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Glauser, Gaëtan

Nom
Glauser, Gaëtan
Affiliation principale
Email
gaetan.glauser@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/369
_
0000-0002-0983-8614

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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
    Alternative reproductive tactics, sperm mobility, and oxidative stress in Carollia perspicillata (Seba's short-tailed bat)
    (2017-1-1)
    Fasel, Nicolas Jean
    ;
    Wesseling, Charlotte
    ;
    Fernandez, Ahana Aurora
    ;
    Vallat, Armelle
    ;
    Glauser, Gaëtan 
    ;
    Helfenstein, Fabrice 
    ;
    Richner, Heinz
    In social systems with alternative reproductive tactics, sneakers face a stronger sperm competition than harem males, and hence are predicted to allocate more resources to ejaculates. Antioxidants can protect sperm against oxidative stress, and thus their allocation to the ejaculate may depend on social status. In this study on the frugivorous bat Carollia perspicillata, we assessed for harem and sneaker males, four sperm mobility traits, blood and ejaculate markers of the redox balance, and the ejaculate to blood ratios of the redox markers. Under higher sperm competition, sneaker males should allocate proportionally more antioxidant resources to the protection of sperm than harem males. In contrast, harem males should favour pre-copulatory functions, which comprise the protection of blood. We found significantly higher sperm velocity and sperm survival in sneakers. There was no correlation between sperm mobility and sperm enzymatic antioxidant activity or ejaculate levels of lipid peroxidation (oxidative damage). Ejaculate levels of lipid peroxidation and sperm survival showed a significantly positive correlation, which could be attributed to the role of reactive oxygen species for sperm capacitation. Harem and sneaker males showed similar levels of redox balance markers in ejaculate and blood. However, harem males showed a higher ratio of oxidized over reduced glutathione in blood, which may indicate higher cellular stress due to higher metabolism. Overall, our findings suggest that sneakers of C. perspicillata compensate for a stronger sperm competition by higher sperm mobility.
  • Publication
    Métadonnées seulement
    Corticosterone: effects on feather quality and deposition into feathers
    (2015-2-1)
    Jenni-Eiermann, Susanne
    ;
    Helfenstein, Fabrice 
    ;
    Vallat, Armelle
    ;
    Glauser, Gaëtan 
    ;
    Jenni, Lukas
    The concentration of the glucocorticoid hormone corticosterone (CORT) is increasingly used in ecology and conservation biology as an integrated measure of the historical record of an individual's hypothalamo–pituitary–adrenal (HPA) activity during feather growth. However, where and how CORT is incorporated in feathers is incompletely known. * We therefore examined whether CORT is reliably measured with an enzyme immunoassay, where CORT is incorporated in the feather and where it affects feather quality, and whether CORT incorporation is related to plasma CORT levels, feather growth rate and melanin pigmentation. * During the regrowth of plucked tail feathers, we injected pigeons with tritium-labelled CORT, and implanted a CORT-releasing pellet to increase plasma CORT concentration for about 3 days. In feather segments, we measured labelled CORT (DPM3H) and we quantified CORT with an enzyme immunoassay EIA (CORTEIA) and double-checked the results with ultra-high performance liquid chromatography–tandem mass spectrometry (LCMS) (CORTMS). * Administered CORT affected feather structure and colour at the very base of the feather (epidermal collar, ramogenic zone) and reduced growth rate. In contrast, incorporation of CORT into the feather happened mainly in the blood quill, as shown with all three methods (DPM3H, CORTEIA and CORTMS). * Incorporation of CORT into feathers was only roughly proportional to plasma concentration, proportional to feather growth rate and increased with melanin pigmentation. * Measuring CORT in feather is a way to reveal past events of increased stress during feather growth in birds.