Hesp et al : Age and size composition, growth rate, reproductive biology, and habitats of Glaucosoma hebmicum 



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Table 1 



Characteristics of the macroscopic stages in the development ofthe gonads of Glai/cuKDiua lichmiciini and, in the case of the ova- 

 ries, the histological characteristics of each corresponding ovarian stage. Terminology for oocyte stages follows Khoo ( 1979). 



Stage 



Macroscopic appearance 



Histological characteristics 



l-ll (virgin 

 and immature) 



III (developing) 



rV (maturing) 



V (prespawning) 



VI (spawning) 



VII (spent) 



VIII 



(.recovering spent) 



Gonads very small. Ovaries transparent and oocytes 

 not visible. Testes strandlike and gray-white. 



Gonads slightly larger than at stage I or II. Ovaries 

 pinkish, blood capillaries visible in ovary walls. 

 Testes white and more lobular. 



Gonads markedly larger. Ovaries reddish-orange, 

 capillaries more conspicuous and some yolk granule 

 oocytes visible through ovary wall. Milt is not 

 extruded when pressure is applied to testes. 



Ovaries orange and occupy most of space in body 

 cavity. Extensive capillaries in ovary walls. Milt 

 appears when testes placed under firm pressure. 



Same as for stage V, but with hydrated oocytes 

 visible through ovarian wall and only slight pressure 

 required to release milt from testes. 



Gonads smaller than at stages V or VI. Ovaries 

 flaccid. Some yolk granule oocytes still visible 

 through ovary wall. Testes pinkish-red. 



Gonads greatly reduced in size and dark red. Testes 

 strandlike. 



Ovigerous lamellae highly organized. Oogonia and 

 chromatin nucleolar oocytes and, in more advanced 

 ovaries, early perinucleolar oocytes are present. 

 These oocyte stages are present in all subsequent 

 ovarian stages. 



Early and late perinucleolar oocytes and yolk vesicle 

 oocytes present. 



Yolk vesicle and yolk granule oocytes abundant. 



Yolk granule oocytes abundant and in tight groups. 



Hydrated oocytes or postovulatory follicles (or both) 

 present. 



Remnant yolk granule oocytes present, typically under- 

 going atresia. 



Lamellae not organized as in early stages of develop- 

 ment and contain extensive scar tissue. Any remain- 

 ing yolk gi'anule oocytes are atretic. 



(maturing) and stages V and VI (prespawning and spawn- 

 ing) were first recorded in September and October, respec- 

 tively. Stage-V and stage-VI ovaries collectively became the 

 most prevalent group in females in November and formed 

 the most dominant group by far in December to March. 

 The samples in February and March contained a few fe- 

 male fish with stage I-II ovaries, but none with ovaries at 

 either stage III or FV (Fig. 6). These trends provide over- 

 whelming circumstantial evidence that any female whose 

 ovaries have developed to at least stage III by November 

 will progress through to maturity during the following 

 months of the spawning period. Thus, the L^,, for females 

 at first maturity was calculated by using the percentage of 

 ovaries with stages III and FV, as well as those with stages 

 V-VIII. Although females with stage-VII (spent) and stage- 

 VIII (recovering spent) ovaries were found between Janu- 

 ary and May, the majority of ovaries were at stages I-II in 

 the latter month and all were at stages I-II in June. The 

 trends exhibited by the pattern of gonadal development in 

 males were essentially the same as those just described for 

 females and thus the L-q of males was likewise calculated 

 with the percentage of testes at stages III- VIII (Fig. 7). 



The following account of the trends exhibited by the oo- 

 cyte composition of ovaries is based on an histological ex- 

 amination of the ovaries of large fish well above the L^g 

 at first maturity. The oocytes in ovaries in July and Au- 

 gust were almost exclusively at the chromatin nucleolar 

 stage. Ovaries with yolk vesicles first appeared in Septem- 

 ber, and those with yolk granules were first found in Oc- 

 tober. Yolk granule oocytes became increasingly prevalent 

 in ovaries in November and dominated the complement of 

 their larger oocytes between December and March. Some 

 of the residual yolk granule oocytes in April and all of 

 those in May were undergoing atresia. No yolk vesicle or 

 yolk granule oocj^tes were found in June. Hydrated oocytes 

 were first found in ovaries in November and were present 

 in many ovaries between December and March and in a 

 few ovaries in April, but were found neither in May nor in 

 the immediately ensuing months. Small numbers of post- 

 ovulatory follicles were present in about a third of the 

 ovaries of large females caught between December and 

 March. The oocyte diameters of individual large G. hebra- 

 iciim caught in each month of the spawning period pro- 

 duced a series of modes (data not shown). 



