The Relative Effectiveness of Androstenedione, Testosterone, and Estrone, Precursors to Estradiol, in Sex Reversal in the Red-Eared Slider (Trachemys scripta), a Turtle with Temperature-Dependent Sex Determination

In many turtles the temperature during the middle of incubation determines the gonadal sex of the hatchling. Sex steroid hormones have been implicated in temperature-dependent sex determination in the red-eared slider turtle, Trachemys scripta ; androgen is involved in male sex determination and estradiol in female sex determination. Administration of exogenous estradiol and its agonists to eggs incubating at a male-producing temperature can overcome the effect of temperature and result in all-female offspring. Exogenous testosterone will also result in some female hatchlings if administered to eggs incubated at a male-producing temperature, an effect due to the aromatization of testosterone to estradiol. This study demonstrates that in the red-eared slider, androstenedione, the precursor to both testosterone and estradiol, has a similar effect. In addition, both testosterone and androstenedione synergize with incubation temperature to exert a greater effect at intermediate incubation temperatures that normally produce mixed sex ratios, indicating that as with estradiol, androstenedione and testosterone are involved in the final common pathway of sex determination in this species. At the single dosage administered, estrone and estradiol produced all females at a male-producing incubation temperature.