650 



Fishery Bulletin 102(4) 



Table 1 



Characteristics of each macroscopic stage in the development of the ovaries of Rhabdosargus sarba, and its corresponding histo- 

 logical characteristics. Adapted from Laevastu (19651. Terminology for oocyte stages follows Wallace and Selman (1989). 



Stage 



Macroscopic characteristics 



Histological characteristics 



I Virgin 



Ovary is very small and strand-like. 



II Immature 



and resting 



Small and transparent. Yellowish-orange in 

 color. Oocytes not visible through ovarian 

 wall. 



Ill Developing Slightly larger than stage II. Reddish color. 

 Oocytes visible through ovarian wall. 



Rhabdosargus sarba is a rudimentary hermaphrodite, sensu 

 Hesp and Potter (2003). Thus, the gonads of small juveniles 

 contain only connective tissue. Larger juveniles possess 

 gonads (ovotestes) in which each ovarian lobe consists of 

 an immature ovarian and testicular zone, separated by 

 connective tissue. The ovotestes develop later into gonads 

 containing almost entirely ovarian tissue (functional ovaries) 

 or, in the case of males, gonads containing almost entirely 

 testicular tissue (functional testes). 



Ovigerous lamellae highly organized. Chromatin nucleolar 

 and perinucleolar oocytes dominate the complement of 

 oocytes. Oogonia sometimes present. Chromatin nucleolar 

 oocytes present in all subsequent ovarian stages. 



Chromatin nucleolar, perinucleolar and cortical alveolar 

 oocytes present. 



Cortical alveolar and yolk granule oocytes abundant. 



IV Maturing Larger than stage III. Reddish-orange in 



color. Yolk granule oocytes visible through 

 ovarian wall. 



V Mature Larger than stage IV occupying half to two Yolk granule oocytes predominant. 



thirds of body cavity. Extensive capillaries 

 visible in ovarian wall. 



VI Spawning Hydrated oocytes visible through ovarian Migratory nucleus oocytes, hydrated oocytes, or postovula- 



wall. Note that fish with ovaries in "spawn- tory follicles present, 

 ing condition" can only be detected macro- 

 scopically when caught during the hydration 

 period. 



VII Spent 



Smaller than V and VI and flaccid. Some yolk Some remnant yolk granule oocytes present, all or almost al 

 granule oocytes visible through ovarian wall. of which are typically undergoing atresia. 



VIII Spent and Small and dark red. 

 recovering 



Extensive scar tissue present. Ovarian lamellae becoming 

 reorganized. No yolk granule oocytes present. 



females with stage-V (mature) or stage-VI (spawning) 

 ovaries (see Table 1 for definitions of these stages). 



During the above sampling, R. sarba was collected 

 for up to 2 hours at intervals commencing at 18:30, 

 21:30, 00:30, and 03:30 h on 1-2 September 2001 and 

 for up to 2 hours at intervals commencing at 18:30 and 

 22:30 h on 13 September 2001. One of the ovarian lobes 

 of up to five fish caught during each of these above 

 time intervals was cut into several pieces, preserved in 

 10'' neutrally buffered formalin solution and used for 

 determining the distributions of oocyte diameters at 

 the above different times. The other lobe was used for 

 histology to determine the oocyte stages present in that 

 lobe, and thus, by extrapolation, also the stages of the 

 oocytes in the lobe that had been preserved in formalin. 

 The resultant comparisons were used, in conjunction 

 with data from other times, to elucidate the pattern of 



oocyte development during hydration and the duration 

 of hydration and timing of ovulation. 



Gonadal staging and histology of ovaries 



The sex, total length (to the nearest 1 mm), and total 

 weight and gonad weight (to the nearest 0.01 g) of each 

 fish were recorded. From its macroscopic appearance, 

 each gonad was assigned to one of the following stages in 

 maturation, based on the scheme of Laevastu (1965), i.e., 

 I = virgin, II = immature and resting, III = developing, 

 IV = maturing, V = mature, VI = spawning, VII = spent, 

 VIII = spent and recovering. The corresponding histolog- 

 ical characteristics of each macroscopic stage are shown 

 in Table 1. When hydrated oocytes could be seen through 

 the ovarian wall of a fish, a note was made as to whether 

 they were distributed throughout the ovary or were in 



