WYLLIE ECHEVERRIA: REPRODUCTION OF CALIFORNIA HOCKFISHES 



the ovary swells in size. The eggs remain opaque, 

 and held within a follicle. 



Fertilized eggs (Gonad Stage 4) are about 0.9 mm 

 in diameter and have shed their follicles, and the 

 yolk globules have disintegrated. Externally the 

 eggs appear translucent yellow or white and are no 

 longer held in tight grapelike clusters. They are held 

 within an elaborate capillary network, not totally 

 free within the ovary, though they are no longer held 

 within a follicle. 



Development of the embryos continues for about 

 a month (Moser 1967a) until they develop pigmented 

 eyes (Gonad Stage 5) and become ready for release. 

 The pigmented eyes are usually black except in S. 

 ruberrimus where they are yellow. Externally the 

 ovary is gray (from the pigmented eyes) and very 

 fragile. It breaks easily when handled and usually 

 some larvae are prematurely extruded when the 

 adult is captured. 



After normal release of the larvae (Gonad Stage 

 6), the ovary consists primarily of an elaborate 

 vascular system, larvae that were not extruded, and 

 a few eggs which failed to develop (atretic oocytes). 

 Externally it appears very mushy and reddish gray, 

 with an opaque and flaccid ovarian wall. 



Resorption and reorganization of the ovary 

 (Gonad Stage 7) occur until vitellogenesis begins 

 (Gonad Stage 3) again. During the months of re- 

 organization (Figs. 1-7) there is evidence of residual 

 larvae, eggs, and capillaries being resorbed, and a 

 proliferation of oogonial nests producing eggs for 

 the next reproductive season. The ovarian wall is 

 between 0.5 and 0.9 mm thick. Externally the ovary 

 is compact and loosely encased by an opaque wall. 

 During resorption the ovary changes from reddish 



brown to grayish brown. When vitellogenesis begins 

 again (Gonad Stage 3) the ovary appears yellow or 

 white. There are usually a few pigmented eyes be- 

 ing resorbed through Gonad Stage 3 from the 

 previous year's brood. 



The principal external characteristic of an imma- 

 ture ovary entering the first reproductive season is 

 the wall, which is thin (0.1 mm) and translucent. 

 There are also no residual pigmented eyes in the 

 ovary. A spent and maturing ovary from a mature 

 fish usually contains remnants of resorbed larvae 

 (evidenced as black dots) encased by a thick, opaque 

 ovarian wall (0.5 to 0.9 mm). 



Developmental Sequence 

 for Testes 



It is often difficult to distinguish an immature 

 from a resting testis in rockfish because the pres- 

 ence of sperm in the testis is not necessarily an in- 

 dication of the fish's maturity. Understanding the 

 developmental sequence of spermatogenesis can 

 help to identify the reproductive stage any time of 

 year (Table 3). 



Histological examination shows that the immature 

 testis (Gonad Stage 1) consists of germ cells, pri- 

 mary spermatogonia, and secondary spermatogonia 

 which lend a whitish color at the periphery. Exter- 

 nally the testis is threadlike and translucent, often 

 with a hint of white from the developing spermato- 

 gonia. 



Spermatogenesis begins at the periphery of the 

 testis and moves centripetally, filling the lumen, the 

 efferent ducts, and finally the sperm duct. A male 

 approaching the first year of maturity (Gonad Stage 



Table 3.— Reproductive development at the cellular and external morphology level 



for testes of Sebastes species. 



Gonad stage 



Cellular morphology 



External morphology 



1. Immature Germ cells, primary and second- 



ary spermatogonia. 



2. First year Spermatozoan cysts throughout 

 maturity testis. No residual sperm in tub- 

 ules or ducts. 



3. Spermato- Large spermatozoan cysts 

 genesis throughout testis with sperma- 

 tozoa in lumen. 



4. Spawning Sperm duct and lumen filled with 



spermatozoa. Spermatogene- 

 sis ceases at periphery. 



6. Recently Abundance of germ cells at 

 spawned periphery. Resorption of sperm 



by tubular boundary cells. 



7. Resting Reorganization of testis. Germ 



cells line spermatogenic tubules. 



Small, threadlike; transparent to 

 white at periphery. 



Small, ribbonlike, and white. No 

 evidence of sperm in central 

 duct (translucent). 



Milky white and swollen, sperm 

 throughout testis in cross sec- 

 tion. 



Large, soft, white; sperm flows 

 freely when cut. Center of testis 

 white, periphery becoming trans- 

 lucent. 



Center is white in cross section, 

 with the periphery becoming 

 firm and darker. 



Firm, compact, and vaguely tri- 

 angular. Color dark gray/brown. 



233 



