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Oxidative stress affects sperm performance and ejaculate redox status in subordinate house sparrows

Alfonso Luis Rojas Mora, Alexandra Firth, Sophie Blareau, Armelle Vallat & Fabrice Helfenstein

Résumé Oxidative stress (OS) is the result of random cellular damage caused by reactive oxygen species that leads to cell death, ageing, or illness. Most physiological processes can result in OS, which in turn has been identified as a major cause of infertility. In promiscuous species, the fertilizing ability of the ejaculate partly determines the male reproductive success. When dominance determines access to fertile females, theory predicts that lower ranking males should increase resource investment into enhancing ejaculate quality. We hypothesized that subordinate males should thus prioritize antioxidant protection of their ejaculates to protect them from OS. We put this hypothesis to the test, by chronically dosing wild House Sparrows with diquat (∼1mg/kg), an herbicide that increases pro-oxidant generation. We found that, although they increased their antioxidant levels in the ejaculate, diquat-treated males produced sperm with reduced velocity. Importantly, and contrary to our hypothesis, males at the bottom of the hierarchy suffered the largest reduction in sperm velocity. We suggest that resource access hinders individuals' ability to cope with environmental hazards. Our results point at OS as a likely physiological mechanism mediating ejaculate quality, while individual ability to access resources may play a role in constraining the extent to which such resources can be allocated into the ejaculate.
   
Mots-clés oxidative stress, Social dominance, soma/germline allocation trade-off, sperm competition, sperm velocity, sperm motility, SOD, superoxide dismutase, Glutathione, pollutants, reproductive strategy, reproductive physiology
   
Citation Luis Rojas Mora, A., Firth, A., Blareau, S., Vallat, A., & Helfenstein, F. (2017). Oxidative stress affects sperm performance and ejaculate redox status in subordinate house sparrows. Journal of Experimental Biology, 220, 2577-2588.
   
Type Article de périodique (Anglais)
Date de publication 15-5-2017
Nom du périodique Journal of Experimental Biology
Volume 220
Pages 2577-2588
Liée au projet Oxidative stress in avian semen: causes and consequences ...