Meeting Abstract
The red-eared slider turtle, Trachemys scripta, exhibits temperature-dependent sex determination (TSD), where incubation temperature irreversibly determines the sex of the individual. Previous studies have used exogenous estrogens to successfully sex-reverse individuals incubated under male producing temperatures to examine the pathway and role of estrogens in TSD. It remains unclear, however, if exogenous estrogen is mimicking a natural event in sex determination, or if it is overriding the endogenous sex determination pathway. In the current study, T. scripta eggs were treated with 15µg of 17-β estradiol in 5µl 100% EtOH under two dosing schedules during the temperature sensitive period (TSP) of development at both male- (26 °C) and female- (30 °C) producing temperatures. Eggs were allowed to incubate until embryonic stage 26 and were subsequently dissected and the gross morphology of the gonads were examined, sexed when possible, and compared across treatments. The sex and presence of the gonad were verified through histology of the adrenal-kidney-gonad complex. In a few cases, eggs treated with 17-β estradiol exhibited ovary-like gonads that were reduced in size compared to the control. However, in the majority of cases, the treatment of eggs with 17-β estradiol resulted in the absence of the gonad, and thus appeared to block normal gonadal differentiation. Collectively, these results indicate that relatively large doses of exogenous estrogens applied at the beginning of the TSP may disrupt the normal process of gonadal differentiation, and may be altering the natural sex-determination pathway instead of mimicking the native pathway. These findings provide an avenue for investigating the temporal and functional aspects of estrogen sensitive components in the sex determination cascade.
