312 



Fishery Bulletin 102(2) 



A No yolk in oocytes 



86 mm 15 g 



5646 Total oocytes 



ova 



0.719 = C 



2.0 2.5 3.0 



300 



100 



B Begun yolking 



112 mm 39 g 



44 10 Total oocytes 



ova 



0.711 = C 



JUiiLl 



i i - 1 1 1 1 1 1 1 1 1 > < 



2.5 3.0 



C Before 1st spawn - no POF 



122 mm 39 g 



3724 Total oocytes 



ova 



0.694 = C 



0.5 1.0 1.5 2.0 



600 

 500 

 400 

 300 

 200 

 100 

 



600 



500 

 400 

 300 

 200 

 100 

 



D 2 stages of POFs 



137 mm 50 g 



2988 Total oocytes 



88 ova 



0.667 = C 



..Illllllllllllll.ll.lh.lJ.. I..II. IllMl.... 



1.0 1.5 2.0 2.5 3.0 



E 3 stages of POFs 



133 mm 45 g 



1 642 Total oocytes 



1 446 ova 



0.574 = C 



■■lllllllllllH I ■■■■•■ "iHl--!  



100 

 



2.5 3.0 0.5 



Oocye major axis diamter (mm 



F Diver caught - Dying 



1 36 mm 33 g 



1 487 Total oocytes 



ova 



0.544 = C 



lillllllllilililn.iiiinl.lii.,liiiii..i 



1.0 1.5 2.0 2.5 



3.0 



Figure 6 



Oocyte-size distribution for six female Loligo opalescens. Dorsal mantle length (mm), 

 body weight (g), the total number of oocytes in the ovary, and the number of ova are 

 indicated for each specimen. (A) Female that is immature. (B and C) Females that 

 are considered to be mature and preovulatory because neither has postovulatory fol- 

 licles (POFs) in their ovaries nor ova in their oviducts. Although the oocytes have just 

 begun yolking in the ovary of female B, female C has well-yolked oocytes and is close 

 to its first ovulation. (D-F) Females are mature spawning females and their ovaries 

 contained postovulatory follicles. Female F was caught by a scuba diver and appeared 

 to be dying. 



same conclusion from their histological analysis of L. opal- 

 escens ovaries. Thus, potential fecundity in L. opalescens 

 probably becomes fixed near the onset of spawning. Not 

 all oocytes are deposited, however, because all spawning 

 females had some oocytes and many oocytes were counted 

 in the ovary of a dying female (Fig. 6F). 



In L. opalescens the migration of the oocyte nucleus 

 begins early in the maturation process shortly before the 

 onset of vitellogenesis, whereas in fishes, migration is 

 near the end of vitellogenesis. The follicle of a migratory- 

 nucleus-stage oocyte (late stage IV) of L. opalescens has a 

 very large granulosa cell layer (in relation to the size of the 

 oocyte) and is highly folded and perhaps fully developed. 

 Subsequent maturation of the oocyte seems to consist 

 primarily of the massive addition of yolk and fluid and the 

 consequent stretching and unfolding of the follicle, ending 



with the formation of a chorion. Apparently, the formation 

 of the chorion compacts the yolk because many mature 

 oocytes (endpoint of stage V) have a smaller major axis 

 than advanced yolked oocytes prior to chorion formation. 

 Thus, maximum oocyte size is not a good proxy for oocyte 

 maturation in L. opalescens and is not an indicator of the 

 time remaining before spawning of the next batch. More 

 importantly, the ovary of L. opalescens seems well adapted 

 for rapid oocyte vitellogenesis, maturation, and spawning 

 because nuclear migration and follicle cell proliferation is 

 completed at an early stage. 



Ovulation appears to occur in small batches. The distri- 

 bution of oocyte sizes in spawning L. opalescens was flat 

 (e.g., Fig. 6, D-F) and lacked the separate and distinct mode 

 of hydrated oocytes that is typical in fishes. Batch sizes of 

 mature oocytes ranged from 5 to 246 and averaged 50 (n =72 



