Sex change of adult initial-phase male wrasse, Halichoeres trimaculatus by estradiol-17 beta treatment.
Sex steroids are considered major regulators of sex change processes in fish. Estrogen depletion is shown to be crucial for female-male sex change initiation; however, its role in male-female sex change is largely unknown. In the present study, we examined the effects of estradiol-17 beta (E2) treatments on testes of initial-phase (IP) males of the three-spot wrasse (Halichoeres trimaculatus), which naturally do not undergo male-female sex change. Sexually mature IP males were fed a diet containing E2 (low, 20 microg/g feed; high, 200 microg/g feed) for 6 or 12 weeks, and changes in gonadal structures were examined. Percentage of sex change varied with the dosage of E2 and the duration of treatment. All individuals treated with high-dose E2 for 6 weeks had ovaries with many immature oocytes; whereas 75% of individuals treated with low-dose of E2 for 6 weeks and sampled on the 12th week had ovaries with yolky oocytes and an ovarian cavity indicating a typical mature ovary. No testicular tissue was observed in sex-reversed gonads in both treatment groups. Contrary to the previous assumptions, present results suggest that IP male wrasses have the potential to undergo male-female sex change in response to exogenous estrogen. How the presence or absence of estrogen creates sexual plasticity in gonadal germ and somatic cells remains to be clarified.
Kojima
Y
Y
Tropical Biosphere Research Center, Sesoko Station, University of the Ryukyus, Sesoko 3422, Motobu, Okinawa 907-0227, Japan.
Bhandari
R K
RK
Kobayashi
Y
Y
Nakamura
M
M
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005262:Feminization; D005854:Germ Cells / Q000187:drug effects; D006107:Granulosa Cells / Q000187:drug effects; D008297:Male; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects; D010053:Ovary / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects; D010473:Perciformes / Q000502:physiology*; D012733:Sex Differentiation / Q000187:drug effects*; D013091:Spermatogenesis / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects; D013737:Testis / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects
D004958:Estradiol