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Fishery Bulletin 103(4) 



Table 1 



Histological criteria used to determine reproductive stage in striped mullet (Mugil cephalus) once sexual differentiation has 

 occurred. Modified from Wenner et al. ( 1986). 



Reproductive stage 



Male 



Female 



1. Immature 



Developing 



3. Running, ripe 



4. Atretic or spent 



5. Inactive or resting 



Inactive testes; small transverse sections 

 compared to those of resting male; sper- 

 matogonia and little or no spermatocyte 

 development. 



Development of cysts containing primary 

 and secondary spermatocytes all the way 

 through accumulation of spermatozoa in 

 lobular lumina and ducts. 



Predominance of spermatozoa in lobules 

 and ducts and little occurrence of sper- 

 matogenesis. 



No spermatogenesis occurring but some 

 residual spermatozoa in shrunken lobules 

 and ducts. 



Larger transverse sections compared to 

 those of immature males; little or no sper- 

 matocyte development; empty lobules with 

 well-developed secondary ductwork and 

 some residual spermatagonia. 



Inactive ovary with previtellogenic oocytes and no 

 evidence of atresia. Oocytes are <80 (ira, lamellae lack 

 muscle, and connective tissue bundles are not as elongate 

 as those in mature ovaries, ovary wall is very thin. 



Developing ovary have enlarged oocytes generally greater 

 than 120 um in size. Cortical alveoli become present and 

 actual vitellogenesis occurs after oocytes reach 180 .um 

 in size and continue to increase in size. Abundant yolk 

 globules with oocytes reach a size range of >600 um. 



Completion of yolk coalescence and hydration in most 

 oocytes. 



More than 30 f ? of developed oocytes undergoing the 

 atretic process. See Table 2 for detailed description of 

 the atretic process. 



Previtellogenic oocytes with only traces of atresia. In 

 comparison to those of immature females, most oocytes 

 are >80 ,«m, lamellae have some muscle and connective 

 tissue bundles; lamellae are larger and more elongated 

 than those of immature females and the ovarian wall 

 is thicker. 



Table 2 



Histological criteria used to determine atretic stage in striped mullet Mugil cephalus). Criteria based on ovarian atretic process 

 described by Hunter and Macewicz (1985) and observational data of striped mullet ovaries from this study. 



Atretic stage 



Description 



1. Alpha atresia a Vitellogenic oocytes are present with distinct yolk globules, which are beginning to break down. The 



most developmentally advanced oocytes will undergo atresia first, followed by less developed oocytes. 

 The oocyte will break down from the interior outward; the vitelline membrane and follicle layers are 

 the last portion of the oocyte to decay. As the oocyte breaks down, a series of vacuoles of various sizes 

 will appear within the oocyte. 



/! The oocytes continue to become reduced in size as they decay. The vacuoles that began to form during 

 the alpha stage are now coalescing together to form one large vacuole within the oocyte. This gives 

 the lamellae a distinct hollow matrix and just the outer layers of the oocyte and follicle are now left. 

 This appears to be the shortest atretic phase. 



7 The oocytes that were left in the hollow matrix during the beta stage now begin to shrink in size and 

 the outer layers fold in on themselves as the oocyte collapses. The areas in and around the collapsed 

 oocytes and lamellae become highly vascularized during this stage in order to facilitate rapid 

 resorption of decaying cellular material. There will still be some vacuoles present within the collapsed 

 oocytes but they have become much smaller and there are far fewer of them. This stage continues 

 until most of the remaining oocytes that developed for spawning are no longer recognizable as oocytes. 



4. Delta atresia A The remnants of old oocytes at this stage are identifiable only as decaying cellular material and 



will stain a distinct yellow-brown color and are still present in (approximately) 30% or more of the 

 material within the ovary. Undeveloped oocytes have a much more distinct and numerous presence 

 within individual lamellae. The amount of vascularization seen in the gamma stage is reduced 

 because most of the old material has been reabsorbed. 



Beta atresia 



3. Gamma atresia 



