Effect of Fromestane on Gonadal Sex Differentiation and Sex Ratio in the Frog, Euphlyctis cyanophlyctis, with Undifferentiated Type of Gonadal Differentiation
There are two patterns of gonad differentiation in amphibians, but the role of sex steroids in gonad differentiation is not clear. I studied the role of estrogen in gonadal sex differentiation in the frog Euphlyctis cyanophlyctis with an undifferentiated type of gonad differentiation (testis differentiates through an ovarian phase) using an aromatase inhibitor, formestane (FR). I treated tadpoles with four concentrations of FR (1, 10, 50, and 100 μg/L) during Gosner stages 25–42. Treatment of higher concentrations (50 and 100 μg/L) of FR produced a male-biased sex ratio and inhibited ovary development but not ovarian cavity and meiocytes formation. These results suggest that estrogen may not be involved in early ovarian differentiation and the ovarian phase is important for testis differentiation in E. cyanophlyctis.Abstract
Transverse sections of gonads in control and formestane (FR)-treated tadpoles of Indian Skipper Frogs, Euphlyctis cyanophlyctis, at Gosner stages 30 and 35. (A) Control gonads at Gosner stage 30. Note the presence of ovarian cavity and meiocytes. (B) Control gonads at Gosner stage 35. Note the growing diplotene oocytes of different sizes surrounded by somatic follicle cells. (C and D) Gonads (at Gosner stage 35) of tadpoles treated with 1 and 10 μg/L FR. Note the growing diplotene oocytes of different sizes and somatic follicle cells. (E and F) Gonads at Gosner stage 35 treated with 50 and 100 μg/L FR. Note the presence of meiocytes and underdeveloped diplotene oocytes. (OC, ovarian cavity; O, oogonium; DO, diplotene oocyte; UO, underdeveloped oocyte; MC, meiocytes; SF, somatic follicle cells).
