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Helfenstein, Fabrice

Nom
Helfenstein, Fabrice
Affiliation principale
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/762

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  • Publication
    Métadonnées seulement
    Modification of sperm quality after sexual abstinence in the Seba's short tailed bat (Carollia perspicillata)
    (2016-5-4)
    Wesseling, Charlotte
    ;
    Fasel, Nicolas Jean
    ;
    Richner, Heinz
    ;
    Helfenstein, Fabrice 
    In polygynous mating systems, few males have stable access to sexual mates. With an expected higher copulation rate, harem males may deplete seminal fluids or increase epididymal sperm maturation, generating poor sperm quality. In a first study, we reported a higher sperm quality in sneaker males of Carollia perspicillata. To test whether the lower sperm quality observed in harem males was generated by an elevated copulation rate, we temporarily removed males of both social statuses from the colony. We thus assessed status-related changes of sperm quality resulting from sexual abstinence. Moreover, released from territory and female guarding, harem males were expected to show a reduction in somatic costs. On the basis of sperm competition models, we predicted a higher resource investment in the ejaculate with the reduction of pre-copulatory efforts. In line with our predictions, sperm quality of harem males improved significantly in contrast to sneaker males, whose sperm quality did not change. Without an increase in ejaculate lipid peroxidation, our results also provide evidence that the duration of sexual abstinence was not sufficient to generate sperm oxidative damage through senescence. Harem males did not show a reduction in blood lipid peroxidation or in the ratio of oxidized to reduced glutathione. In line with the maintenance of these somatic costs, harem males did not invest more superoxide dismutase to the ejaculate to maintain sperm quality. Our results suggest that a difference in copulation rate rather than an adaptation to sperm competition provides sneaker males with higher sperm quality in C. perspicillata.
  • Publication
    Métadonnées seulement
    Nestling erythrocyte resistance to oxidative stress predicts fledging success but not local recruitment in a wild bird
    (2013)
    Losdat, Sylvain
    ;
    Helfenstein, Fabrice 
    ;
    Blount, Jonathan D.
    ;
    Marri, V.
    ;
    Maronde, L.
    ;
    Richner, Heinz
    Stressful conditions experienced by individuals during their early development have long-term consequences on various life-history traits such as survival until first reproduction. Oxidative stress has been shown to affect various fitness-related traits and to influence key evolutionary trade-offs but whether an individual's ability to resist oxidative stress in early life affects its survival has rarely been tested. In the present study, we used four years of data obtained from a free-living great tit population (Parus major; n = 1658 offspring) to test whether pre-fledging resistance to oxidative stress, measured as erythrocyte resistance to oxidative stress and oxidative damage to lipids, predicted fledging success and local recruitment. Fledging success and local recruitment, both major correlates of survival, were primarily influenced by offspring body mass prior to fledging. We found that pre-fledging erythrocyte resistance to oxidative stress predicted fledging success, suggesting that individual resistance to oxidative stress is related to short-term survival. However, local recruitment was not influenced by pre-fledging erythrocyte resistance to oxidative stress or oxidative damage. Our results suggest that an individual ability to resist oxidative stress at the offspring stage predicts short-term survival but does not influence survival later in life.