Oxidative status and telomere length in a long-lived bird facing a costly reproductive event
Résumé
Life-history theory predicts that high reproductive investment alters self-maintenance. Several mechanisms underlying the cost of reproduction have been previously suggested, but how parental effort may impact cell and organism maintenance remains largely unknown. The effects of oxidative stress - the unbalance between oxidative damage and defences - on telomere dynamics may underlie this relationship. Indeed, oxidative stress is associated to costly activities like breeding and impacts telomere length that is known to predict survival in birds. According to life-history theory, long-lived species are expected to minimize the adverse effects of current reproduction on their body maintenance and should therefore control their oxidative stress and preserve their telomeres whatever the breeding workload. In the present paper, we tested this hypothesis by determining experimentally how the oxidative balance and telomere length are modified when long-lived Adélie penguins (Pygoscelis adeliae) face a costly reproductive event. In agreement with the hypothesis postulating that long-lived species should prioritize their self-maintenance, Adélie penguins substantially increase their antioxidant defence when experiencing a costly breeding effort. This antioxidant adaptability was associated with no acceleration in the change of telomere length reflecting no impact on organism senescence. While previous studies have shown that long-lived species favour self-maintenance when breeding constraints increase, our study is the first to point a cellular mechanism likely to explain how this may occur, thereby confirming experimentally that the couple oxidative stress / telomere is an essential mediator of life-history strategies.