Colmenero et al.: Reproductive biology of Lophius budegassa in the northwestern Mediterranean Sea 
395 
also calculated as the number of vitellogenic oocytes 
divided by kilogram of mature female (Murua et al., 
2003). 
Results 
Gonadal morphology 
Ovarian structure consists of a flattened band with 2 
distinctive lobes that are folded up and connected to 
each other at their posterior end. The lobes form a sin- 
gle organ attached to the abdominal cavity by a black 
mesenteric tissue called the mesovarium. One side of 
the ovarian wall is made of an ovigerous membrane 
and connective tissue. The nonovigerous side is made 
of epithelial cells. A single layer of oocyte clusters proj- 
ects from the ovigerous membrane to the lumen (Fig. 
2A). Inside each gonad, the clusters can be in different 
development stages. Only the oocytes situated closest 
to the tip of the clusters have progressed through all 
maturity stages, and the other oocytes are only oogonia 
or in the primary growth stage (Fig. 2B). 
A gelatinous material is secreted into the lumen 
during the late phases of gonad maturation, producing 
the mucus matrix characteristic of the reproduction of 
Lophius species (Fig. 2C). Hydration of the oocytes oc- 
curs just before spawning, and postovulatory follicles 
(Fig. 2D) are found during the regression phase of the 
reproductive cycle. Ripe eggs, which are usually situat- 
ed on the tip of the oocyte cluster, rupture the follicles 
and are pressed into the layer of mucus. In this study, 
every chamber examined contained at least 1 egg in 
the gelatinous matrix (Fig. 2E), although the presence 
of 2 (Fig. 2F) or 3 eggs (Fig. 2G) floating in separate 
chambers was also noted (Fig. 2H). 
Oocyte diameter appeared to differ depending on the 
quantity of oocytes present in each chamber; the oo- 
cytes that were isolated in their chambers were found 
to be larger in size than other oocytes. A diameter of 
486 pm was obtained for the oocyte that was the single 
oocyte in its chamber. Diameters of 427 pm and 359 
pm were found for the 2 oocytes floating together in a 
chamber, and diameters of 341 pm, 330 pm, and 322 
pm were observed for the 3 oocytes that shared the 
same chamber. Measurements of more oocyte diameters 
are needed to confirm these preliminary observations. 
The testes are a pair of elongated and tubular struc- 
tures located in the dorsal portion of the abdominal 
cavity, and they are bean-shaped in transverse section. 
The organization of the testes is lobular: the connec- 
tive tissue extends from the testicular capsule to form 
lobules that have their blind ends on the surface of the 
gonads, converging ventrally towards the sperm duct 
(Fig. 21). These lobules are fused to the posterior end 
of each testicular lobe to form a common sperm duct 
that leads to a genital pore (Fig. 2J). Spermatogenesis 
takes place in a capsule-like sac called a cyst, but it 
is not completed within the cyst. Each cyst contains 
spermatogonia or developing spermatocytes (Fig. 2K). 
Before the end of the spermatogenesis, the cyst breaks 
up and spermatids are released into the lumina of the 
lobules, where spermatogenesis is then completed and 
spermatids transform into spermatozoa (Fig. 2L). The 
cysts appear to be arranged in order of maturation, 
with a gradient of germ cells of increasing maturation 
from the cortex to the sperm duct. The shape of the 
spermatozoa head seems to be elongated. 
Spawning season and size at first maturity 
Monthly distribution of macroscopic classification of 
the maturity phases (Fig. 3, A and B) revealed that the 
period of maximum occurrence of females in the spawn- 
ing capable phase (III) was from November to January. 
The presence of females in the actively spawning phase 
(IV) was observed from November to March, with a 
maximum peak in January. Females in the immature, 
regressing, and developing and regenerating phases (I, 
V, and II, respectively) were found throughout the year, 
with the highest percentage of immature individuals 
seen in May. A slight increase in phase-III females was 
observed in August, and that increase would likely re- 
sult in spawning activity in September, indicating the 
possibility of a secondary breeding season. Males in all 
maturity phases were observed throughout the year, 
with 2 maxima of mature males occurring in Decem- 
ber and July. 
For mature males and females, GSI and HSI indi- 
ces were calculated. In males, GSI was fairly constant 
throughout the year and a maximum index value of 
1.06 was reached in January (Fig. 3C). The mean GSI 
for females was highest from December to March, with 
a peak of maximum activity in January (4.94) and Feb- 
ruary (2.43) (Fig. 3D). The mean HSI for females and 
males followed the same pattern. The highest value for 
males was found in September (2.50), and the lowest 
value in February (1.65) (Fig. 3C). In females, HSI val- 
ues ranged from 3.19 in January to 1.86 in March (Fig. 
3D). The highest HSI values were found just at the 
beginning of the main spawning season. GSI and HSI 
results, together with observations of maturity phases 
throughout the year, indicate that there is one main 
spawning season from November to March. 
Comparison of L 50 curves showed a clear difference 
between males and females. The size at 50% sexual 
maturity was 33.4 cm TL for males (Fig. 4A) and 48.2 
cm TL for females (Fig. 4B). 
Reproductive strategy and fecundity 
The size-frequency distributions of oocyte diameters in 
each of the 5 maturity phases indicate that oocytes in 
different stages of development were found in each ma- 
turity phase (Table 2; Fig. 5). During phase I, only oo- 
cytes in the primary growth stage (chromatin nucleolar 
and perinucleolar) with a narrow range of diameters 
were present (Fig. 5A). In phase II, cortical alveolar 
