NOTE Munehara: Reproductive biology and early life stages of Rodothecus sachi 
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Figure 1 
Retractable genital duct and mature ovary. (A) Genital duct (arrow) and eggs with ovarian 
fluid extracted from the top of the duct. (B) Ovulated eggs in the ovarian cavity and the 
genital duct. 
bony plates followed Gruchy 
(1969) and Maeda and 
Amaoka (1988). 
Resuits 
General anatomy and 
histology of the ovary 
The paired ovary of P. 
sachi was bilobed anteri- 
orly but fused together 
from the middle region; its 
posterior end reached be- 
yond the genital duct, 
which was located at the 
middle of the abdominal 
cavity (Fig 1). The anterior 
part of the genital duct 
was retractable and could 
be everted by pressing the 
fish’s belly. The protruded 
duct was tapered, about 2 
cm length in 27.5-29.1 cm 
standard-length (SL) 
specimens (Fig. 1A). Blood 
vessels in the ovary ran 
radiately in the tunica of 
the dorsal side. The ova- 
rian cavity passed through 
the center of the ovary and 
then directly faced the 
ovarian wall lined with epi- 
thelia near the genital duct. 
The genital pore opened 
just behind the pelvic fins. 
The cavity and the genital 
duct contained several hun- 
dred ripe eggs (Fig. IB). 
Sections of the ovary 
contained oocytes in vari- 
ous developing stages, in- 
cluding the chromatin-nucleolus, perinucleolus, yolk- 
vesicle, oil-droplet, yolk-globule, migratory-nucleus, 
premature, and ripe stages (Fig. 2). In addition, 
postovulatory follicles in the stage just after ovula- 
tion or in the stage of regenerating were also found. 
These observations indicated that female P. sachi 
produce multiple clutches in a breeding season. 
Appearance of eggs 
Eggs were demersal, adhesive, and almost spherical 
in shape. The mean egg size was 1.73 mm in dia- 
meter, ranging from 1.70-1.75 mm (n= 30). The yolk 
was light pink, and many oil droplets and small, 
whitish, granular material were observed within the 
yolk. 
Initiation of egg development 
Although the eggs from the three females were not 
artificially inseminated, most eggs placed in seawa- 
ter had developed to the 2-cell stage after 20 hours 
(Table 1). In contrast, none of the eggs kept in the 
ovarian fluid showed any sign of development. When 
