GREELEY ET AL.: STRIPED MULLET OVARY 



by Wallace and Selman (1981); oocytes 0.18 mm in 

 diameter and larger are considered to be actively 

 vitellogenic. 



Late vitellogenic oocytes become competent to 

 resume meiotic maturation and develop into a fer- 

 tilizable egg in response to an in vitro steroid chal- 

 lenge at 0.60 mm in diameter, with larger oocytes 

 being only marginally more responsive (Table 1). 

 Therefore, oocytes 0.60 mm and larger that do not 

 exhibit any signs of maturation such as yolk "clear- 

 ing" or hydration are considered to be in a pre- 

 maturation stage of development. 



Striped mullet eggs following meiotic maturation 

 are even larger (0.90 to 1.00 mm in diameter) (Abra- 

 ham et al. 1966; Nash et al. 1973; Pien and Liao 

 1975; Finucane et al. 1978; Greeley et al. 1986b), 

 nearly transparent (yolk has cleared), hydrated, float 

 in full-strength seawater, and thus are easily distin- 

 guished from the smaller and more opaque pre- 

 maturation oocytes. Females with matui'e eggs were 

 not collected during this study. 



Table 1 .—Percentage of different-sized striped 

 mullet oocytes undergoing germinal vesicle 

 breakdown (GVBD) in vitro in response to treat- 

 ment withi 17a-fiydroxy-20/3-difiydroproges- 

 terone (1 ^ig/mL) or an ethanol control. 



Largest Oocyte Diameter (LOD) 



The relationship of oocyte diameter to stages of 

 oocyte development is clearly delineated in Figure 

 3. Three major developmental stages are shown: 

 1) previtellogenic growth, including both the pri- 



° 1984-1985 

 • 1985-1986 



oo • 



4 



• o 



i 



• 

 o 

 o 

 o o 



I 



I 



o 8 



i 



Mature or 

 Maturing Oocytes 



Prematuration 

 Oocytes 



Vitellogenic 

 Oocytes 



Figure 3.— Variation in the largest oocyte diameter (LOD) of female Mugit cephalus >20 cm SL during prespawning ovarian 

 recrudescence along the northeast Florida coast. Presented on the right are oocyte developmental stages corresponding to 

 these oocyte sizes. Broken line between vitellogenic and prematuration designations signifies uncertainty concerning whether 

 the latter is actually a substage of the former. The category "previtellogenic" encompasses both primary growth and yolk 

 vesicle oocytes. 



191 



