FISHERY BULLETIN: VOL. 8.3. NO. 3 



at the periphery of alveoli. Follicle cells completely 

 imbed the oocytes and may fill the lumina of alveoli. 



ACTIVE PHASE. -Enlarging oocytes grow be- 

 tween follicle cells towards the center of alveoli. 

 Oocytes are irregular in shape but are attached to 

 the wall of the alveolus by broad cytoplasmic bases. 



RIPE PHASE. -In the ripe phase, oocytes appear 

 as round cells in the lumina of the alveoli as if free of 

 attachment to the basal membrane, yet they may be 

 attached by a very slender stalk. The large oocytes 

 fill the lumina of the alveoli and are usually more 

 numerous than less developed oocytes. 



PARTIALLY SPAWNED PHASE. -Gonadal 

 tissues contain a few ripe oocytes. Small oocytes are 

 imbedded in follicle cells at the periphery of an 

 empty alveolus. Many alveoli are devoid of ripe 

 oocytes. 



SPENT PHASE. - Very few ripe oocytes are pres- 

 ent, usually darkly staining with obscure nuclei. 

 Numerous spherical droplets of lipoids and other 

 products of cytolysis are characteristic. The spent 

 phase progresses into the inactive phase. 



Male Gonads 



INACTIVE PHASE. -During the inactive phase, 

 male tissues contain products of atypical spermato- 

 genesis (Coe and Turner 1938). Tissues appear quite 

 active, yet this activity will not result in viable male 

 gametes. Pycnotic cells and multinucleated cells ap- 

 pear in the follicles. A few spermatogonia and 

 primary spermatocytes may be seen at the periphery 

 of alveoli while aberrant cells can be seen throughout 

 the alveoli. As indicated in the description of the in- 

 active phase for female gonads, this phase category 

 is expanded to include sexually undifferentiated in- 

 dividuals along with pooled male and female inactive 

 phase animals. 



ACTIVE PHASE. -Proliferating primary sper- 

 matocytes exist at the basal membrane of the alveoli. 

 These are small and uniformly sized cells which are 

 similar to the earliest oocytes. They can be seen 

 growing between follicle cells, extending toward the 

 centers of the alveoli. Early stages of meiosis occur 

 at the periphery of the alveoli, while later spermatids 

 occur at the alveolar centers where they later form a 

 distinct mass. Follicle cells eventually disappear. 



RIPE PHASE. -Masses of spermatozoa arranged 



in more or less radial columns exist in rounded 

 alveoli with tails oriented toward the center. 



PARTIALLY SPAWNED PHASE. -Relatively 



few spermatozoa can be seen. Follicle cells start to 

 refill the alveoli. Some pycnotic cells occur. 



SPENT PHASE. -Spent male tissues contain no 

 or very few spermatozoa in the central alveolar area. 

 Numerous follicle cells with multinucleated cells and 

 pycnotic cells from atypical spermatogenic activities 

 surround small groups of spermatozoa. Tissues lack 

 cells in the active phase of spermatogenesis. The 

 spent phase progresses into the inactive phase. 



RESULTS 



Of the 1,674 clams examined in this study, 1,361 

 were distinguishable as male or female; the remain- 

 ing 313 were indistinguishable as to sex. The male: 

 female ratio (670:691) did not vary significantly from 

 a 1:1 sex ratio (P = 0.25; x" = 0.294). No hermaph- 

 rodites were found. The possibility of asynchrony 

 between males and females was considered. Separ- 

 ate histograms were prepared for the male and 

 female data. Upon visual inspection the histograms 

 showed no clear pattern of asynchrony between the 

 sexes. As no discernable asynchrony was apparent, 

 further analysis was considered unnecessary'. The 

 data for both sexes were pooled and are reported 

 here. 



The clams sampled in this study ranged from 15 to 

 88 mm in shell length. Of the 28 clams < 25 mm 

 sampled, only a single 15 mm female in the active 

 stage could be distinguished, the remainder showing 

 no gonadal activity of any kind, sex being indistin- 

 guishable. 



No consistent relationship between spawning con- 

 dition and size could be discerned for clams over 25 

 mm in length. Correlation coefficients between size 

 and spawning condition were calculated and sub- 

 jected to a ^test, but the results were inconclusive. 

 Clams of all sizes occurred in the various spawning 

 categories throughout the spawning season. Mean 

 shell lengths varied from 44.9 to 61.6 mm among the 

 four populations studied (Fig. 2). 



Candlestick Point 



Sampling began in September 1979 and it was 

 apparent that spawning was ending at that time. 

 While 15% of M. arenaria were still ripe, 65% were 

 inactive and the remaining 20% partially spawned or 

 spent (Fig. 3). By late November, 95% of the clams 



406 



