Sex differences in the organizational effects of corticosterone in the egg yolk of quail.

Previously, we found that experimentally elevated plasma corticosterone was transferred to egg yolk by female Japanese quail (Coturnix coturnix japonica), and that the chicks hatched from these eggs grew more slowly than controls and had higher responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis as adults. Here, we tested whether exposure to high yolk corticosterone was responsible for the slowed growth and elevated HPA responsiveness by manipulating the steroid content of eggs directly. Eggs were injected prior to incubation with a dose of corticosterone calculated to increase total yolk corticosterone concentration by two standard deviations. We found that elevated yolk corticosterone slowed growth in male but not female chicks and decreased the HPA responsiveness of female but not male adults, in contrast to the results of elevated corticosterone in laying females. Our results are consistent with others that demonstrate sex differences in the organizational effects of glucocorticoids. The mechanisms and adaptive value of such differences have yet to be determined.