Maternally-derived hormones affect offspring physiological and behavioural phenotype, plausibly as an adaptive response to maternal environmental conditions. Corticosterone (CORT), the principal avian glucocorticoid produced in response to stress, is recognised as a potential mediator of such maternal reproductive effects. Maternally-derived yolk CORT is implicated in mediating offspring growth and hatchling begging behaviour. However, determining the potential for maternal effects in opportunistic breeders subject to variable environments relies on understanding whether natural variation in maternal circulating hormones may directly impact the embryo during development. Therefore, we tested whether elevated maternal CORT concentrations increase yolk CORT concentrations in zebra finch (Taeniopygia guttata) eggs. We remotely dosed breeding females with biologically-relevant doses of CORT, or the oil vehicle, 0–3 h prior to the predicted time of ovulation, and allowed pairs to produce two clutches, one under each treatment, in a crosswise, balanced design. CORT dosing elevated maternal plasma CORT and increased mean yolk CORT by a factor of 1.75 compared to the egg yolks of control mothers. Importantly, CORT concentrations did not differ between inner and outer layers of yolk. We found no egg lay order effect and maternal CORT dosing did not influence reproductive outputs (clutch initiation date, clutch size or egg mass). Our results confirm the direct impact of biologically-relevant increases in maternal CORT on yolk CORT, providing evidence that maternal CORT concentrations during yolk deposition to the follicle alters embryonic exogenous CORT exposure. Further research is required to determine the impact of maternal CORT on embryonic developmental programming.

源自母体的激素会影响后代的生理和行为表型，这似乎是对母体环境条件的适应性反应。皮质酮 (CORT) 是应对压力产生的主要鸟类糖皮质激素，被认为是这种母体生殖效应的潜在介质。母体衍生的蛋黄 CORT 与调节后代生长和孵化乞讨行为有关。然而，确定受多变环境影响的机会主义育种者对母体影响的可能性依赖于了解母体循环激素的自然变化是否会在发育过程中直接影响胚胎。因此，我们测试了升高的母体 CORT 浓度是否会增加斑胸草雀 ( Taeniopygia guttata ) 的卵黄 CORT 浓度。） 蛋。我们在预测排卵时间前 0-3 小时，用生物学相关剂量的 CORT 或油载体远程给育种雌性配药，并允许成对产生两个离合器，每个处理一个离合器，在交叉、平衡的设计中。与对照母亲的蛋黄相比，CORT 给药提高了母体血浆 CORT 和平均蛋黄 CORT 的 1.75 倍。重要的是，CORT 浓度在蛋黄内层和外层之间没有差异。我们发现没有产卵顺序效应，母体 CORT 剂量不影响生殖产出（离合器开始日期、离合器大小或卵量）。我们的结果证实了生物相关的母体 CORT 增加对蛋黄 CORT 的直接影响，提供证据表明在卵黄沉积到卵泡期间母体 CORT 浓度会改变胚胎外源性 CORT 暴露。需要进一步的研究来确定母体 CORT 对胚胎发育程序的影响。