Swiss Ornithological Institute, Seerose 1, 6204 Sempach, Switzerland.
Swiss Ornithological Institute, Seerose 1, 6204 Sempach, Switzerland.
Gen Comp Endocrinol. 2020 Feb 1;287:113346. doi: 10.1016/j.ygcen.2019.113346. Epub 2019 Nov 29.
Yolk hormones are substances which transmit non-genetic factors from the mother to the next generation. The systematic changes of yolk hormone concentrations within asynchronously hatching clutches have been interpreted as a means to adaptively shape the offspring's phenotype. However, in synchronously hatching clutches the role of yolk hormones is less understood. We investigated whether seasonal changes between eggs in the yolk hormones testosterone (Testo), progesterone (Prog) and corticosterone (Cort) also occur in the grey partridge, a synchronously hatching precocial species without direct food competition between siblings. Specifically we asked whether yolk hormone concentrations systematically vary with season and whether they affect the offspring's hatching mass, mass gain, circulating baseline and stress-induced Cort. Additionally, we investigated the effect of genetic background and food availability on yolk hormone concentrations by subjecting grey partridge hens of two strains (wild and domesticated) to two different feeding regimes (predictable vs. unpredictable feeding) during egg laying. We hypothesized that egg hormone concentrations change over the season, but breeding in captivity over many generations and ad libitum food access could have resulted in domestication effects which abolished potential seasonal effects. Results showed that progressing season had a strong positive effect on yolk Prog and yolk Testo, but not on yolk Cort. Feeding regimes and strain had no effect on yolk hormones. Offspring mass and mass gain increased and baseline Cort decreased with progressing season. In addition, yolk Testo correlated positively with offspring mass gain and negatively with baseline Cort, while yolk Prog had a positive correlation with baseline Cort. Strain and feeding regimes of the mother had no effect on offspring traits. In conclusion, grey partridge chicks hatching late in the season might benefit from the increased concentrations of the growth-stimulating yolk Testo and by this catch-up in development. Hence, yolk hormone concentration could adaptively shape the offspring phenotype in a precocial species.
卵黄激素是一种从母体传递非遗传因素到下一代的物质。非同步孵化卵中卵黄激素浓度的系统变化被解释为一种适应塑造后代表型的方式。然而，在同步孵化的卵中，卵黄激素的作用还不太清楚。我们研究了在同步孵化的早成性物种灰山鹑中，卵黄中的卵黄激素睾酮（Testo）、孕酮（Prog）和皮质酮（Cort）是否也会随着季节的变化而变化。具体来说，我们想知道卵黄激素浓度是否系统地随季节变化，以及它们是否会影响后代的孵化体重、体重增加、循环基线和应激诱导的 Cort。此外，我们通过让两个品系（野生和家养）的灰山鹑母鸡在产卵期间接受两种不同的饲养制度（可预测和不可预测的饲养），研究了遗传背景和食物供应对卵黄激素浓度的影响。我们假设卵激素浓度会随着季节的变化而变化，但在圈养中经过多代繁殖和自由获取食物可能导致了驯化效应，从而消除了潜在的季节性效应。结果表明，季节的推进对卵黄 Prog 和卵黄 Testo 有强烈的正向影响，但对卵黄 Cort 没有影响。饲养制度和品系对卵黄激素没有影响。随着季节的推进，后代的体重和体重增加增加，基线 Cort 下降。此外，卵黄 Testo 与后代的体重增加呈正相关，与基线 Cort 呈负相关，而卵黄 Prog 与基线 Cort 呈正相关。母亲的品系和饲养制度对后代的特征没有影响。总之，在季节后期孵化的灰山鹑雏鸟可能受益于生长刺激的卵黄 Testo 浓度的增加，并通过这种发育上的追赶。因此，卵黄激素浓度可以在早成性物种中适应性地塑造后代的表型。
