EFFECT OF EXOGENOUS ESTRADIOL APPLIED AT DIFFERENT EMBRYONIC STAGES ON SEX DETERMINATION, GROWTH, AND MORTALITY IN THE LEOPARD GECKO (EUBLEPHARIS-MACULARIUS)

Temperature-dependent sex determination (TSD) occurs in three orders o f reptiles. Several studies have examined the ability of estradiol to produce female hatchlings incubated at a male-producing temperature. T he results of these experiments support the idea that estradiol could be used as a powerful tool in the conservation of endangered species w ith TSD by manipulating hatchling sex ratios. However, these experimen ts have concentrated on the mechanism of determination. This experimen t was designed to test the efficacy of various dosages of estradiol ap plied at two different stages to after the hatchling sex ratio as well as determining the potential use of such manipulation for conservatio n efforts by monitoring egg mortality and hatchling growth. The leopar d gecko (Eublepharis macularius) exhibits TSD and reaches reproductive maturity in less than one year, making it an excellent model for eval uating the long-term effects of estradiol. The results demonstrate tha t estradiol has a dose-dependent effect on the hatchling sex ratio whi le only high dosages applied at the later stage of development showed increased mortality. Estrogen-determined females grew at the same rate as temperature-determined females and have produced viable hatchlings . Estradiol treatment of eggs from endangered species may provide a me thod of insuring female offspring when the TSD pattern is unknown or e quipment for controlled incubation is unavailable. (C) 1994 Wiley-Liss ,Inc.