117.5 Saturday, Jan. 7 Effects of acute, physiological elevations of corticosterone on offspring sex ratios in two avian species PINSON, SE*; GAM, AE; NAVARA, KJ; University of Georgia, Athens; University of Georgia, Athens; University of Georgia, Athens email@example.com
Birds have demonstrated a remarkable ability to bias offspring sex. Studies suggest that female birds may use hormones to mediate skews in offspring sex ratios. Corticosterone, the primary stress hormone in birds, is of particular interest as a potential mediator of offspring sex because it regulates responses to environmental and social stimuli that trigger sex ratio biases and it is elevated during and participates in ovulation in birds. In previous studies, elevation of corticosterone concentrations for long periods of time stimulated female-biased sex ratios while acute elevations in the pharmacological range stimulated male-biased sex ratios. Here, we aimed to test the effects of short-term physiological elevations of corticosterone during chromosome segregation on offspring sex ratios. Based on the results of other studies involving acute corticosterone treatment, we hypothesized that females with acute, physiological elevations of corticosterone would produce more male offspring. We tested our hypotheses in two avian species -- zebra finches and laying hens. First, we administered a handling stress to zebra finches five hours prior to chromosome segregation and quantified sexes of the resulting embryos. Because laying hens often show dampened responses to handling, we instead elevated corticosterone in the physiological range using injections of corticosterone prior to chromosome segregation. Contrary to our hypothesis, neither zebra finches nor laying hens produced sex ratios that differed significantly from controls or hypothetical 50:50 ratios. Results of this study suggest that elevation of corticosterone concentrations within the physiological range for just a few hours prior to ovulation is not sufficient to bias sex ratios in birds.