HOWELL: SEASONAL CHANGES IN YELLOWTAIL FLOUNDER OVARIES 



Type I — Corpora atretics (Fig. 3B): Large and 

 irregularly shaped. Size variable, but generally 

 from 150 to 300 /Am. Characteristics similar to 

 either early maturing or late maturing oocytes ex- 

 cept that the zona radiata is broken and collapsed 

 inward. Follicle cells are hypertrophied, lightly 

 basophilic, and invade the cytoplasm. Com- 

 paratively few yolk globules remain, and those 

 present are indistinct. Found only in prespawn- 

 ing fish. 



Type II — Resorbing (Fig. 3C): Cytoplasmic charac- 

 ters similar to those of either late maturing or 



hyaline oocytes. Entire cell is collapsed inward, 

 and zona radiata is broken in numerous places. 

 Found only in postspawning fish. Size variable, 

 but generally from 350 to 400 iim. 



Seasonal Changes in 

 Microscopic Appearance 



When the relative abundances of the different 

 developmental stages of oocytes were calculated for 

 each sampling date, seasonal differences were ap- 

 parent (Table 4; Figs. 4, 5). The mean diameter of 

 some oocyte types also showed seasonal changes 



B 







U"> 



§ fRI 



C *.% *^M *M 





FIGURE 3.— A. Hyaline oocyte of the yellowtail flounder. B. 

 Corpora atretica in a ripening fish. C. Resorbing oocyte in a 

 spent fish. C A = corpora atretica, f = hypertrophied follicle 

 layer, HY = hyaline oocyte, io = immature oocyte, LM = late 

 maturing oocyte, lp = late perinucleolus oocyte, RE = resorb- 

 ing oocyte. 



347 



