 



again lacked obvious spermatogenic cells (Fig. 9a, 

 b). Oocytes in females were at the same stage of 

 development as seen for females with sparse 

 gonadal tubules, but more were growing from the 

 germinal epithelium and some portions of the 

 germinal epithelium lacked obvious oogenic cells 

 (Fig. 9c, d). 



The sexually mature condition was found in 19 

 males and 9 females. In these quahogs the tubules 

 were greatly expanded and filled the gonadal area; 

 little connective tissue occurred between adjacent 

 tubules. Developmental stages similar to those de- 

 scribed for other bivalves by Ropes and Stickney 

 ( 1965) were recognized. Two males and one female 

 were in an early gonadal condition. Sper- 

 miogenesis and oogenesis had cellular charac- 

 teristics as in gonads of moderate tubule develop- 

 ment, but the tubules were more numerous and 



crowded together. Six males were in a late gonadal 

 condition. Primary and secondary spermatocytes 

 and spermatids were proliferating from the ger- 

 minal epithelium, filling about half of the tubules 

 and sperm crowded into the lumina. No females 

 were found in the late gonadal condition, but 11 

 males and 2 females were in an advanced late 

 stage. In males, spermatocytes and spermatids 

 proliferated from the germinal epithelium and 

 sperm predominated in the lumina of the tubules 

 (Fig. 10a, b). In females, oocytes crowded into the 

 lumina of tubules and a few seemed to be attached 

 to the germinal epithelium. No ripe males and 

 only six ripe females with numerous ripe oocytes 

 crowding into the tubules were found (Fig. 10c, d). 

 The potential for developing large numbers of 

 germinal cells was most evident and indicative of 

 full sexual maturity in all of these quahogs. 



a 



,< 



, 



v . 



% 



: S 



 



m 



V 



\ *>. 



V 



I 







/"** 



■AS'4 





3< 







.•SO*- 'ft** 



SI 





*? 



'■ 



V 

 t. 



* 







lOO^m* 





d 





&-?§£# U 





u 



FIGURE 9. — (a) Differentiated gonadal tissue section in the moderate condition from a 7-yr-old ocean quahog, Arctico islandica, 42.9 

 mm shell length, (bi Enlargement of spermiogenesis in a portion of a gonadal tubule, ic) Differentiated gonadal tissue section in the 

 moderate condition from an 8-yr-old female ocean quahog, 43.3 mm shell length, (d ) Enlargement of oogenesis in a portion of a gonadal 

 tubule. 



262 



