The effect of corticosterone near meiotic segregation on offspring primary sex ratio in zebra finches (Taeniopygia guttata)
Gam, Ashley E.
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Chronic elevations of corticosterone have been shown to stimulate female-biased sex ratios in several avian species. Since female birds are the heterogametic sex, skews may occur prior to ovulation through non-random segregation of sex chromosomes at meiosis I. We tested the hypothesis that corticosterone can influence offspring sex ratios immediately before meiosis I completes. In zebra finches, we examined the effects of acute pharmacological and physiological corticosterone elevations near meiotic segregation on primary offspring sex ratios, as well as the relationship between natural baseline levels of corticosterone around the time of meiotic segregation and sex ratios. Females injected with pharmacological levels of corticosterone produced significantly more males. Endogenous elevations of corticosterone, both stress induced and basal levels did not influence sex ratio. These results suggest that a pharmacological dose is needed for corticosterone to induce a skew near meiosis I and that physiological corticosterone may need to be experienced chronically to induce a skew.