Elevated reproduction does not affect telomere dynamics and oxidative stress

Joanna Sudyka, Giulia Casasole, Joanna Rutkowska, Mariusz Cichoń

Oxidative stress and telomere dynamics are considered to be powerful biomarkers quantifying a potential trade-off between current reproduction and self-maintenance. Recent studies confirmed the negative impact of elevated reproduction on telomeres, but the evidence for the cost of reproduction in terms of oxidative stress remains equivocal. In order to induce reproductive costs, we experimentally manipulated reproductive effort by increasing brood size in captive zebra finches (Taeniopygia guttata) and additionally challenged all birds by a low ambient temperature to facilitate detection of these costs. We were not able to show any negative effects of elevated reproductive effort on telomere dynamics and oxidative stress among parents, although brood enlargement was effective in terms of total mass and number of fledged young. Interestingly, irrespective of brood size treatment, we found a significant increase in antioxidant capacity at peak breeding while oxidative damage did not change with time. Our results may suggest that reproduction, instead of generating costs, may stimulate physiological functions promoting self-maintenance in terms of higher protection against free radicals. Possibly, opportunistic breeders such as zebra finches may not impede their future performance for the sake of current reproduction. This study interrogates a molecular background behind one of the most intriguing trade-offs that potentially occurs between self-maintenance and reproduction. We manipulated breeding effort in zebra finches to understand if the cost of reproduction can be mediated by telomere dynamics and oxidative stress. In our study system, we did not detect the direct reproductive costs in terms of parental oxidative damage and telomere loss; instead, these costs were paid by the offspring in terms of their inhibited growth rate. Moreover, we found that entering into the reproductive state strongly stimulated self-maintenance by increasing antioxidant capacity in parents. Our results emphasize that current reproductive success is not always prioritized over investment in body maintenance preventing the oxidative cost of reproduction.