Data from: Ageing and reproduction: antioxidant supplementation alleviates telomere loss in wild birds

Reproduction is inherently costly. Environmental stressors, such as infection and limited food resources, can compromise investment at each breeding attempt. For example, recent data on captive birds showed that increased reproductive effort accelerates ageing. However, the effects of nutritional status and infection on ageing remain unknown. Telomeres function as protective caps at the ends of eukaryotic chromosomes, and changes in telomere length is a commonly used proxy for ageing. To partially address the mechanisms of ageing following reproduction, we supplemented, medicated or administered a combined treatment to wild blue tits (Cyanistes caeruleus) breeding in central Spain during 2012. The nutritional supplement consisted of two different antioxidants, while the medication was an antimalarial treatment against blood parasites. We evaluated the effect of these manipulations on reproductive success and parasite loads in the first breeding season, and on changes in telomere length between two consecutive breeding seasons. Supplemented birds showed no reduction in blood parasite infections in 2012, although they exhibited higher body mass and fledging success. The antimalarial drugs reduced infections by several parasite species, but this had no effect on fitness parameters. In the following season, telomeres from supplemented birds had shortened less. Altogether, we found that supplementation with antioxidants provided fitness benefits in the short term and reduced telomere loss a year following treatment. Our results provide indirect empirical support for accelerated telomere loss as a cost of reproduction.繁殖本身即伴随高昂代价。环境胁迫因子（如感染与食物资源匮乏）会削弱每次繁殖尝试中的资源投入。例如，近期针对圈养鸟类的研究数据显示，繁殖投入的增加会加速衰老进程。然而，营养状态与感染对衰老的影响仍未明确。端粒（telomeres）是真核生物染色体末端的保护性帽状结构，端粒长度的变化是目前常用的衰老替代标志物。为部分阐明繁殖后衰老的潜在机制，我们于2012年对在西班牙中部繁殖的野生蓝山雀（Cyanistes caeruleus）开展了营养补充、药物干预或联合处理实验。本次实验的营养补充剂包含两种不同的抗氧化剂，而药物则为针对血液寄生虫的抗疟治疗方案。我们评估了这些干预手段在首个繁殖季对繁殖成功率与寄生虫负荷的影响，以及连续两个繁殖季之间端粒长度的变化情况。2012年，接受营养补充的个体血液寄生虫感染率未出现下降，但其体重与雏鸟离巢成功率均更高。抗疟药物可降低多种寄生虫的感染负荷，但这并未对适合度参数产生显著影响。在次年的繁殖季中，接受营养补充的个体端粒缩短幅度更小。综合来看，我们发现抗氧化剂营养补充可在短期内提升个体适合度，并在处理一年后减缓端粒损耗。本研究结果为“端粒加速损耗是繁殖代价之一”这一假说提供了间接的实验证据。