Steroid hormones reverse sex in turtles.

Injection of estradiol benzoate into eggs of snapping turtles and painted turtles caused all embryos to develop as females. A similar but less consistent female-determining effect was associated with injection of testosterone proprionate. Both species of turtles have temperature-dependent sex determination in nature, whereby embryos incubated at cool temperatures (25 degrees) develop as males and embryos incubated at warm temperatures (31 degrees) develop as females. Exogenous estrogens have been shown to feminize embryos in a wide variety of reptiles, although feminization by estrogens as well as testosterone has been demonstrated previously in only one turtle (Pieau, 1974).