DODD, K.L.**; WIBBELS, T.; Univ. of Alabama, Birmingham; Univ. of Alabama, Birmingham: Clutch-specific Sensitivity to Estrogen in a Turtle with Temperature-dependent Sex Determination

Most turtles exhibit temperature-dependent sex determination in which the incubation temperature of the egg determines the sex of the embryo. Previous studies have revealed clutch-specific variation in the pivotal temperature of sex determination in the red-eared slider turtle. For example, experiments in our laboratory indicate that clutch sex ratio can vary from all male to all female at near-pivotal temperatures. In the current study, we investigate whether this clutch-specific variation also extends to steroid hormone sensitivity. Many previous studies have shown that application of estrogen to eggs incubated at male-producing temperatures will cause sex reversal of the embryos. In the current study, eighteen clutches were incubated at male-producing temperature. These eggs were treated with a relatively low dosage of estrogen during the thermosensitive period. For a control, a separate group of eggs were incubated at male-producing temperature and treated with an ethanol solution. The control group of eggs produced all males. The sex ratios of the estrogen-treated clutches varied significantly and ranged from all male to all female clutches. The results indicate a clutch-specific sensitivity to estrogen. Thus, temperature-dependent sex determination in the red-eared slider turtle shows clutch-specific sensitivity to both temperature and exogenous estrogen.