Stressed mothers lay eggs with high corticosterone levels which produce low‐quality offspring

Abstract

Organisms frequently encounter stressful ecological conditions. In vertebrates, a major mechanism of physiological response to stress is mediated by the hypothalamic-pituitary-adrenal axis and results in increased secretion of glucocorticosteroids, which can have adverse consequences on diverse phenotypic traits affecting fitness. Maternal stress may thus have carry-over effects on progeny if it influences pre-natal offspring environment in terms of glucocorticosteroid concentration, although this hypothesis has never been tested in any species under field conditions. We manipulated stress experienced by female barn swallows Hirundo rustica, by exposing them to a predator during laying and measured egg corticosterone concentration. Stressed females laid eggs with greater corticosterone concentration than controls exposed to a herbivore. In another experiment, we injected physiological doses of corticosterone in the egg albumen and compared the phenotype of offspring originating from these eggs with their control siblings originating from either sham-inoculated or unmanipulated eggs and reared in the same nest. Eggs injected with corticosterone had lower hatchability and produced fledglings with smaller body size and slower plumage development than did control eggs. Nestling body size in our study population predicts long-term survival. Thus, maternal stress impaired offspring phenotype and viability by increasing transmission of glucocorticosteroids to the eggs. This study identifies a novel mechanism mediating early maternal effects whereby maternal stress affects offspring quality. These results are relevant to biological conservation because they disclose a mechanism that can link environmental conditions to population productivity and viability.

Hormone-mediated maternal effects in birds:mechanismsmatter but what do we know of them?

“…Studies with house sparrows treated with testosterone in the egg indicate an enhanced corticosterone stress response of adult females but not males, suggesting sex-specific effects on the HPA axis that carry over into adulthood (Partecke & Schwabl in preparation). Conversely, stressed mothers lay eggs with high yolk corticosterone concentrations (Hayward & Wingfield 2004;Saino et al 2005) and exposure to corticosterone in the yolk enhances HPA function in Japanese quail (Hayward & Wingfield 2003).…”

Hormonally mediated maternal effects, individual strategy and global change

“…In contrast, maternal stress induced lower hatching success and reduced growth rate of barn swallow chicks, leading to smaller size at fledging. Because body size at independence is associated with survival, Saino et al [165] suggest that lower offspring quality may have a large influence on population dynamics. The pattern of reduced embryo body mass and higher mortality with an increase in maternal corticosterone levels was also observed in domestic species [166].…”

An experimental analysis of the heritability of variation in glucocorticoid concentrations in a wild avian population

“…In mammals, prenatal CORT exposure and postnatal maternal care (such as grooming and time spent with offspring) can induce long-lasting changes in offspring HPA responsiveness mediated through epigenetic processes [31,55,56]. In avian species, variation in the amount of CORT deposited in egg yolks may have similar effects on offspring phenotype [57][58][59]. Nest environment prior to hatching such as incubation temperature can also alter nestling baseline and stress-induced CORT levels [60].…”