RESEARCH

The undifferentiated gonads of fish, like those of other vertebrates, differentiate into ovaries or testes during ontogenesis. During the course of differentiation, gonads are highly sensitive to steroidal compounds. Exposure to estrogen leads to ovarian differentiation, while exposure to potent androgens causes testicular differentiation. However, after the gonadal differentiation, the bipotentiality of germ and somatic cells are believed to have ceased. Recently, we have shown that estrogen plays critical role for ovarian maintenance in gonochoristic fish. Inhibition of estrogen production via aromatase inhibitor treatments causes oocyte degeneration leading to testicular differentiation, not only at early stages of development, but also at adulthood, indicating that sexual plasticity is labile in fish. Now, our researches are aimed at investigating how estrogen regulates sexual plasticity in fish.

In addition, our interest is also to elucidate the mechanism of natural sex change in tropical marine fishes. We implement various biochemical and molecular biological techniques in vitro and in vivo.

Past research:

• How gonochorisitic fish differentiate into male and female within a critical period.
  

• Estrogen regulates sex change of protogynous hermaprhodite fishes
  

• Estrogen is critical for ovarian maintenance in gonochoristic adults
  

• Tunica Ovary of hermaphrodite fish is a possible site for androgen production
  

• In vitro spermatogenesis in the fish ovary
  

Current research projects

• Mechanism of sex change in the protogynous wrasse and honeycomb grouper.
  

• Mechanism of gonadal sex differentiation in the protandrous anemone fish.
  

• Mechanism of gonadal sex differentiation in the gonochoristic tilapia and golden  rabbitfish.
  

• Effects of endocrine disruptors on sexual function in fish.
  

• The mechanism how endocrine disruptors intercept the reproductive axis in fish.