Sensitive periods during embryogeny for hormonally induced sex determination in turtles

Administration of exogenous estradiol between embryonic stages 10 and 19 inclusive caused embryos of snapping turtles (a species which exhibits temperature-dependent sex determination) to develop ovaries rather than testes, while administration of hormone either prior to stage 10 or after stage 22 did not affect the predicted sex ratio of offspring. Thus the sensitive period for hormonal effects on gonadal development apparently coincides with the period of normal gonadal differentiation. In light of these and prior results use of the term "sex reversal" when discussing the effects of hormones on gonadal differentiation may be a misnomer. We suggest the alternative phrase "hormonally induced gonadal differentiation" (HGD) as a substitute. Results also indicate that variations in the timing of injections among studies may account for at least some of the interspecific differences previously reported for effects of exogenous hormones on gonad differentiation.