| Budget Amount *help |
¥17,680,000 (Direct Cost: ¥13,600,000、Indirect Cost: ¥4,080,000)
Fiscal Year 2014: ¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000)
Fiscal Year 2013: ¥6,630,000 (Direct Cost: ¥5,100,000、Indirect Cost: ¥1,530,000)
Fiscal Year 2012: ¥7,410,000 (Direct Cost: ¥5,700,000、Indirect Cost: ¥1,710,000)
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| Outline of Final Research Achievements |
In all gonochoristic vertebrates, the sexual plasticity of the gonads is not retained after the completion of sex differentiation. Here, we studied whether medaka gonads maintain sexual plasticity until adulthood. The depletion of estrogen resulted in a functional female-to-male sex reversal in sexually mature females. The sex-reserved fish showed a typical male pattern of estrogen levels, secondary sex characteristics, and male-like sex behavior. On the other hand, estrogen treatment in adult males undergoing spermatogenesis induced male-to-female sex reversal, producing fertile eggs. In situ hybridization of medaka gonads during female-to-male and male-to-female sex reversals indicated that cysts on the periphery portions of adult gonads are the origins of germ cells and their surrounding somatic cells in the newly formed testicular and ovarian tissues. Gonochoristic fish maintain their sexual plasticity until adulthood and estrogen plays critical roles in maintaing phenotypic sex.
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