Saino Nicola, Romano Maria, Ferrari Raffaella Paola, Martinelli Roberta, Møller Anders Pape
Dipartimento di Biologia, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
J Exp Zool A Comp Exp Biol. 2005 Nov 1;303(11):998-1006. doi: 10.1002/jez.a.224.
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.
生物体经常会遇到压力重重的生态环境。在脊椎动物中，对压力的主要生理反应机制由下丘脑 - 垂体 - 肾上腺轴介导，会导致糖皮质激素分泌增加，这可能会对影响适应性的各种表型特征产生不利影响。因此，如果母体压力在糖皮质激素浓度方面影响产前子代环境，那么它可能会对子代产生延续效应，尽管这一假设从未在野外条件下的任何物种中得到验证。我们通过在雌性家燕（Hirundo rustica）产卵期间将它们暴露于捕食者面前来操纵它们所经历的压力，并测量了卵中的皮质酮浓度。与暴露于食草动物的对照组相比，受到压力的雌性所产的卵皮质酮浓度更高。在另一项实验中，我们在蛋清中注射生理剂量的皮质酮，并将这些卵孵化出的子代的表型与其来自假接种或未处理的卵并在同一巢中饲养的对照兄弟姐妹进行比较。注射了皮质酮的卵孵化率较低，孵出的雏鸟体型较小，羽毛发育较慢，而对照卵则不然。我们研究种群中的雏鸟体型可预测其长期生存情况。因此，母体压力通过增加糖皮质激素向卵中的传递，损害了子代的表型和生存能力。这项研究确定了一种介导早期母体效应的新机制，即母体压力影响子代质量。这些结果与生物保护相关，因为它们揭示了一种可将环境条件与种群生产力和生存能力联系起来的机制。
