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Fishery Bulletin 99(2) 
the trawl surveys conducted by SNFRI between January 
and February in 1991, 1995, 1996, and 1997, and from the 
commercial trawl fishery in 1991-97. Additional samples 
for February— May were collected in the trawl survey con- 
ducted by Nagasaki University in May 1995. Sexually ma- 
ture individuals collected in September and November- 
January were defined as those larger than the L 50 for that 
sex because most had recrudescent gonads. Between Feb- 
ruary and May, sexually mature individuals were defined 
as males with testes in stage 4 and females with ovaries in 
stages 2 (late), 3, 4, or 5 (see “Results” section). These indi- 
viduals were thought to be pre- or postspawning fish, pos- 
sibly collected at or near the spawning grounds. Sexually 
immature individuals were defined as males with testes in 
stages 1 or 2 and females with ovaries in stage 1. These in- 
dividuals were considered to be nonspawning fishes pres- 
ent during the spawning season. 
Results 
Structure of the testis 
The paired testicular lobes are located in the posterior por- 
tion of the abdominal cavity. The main longitudinal sperm 
duct is located ventral to the testicular groove (hilus) 
in each testis. The seminiferous tubules radiate towards 
and terminate blindly from the testicular periphery of the 
main sperm duct. The germinal cysts of spermatogonia, 
spermatocytes, and young spermatids are arranged ran- 
domly on the walls of the seminiferous tubules (Fig. 2A). 
As young spermatids mature, they are released from their 
cysts into the lumina of the seminiferous tubules (Fig. 
2B). Spermatids and spermatozoa are both found in the 
lumina of the seminiferous tubules and sperm ducts (Fig. 
2, B and C). 
Structure of the ovary 
The right and left ovarian lobes of L. litulon are con- 
nected to each other at their posterior ends, forming a 
single organ. Stalk-like ovigerous lamellae protrude from 
the ovarian wall and each contains many oocytes at dif- 
ferent stages of development. In developing and matur- 
ing ovaries, one or two of the most advanced oocytes are 
located in the terminal portion of each ovigerous lamella, 
and previtellogenic oocytes are found near the base of the 
ovigerous lamella throughout the year. 
The ovarian lumen is lined with both ovarian wall epi- 
thelium and ovigerous lamella epithelium. These epithelia 
undergo morphological changes accompanying the ovar- 
ian maturation cycle (Fig. 3). As ovarian development con- 
tinues in the secondary and tertiary yolk stages, gelati- 
nous material is secreted from both the ovigerous lamellar 
epithelium and ovarian wall epithelium, and fills the ovar- 
ian lumen. 
The early-stage postovulatory follicles are convoluted, 
with many folds, and contain a follicular lumen (Fig. 4A). 
The granulosa cells are either columnar or cuboidal and 
are arranged in a regular manner together with thecal 
A 
sc 
Figure 2 
Photomicrographs of sections of the testis of 
Lophius litulon. (A) Transverse sections of the 
seminiferous tubules during spermatogenesis, 
showing that the germinal cysts are arranged ran- 
domly on the walls of the seminiferous tubules. 
( B ) Transverse sections of the seminiferous tubules 
during spermatogenesis, showing that spermatids 
are released into the lumina of the seminiferous 
tubules. ( C ) Transverse section of the main sperm 
duct during spermatogenesis, showing that both 
spermatids and spermatozoa are present in the 
main sperm duct. Bar = 25 pm; sg = spermatogo- 
nia; sc = spermatocyte; st = spermatid; sz = sper- 
matozoon; de = main duct epithelium. 
cells (Fig. 4B). The nuclei are located in the basal or mid- 
dle portion of the granulosa cells. The late-stage postovu- 
latory follicles are much smaller than those in the previ- 
ous stage, and the follicular lumen continues to decrease 
