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Vol. 50 No. 4, 2011
Development of Gonadal Tissue and Aromatase Function in the
Protogynous Orange-Spotted Grouper Epinephelus
coioides
Ya-Ju
Tsai1, Mong-Fong Lee2, Chia-Yung Chen1,
and Ching-Fong Chang1,3,*
1Department
of Aquaculture, National Taiwan Ocean Univ., Keelung 202, Taiwan
2Department of Aquaculture, National Penghu Univ.,
Penghu 880, Taiwan
3Center of Excellence for Marine Bioenvironment and
Biotechnology, National Taiwan Ocean Univ., Keelung 202, Taiwan
Ya-Ju Tsai, Mong-Fong Lee,
Chia-Yung Chen, and Ching-Fong Chang
(2011) The
protogynous orange-spotted grouper Epinephelus
coioides is a diandric
type of hermaphrodite. We found that a paired gonad developed in a
forked morphology at 1 mo of age, an ovarian cavity within the gonad
was formed at 4 mo of age, and ovarian lamellae containing oogonia and
primary oocytes proliferated at 6.5 mo of age. A single spermatogenic
cyst (SSC) developed at the margin of the ovarian lamella containing
primary oocytes and then various stages of spermatogenic cysts (VSCs)
proliferated within the gonads of primary males. In contrast, an SSC
was present at the margins of the ovarian lamellae containing
vitellogenic oocytes and atretic oocytes of secondary males at 5.4 yr
of age. Positive immunohistochemical expression of proliferating cell
nuclear antigen was detected in nuclei of oogonia, cortical alveoli
oocytes, vitellogenic oocytes, spermatogonia, and spermatocytes, while
perinucleolar oocytes, spermatids, and spermatozoa were negatively
stained. After administration of an aromatase inhibitor (AI) in
juvenile fish for 2 mo, they changed sex into males. Adult fish fed
diets containing the AI for 4 mo also changed sex into males. Abundant
mature spermatogenic cysts became the main components within the
testicular lamellae where single residual primary oocytes were
scattered. Immunohistochemical signals of aromatase were present in
somatic cells around the oogonia, cortical alveoli oocytes,
vitellogenic oocytes, and spermatogenic cysts. The results suggest that
aromatase (estrogen) plays an important role in sex differentiation and
is also involved in sex change in the orange-spotted grouper.
Key words: Aromatase,
Fish, Gonadal differentiation, Male development, Sex change.
*Correspondence: Tel: 886-2-24622192 ext. 5209. Fax:
886-2-24621579. E-mail:B0044@mail.ntou.edu.tw
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