Data from: Ageing gracefully: physiology but not behaviour changes with age in a diving seabird

A higher proportion of long-lived animals die from senescence than short-lived animals, yet many long-lived homeotherms show few signs of physiological aging in the wild. This may, however, differ in long-lived diving homeotherms that frequently encounter hypoxic conditions and have very high metabolic rates. To examine aging within a long-lived diving homeotherm, we studied resting metabolism and thyroid hormones (N = 43), blood oxygen stores (N = 93), and foraging behaviour (N = 230) of thick-billed murres (Uria lomvia). Because murres dive exceptionally deep for their size and have a very high metabolism, we expected that aging murres would show signs of physiological senescence. We paid particular attention to resting metabolism as we argue that these maintenance costs reflect those experienced during deep dives. Blood oxygen stores (hematocrit), resting metabolic rate and thyroid hormone levels all declined significantly with age in incubating murres 3-30 years of age. In birds measured longitudinally three years apart, thyroid hormone levels and hematocrit were both significantly lower, suggesting progressive changes within individuals rather than selective disappearance of individuals with high metabolic rates. Within our longitudinal dataset, we found no effect of age on dive depth, dive shape, or behavioural aerobic dive limit. A meta-analysis of changes in resting metabolism with age across 15 animal species demonstrated that such declines are pervasive across most of the kingdom. The rate of decline was highest in species with high energy expenditure supporting a linkage between metabolism and senescence. Physiological changes occurred in tandem with advancing age in murres, but offset each other such that there was no detectable decline in behavioural performance.与短寿动物相比，长寿动物因衰老致死的比例更高，但多数长寿恒温动物在野外几乎未表现出生理衰老的迹象。不过，频繁暴露于低氧环境且代谢率极高的长寿潜水型恒温动物，其衰老特征或存在差异。为探究长寿潜水型恒温动物的衰老状况，我们以厚嘴海鸦（Uria lomvia）为研究对象，测定了其静息代谢与甲状腺激素水平（样本量N=43）、血液氧储备（样本量N=93）以及觅食行为特征（样本量N=230）。鉴于厚嘴海鸦按体型而言潜水深度极深且代谢率极高，我们预期衰老的海鸦会表现出生理衰老的迹象。我们重点关注静息代谢指标，因为我们认为这类维持性代谢成本与深潜过程中所需的代谢成本具有一致性。在3至30岁的孵卵期海鸦中，血液氧储备（红细胞比容（hematocrit））、静息代谢率与甲状腺激素水平均随年龄增长出现显著下降。对间隔三年开展重复测量的个体进行分析后发现，其甲状腺激素水平与红细胞比容均显著降低，这表明个体内部存在进行性衰老变化，而非代谢率较高的个体发生了选择性消失。在本研究的纵向数据集内，未发现年龄对潜水深度、潜水形态或行为性有氧潜水极限产生显著影响。一项涵盖15个动物物种的静息代谢随年龄变化的元分析（meta-analysis）显示，这类代谢水平下降现象在动物界绝大多数类群中普遍存在。能量消耗较高的物种其代谢下降速率最快，这为代谢与衰老之间存在关联提供了支持证据。厚嘴海鸦的生理变化随年龄增长同步发生，但这些变化相互抵消，因此未检测到行为表现出现衰退。