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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
    Reproductive effort and oxidative stress: effects of offspring sex and number on the physiological state of a long-lived bird
    (2017-2-13)
    Merkling, Thomas
    ;
    Blanchard, Pierrick
    ;
    Chastel, Olivier
    ;
    Glauser, Gaëtan 
    ;
    Vallat, Armelle
    ;
    Hatch, Scott A.
    ;
    Danchin, Etienne
    ;
    Helfenstein, Fabrice 
    1. Individuals must trade-off between energetically costly activities to maximize their fitness. However, the underlying physiological mechanism remains elusive. Oxidative stress, the imbalance between reactive oxygen species production and antioxidant and/or repair activities, has been suggested to underlie life-history trade-offs: greater investment in reproduction supposedly generating higher oxidative damage, thus reducing life span. 2. While most studies used natural or experimental variation in offspring number to examine how reproduction affects oxidative stress, none studied the impact of offspring sex, although it could influence physiological costs and fitness, if the sexes differ in terms of energetic cost. 3. Here, we aim at further understanding how reproduction (in terms of offspring sex, experimentally manipulated and number, not manipulated) influences oxidative stress in a wild seabird, where sons are energetically costlier than daughters. We did so by conducting a chick fostering experiment (to disentangle foster and produced sex ratio) and using four oxidative stress markers plus baseline corticosterone. 4. First, the results suggest that individual physiological state before laying modulates upcoming reproductive effort. Individuals with higher pre-laying baseline corticosterone and lower antioxidant activity, estimated by their superoxide dismutase activity, subsequently invested more in reproduction, estimated by the cumulative number of days spent rearing chicks. Hence, it seems that only individuals that could afford to invest heavily in reproduction did so. 5. Then, we examined the effects of reproductive effort on individual physiological state at the end of the breeding season. Higher reproductive effort seemed to imply higher physiological costs. Oxidative stress, estimated by the ratio of oxidized over reduced glutathione, increased with more male-biased foster sex ratio among mothers but not among fathers, whereas baseline corticosterone did so in both sexes. Similarly, lipid oxidative damage to red blood cells increased with increasing cumulative number of days spent rearing chicks. 6. Our study provides the first evidence that brood sex ratio variation can affect oxidative balance, potentially in a sex-specific way, although more studies are needed to understand whether the observed physiological costs could lead to fitness costs. It also highlights the need to consider sex ratio in future studies investigating the role of oxidative stress in life-history trade-offs.
  • Publication
    Métadonnées seulement
    Maternal effects as drivers of sibling competition in a parent–offspring conflict context? An experimental test
    (2016-5-3)
    Merkling, Thomas
    ;
    Perrot, Charlotte
    ;
    Helfenstein, Fabrice 
    ;
    Ferdy, Jean-Baptiste
    ;
    Gaillard, Laurent
    ;
    Lefol, Emilie
    ;
    Voisin, Emmanuelle
    ;
    Hatch, Scott A.
    ;
    Danchin, Etienne
    ;
    Blanchard, Pierrick
    Maternal effects occur when the mother's phenotype influences her offspring's phenotype. In birds, differential allocation in egg yolk components can allow mothers to compensate for the competitive disadvantage of junior chicks. We hypothesize that the parent–older chick conflict peaks at intermediate conditions: parents benefit from the younger chick(s) survival, but its death benefits the older chick in terms of growth and survival. We thus expect maternal compensation to follow a bell-shaped pattern in relation to environmental conditions. We studied a black-legged kittiwake (Rissa tridactyla) population where previous results revealed increased allocation of yolk testosterone in younger as compared to older chicks in intermediate conditions, in line with our theoretical framework. We therefore predicted a maternally induced increase in aggressiveness, growth, and survival for younger chicks born in intermediate environmental conditions. Controlling for parental effects and chick sex, we manipulated food availability before egg laying to create a situation with intermediate (Unfed group) and good (Fed group) environmental conditions. Within each feeding treatment, we further created experimental broods where the natural hatching order was reversed to maximize our chances to observe an effect of feeding treatment on the younger chicks' aggressiveness. As predicted, we found that chick aggressiveness was higher in younger chicks born from the Unfed group (i.e., in intermediate environmental conditions), but only when they were put in a senior position, in reversed broods. Predictions on growth and survival were not confirmed. Mothers thus seem to favor the competitiveness of their younger chick in intermediate conditions via egg yolk components, but our study also suggests that hatching asynchrony need to be small for maternal compensation to be efficient. We emphasize the need for further studies investigating other chick behaviors (e.g., begging) and focusing on the relative role of different yolk components in shaping parent–offspring conflict over sibling competition.
  • Publication
    Métadonnées seulement
    Behavioral and physiological responses to male handicap in chick-rearing black-legged kittiwakes
    (2011)
    Leclaire, Sarah
    ;
    Bourret, Vincent
    ;
    Wagner, Richard H.
    ;
    Hatch, Scott A.
    ;
    Helfenstein, Fabrice 
    ;
    Chastel, Olivier
    ;
    Danchin, Etienne
  • Publication
    Métadonnées seulement
    Family size and sex-specific parental effort in black-legged kittiwakes
    (2010)
    Leclaire, Sarah
    ;
    Helfenstein, Fabrice 
    ;
    Degeorges, Anne
    ;
    Wagner, Richard H.
    ;
    Danchin, Etienne
  • Publication
    Métadonnées seulement
    Evidence that pairing with genetically similar mates is maladaptive in a monogamous bird
    (2009)
    Mulard, Hervé
    ;
    Danchin, Etienne
    ;
    Talbot, Sandra L.
    ;
    Ramey, Andrew M.
    ;
    Hatch, Scott A.
    ;
    White, Joël F.
    ;
    Helfenstein, Fabrice 
    ;
    Wagner, Richard H.
  • Publication
    Métadonnées seulement
    Multiple deleterious effects of experimentally aged sperm in a monogamous bird
    (2008)
    White, Joël
    ;
    Wagner, Richard H.
    ;
    Helfenstein, Fabrice 
    ;
    Hatch, Scott A.
    ;
    Mulard, Hervé
    ;
    Naves, Liliana C.
    ;
    Danchin, Etienne
  • Publication
    Métadonnées seulement
  • Publication
    Métadonnées seulement
    Female choice of young sperm in a genetically monogamous bird
    (2004)
    Wagner, Richard H.
    ;
    Helfenstein, Fabrice 
    ;
    Danchin, Etienne
  • Publication
    Métadonnées seulement
  • Publication
    Métadonnées seulement
    Is male unpredictability a paternity assurance strategy?
    (2004)
    Helfenstein, Fabrice 
    ;
    Danchin, Etienne
    ;
    Wagner, Richard H.