Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia.
Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia.
Gen Comp Endocrinol. 2021 Nov 1;313:113898. doi: 10.1016/j.ygcen.2021.113898. Epub 2021 Sep 4.
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.
母体来源的激素会影响后代的生理和行为表现，这可能是母体环境条件的一种适应性反应。皮质酮（CORT）是鸟类对压力产生的主要糖皮质激素，被认为是这种母体生殖效应的潜在介质。母体来源的卵黄皮质酮被认为介导了后代的生长和雏鸟乞食行为。然而，确定在环境多变的机会主义繁殖者中母体效应的潜力，依赖于了解母体循环激素的自然变异是否会直接影响胚胎发育。因此，我们测试了在预测排卵时间前 0-3 小时，用生物相关剂量的皮质酮或油载体远程给繁殖雌性注射是否会增加斑胸草雀（Taeniopygia guttata）卵中的卵黄皮质酮浓度。我们允许配对在交叉平衡设计下，在每种处理下各产两窝卵，以此来进行测试。皮质酮注射使母体血浆皮质酮水平升高，并使平均卵黄皮质酮水平比对照母亲的卵黄高出 1.75 倍。重要的是，卵黄的内外层之间皮质酮浓度没有差异。我们没有发现产卵顺序的影响，而且母体皮质酮注射也没有影响繁殖产出（产卵日期、产卵量或卵质量）。我们的结果证实了母体皮质酮的直接作用对卵黄皮质酮的影响，这表明在卵黄沉积到滤泡期间母体皮质酮浓度的变化会改变胚胎外源性皮质酮的暴露。需要进一步研究来确定母体皮质酮对胚胎发育编程的影响。
