Data from: Telomere length reflects reproductive effort indicated by corticosterone levels in a long-lived seabird

Telomere length (TL) is a candidate biomarker of ageing and phenotypic quality, but little is known of the (physiological) causes of TL variation. We previously showed that individual common terns Sterna hirundo with high reproductive success had short telomeres independent of age, and this pattern was particularly strong in the longer telomeres of the within-individual TL distribution. To test whether this relation can be attributed to effects of reproductive effort, we investigated baseline corticosterone in relation to reproductive success (number of fledglings) and TL. In this context, we assume that variation in baseline corticosterone can be interpreted as index of energy expenditure and allostatic load. Males with higher corticosterone levels during incubation, compared between and within individuals, achieved higher reproductive success and had shorter telomeres. The effect on telomeres was more pronounced in corticosterone measured later in incubation and in the longer telomeres of the within-individual TL distribution. Female corticosterone level during incubation was neither related to reproductive success nor to TL. That we observed these effects only in males mirrors different parental roles during reproduction in the common tern, where males do most of the chick provisioning. The negative association between reproductive success and TL suggests individual differences in reproductive effort as reflected in, or mediated by, baseline corticosterone. We see this result as a promising step towards unravelling the physiological causes of variation in TL and the costs of reproduction.

端粒长度（Telomere length, TL）是衰老与表型质量的候选生物标志物，但目前学界对端粒长度变异的生理成因仍知之甚少。我们此前曾发现，繁殖成功率较高的普通燕鸥（Sterna hirundo）个体端粒更短，且这一规律不受年龄影响，尤其在个体内端粒长度分布的较长端区间中表现得更为显著。为验证这一关联是否可归因于繁殖投入的影响，我们探讨了基础皮质酮（corticosterone）与繁殖成功率（离巢幼鸟数量）及端粒长度之间的关系。在此研究框架下，我们假设基础皮质酮水平的变异可作为能量消耗与异生负荷（allostatic load）的指标。在个体间及个体内的比较中显示，孵卵期间皮质酮水平更高的雄性个体繁殖成功率更高，端粒长度更短。且该端粒长度相关效应在孵卵后期测定的皮质酮样本，以及个体内端粒长度分布的较长端区间中表现得更为显著。雌性燕鸥在孵卵期间的皮质酮水平，既与繁殖成功率无关，也与端粒长度无关联。仅在雄性个体中观察到上述效应，这反映了普通燕鸥繁殖过程中的双亲角色差异——雄性负责大部分幼鸟育雏工作。繁殖成功率与端粒长度之间的负相关关系表明，繁殖投入的个体差异可通过基础皮质酮反映或介导。我们认为该研究结果为阐明端粒长度变异的生理成因及繁殖成本提供了富有前景的研究路径。