Corticosterone selectively decreases humoral immunity in female eiders during incubation

Immunity is hypothesized to share limited resources with other physiological functions and this may partly account for the fitness costs of reproduction. Previous studies have shown that the acquired immunity of female common eider ducks (Somateria mollissima) is suppressed during their incubation, during which they entirely fast. Corticosterone was proposed to be an underlying physiological mechanism for such immunosuppression. Therefore, the current study aimed to assess the effects of exogenous corticosterone on acquired immunity in captive eiders. To this end, females were implanted with corticosterone pellets at different stages of their incubation fast. We measured total immunoglobulin levels, T-cell-mediated immune response, body mass and corticosterone levels in these females and compared them with those of control females prior to and after manipulation (i.e. corticosterone pellet implantation). To mimic corticosterone effects on body mass, we experimentally extended fasting duration in a group of females termed ;late fasters'..

Detailed foraging behavior of Adelie penguins from Adelie Land, East Antarctica, revealed by video and accelerometry loggers

第6回極域科学シンポジウム[OB] 極域生物圏11月16日（月）　国立極地研究所１階交流アトリウ

Triiodothyronine suppresses humoral immunity but not T-cell-mediated immune response in incubating female eiders (Somateria mollissima)

Immunity is believed to share limited resources with other physiological functions and this may partly account for the fitness costs of reproduction. Previous studies have shown that the acquired immunity of female common eiders (Somateria mollissima) is suppressed during the incubation fast. To save energy, triiodothyronine (T3) is adaptively decreased during fasting in most bird species, despite T3 levels are maintained throughout incubation in female eiders. However, the relationship between thyroid hormones and the immune system is not fully understood. The current study aimed to determine the endocrine mechanisms that underlie immunosuppression in incubating female eiders. ..

Innate immunity, assessed by plasma NO measurements, is not suppressed during the incubation fast in eiders

Immunity is hypothesized to share limited resources with other physiological functions and may mediate life history trade-offs, for example between reproduction and survival. However, vertebrate immune defense is a complex system that consists of three components. To date, no study has assessed all of these components for the same animal model and within a given situation. Previous studies have determined that the acquired immunity of common eiders (Somateria mollissima) is suppressed during incubation. The present paper aims to assess the innate immune response in fasting eiders in relation to their initial body condition. Innate immunity was assessed by measuring plasma nitric oxide (NO) levels, prior to and after injection of lipopolysaccharides (LPS), a method which is easily applicable to many wild animals. Body condition index and corticosterone levels were subsequently determined as indicators of body condition and stress level prior to LPS injection. The innate immune response in eiders did not vary significantly throughout the incubation period. The innate immune response of eiders did not vary significantly in relation to their initial body condition but decreased significantly when corticosterone levels increased. However, NO levels after LPS injection were significantly and positively related to initial body condition, while there was a significant negative relationship with plasma corticosterone levels. Our study suggests that female eiders preserve an effective innate immune response during incubation and this response might be partially determined by the initial body condition

Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins (Pygoscelis adeliae)

This study was financially supported by the following institutions: the WWF-UK through R. Downie, the Japanese Mombukagakusho and the Japanese Society for the Promotion of Science, the Zone Atelier Antarctique et Subantarctique –LTER France of the CNRS.The Southern Ocean is currently experiencing major environmental changes, including in sea‐ice cover. Such changes strongly influence ecosystem structure and functioning and affect the survival and reproduction of predators such as seabirds. These effects are likely mediated by reduced availability of food resources. As such, seabirds are reliable eco‐indicators of environmental conditions in the Antarctic region. Here, based on 9 years of sea‐ice data, we found that the breeding success of Adélie penguins (Pygoscelis adeliae) reaches a peak at intermediate sea‐ice cover (ca. 20%). We further examined the effects of sea‐ice conditions on the foraging activity of penguins, measured at multiple scales from individual dives to foraging trips. Analysis of temporal organisation of dives, including fractal and bout analyses, revealed an increasingly consistent behaviour during years with extensive sea‐ice cover. The relationship between several dive parameters and sea‐ice cover in the foraging area appears to be quadratic. In years of low and high sea‐ice cover, individuals adjusted their diving effort by generally diving deeper, more frequently and by resting at the surface between dives for shorter periods of time than in years with intermediate sea‐ice cover. Our study therefore suggests that sea‐ice cover is likely to affect the reproductive performance of Adélie penguins through its effects on foraging behaviour, as breeding success and most diving parameters share a common optimum. Some years, however, deviated from this general trend, suggesting that other factors (e.g. precipitation during the breeding season) might sometimes become preponderant over the sea‐ice effects on breeding and foraging performance. Our study highlights the value of monitoring fitness parameters and individual behaviour concomitantly over the long‐term to better characterize optimal environmental conditions and potential resilience of wildlife. Such an approach is crucial if we want to anticipate the effects of environmental change on Antarctic penguin populations.PostprintPeer reviewe

CORPS GRAS ET OBESITE Acides gras alimentaires et obésité : aspects qualitatifs et quantitatifs

Les triacylglycérols (TAG) adipocytaires représentent la principale forme de stockage des acides gras. Les TAG contiennent un mélange complexe d’acides gras qui diffèrent très nettement par leur structure moléculaire. En effet, les TAG adipocytaires contiennent un vaste spectre d’acides gras, allant en longueur de chaîne de 12 à 24 atomes de carbone et en insaturation de 0 à 6 doubles liaisons [1]. La nature des acides gras stockés dans le tissu adipeux dépend principalement de la composition en acides gras de l’alimentation [2, 3]. Le contrôle des acides gras et notamment des acides gras polyinsaturés (AGPI) stockés dans le tissu adipeux est encore assez peu compris. Si la composition en acides gras des TAG adipocytaires reflète largement celle de l’alimentation, elle ne la suit pas précisément [3]. Ainsi, la proportion en AGPI dans le tissu adipeux est systématiquement plus faible que celle du régime [2]. Une incorporation et une mobilisation sélectives de certains acides gras pourraient en partie expliquer ces observations. En effet, les AGPI sont globalement faiblement incorporés et assez facilement mobilisés. Nous n’aborderons pas ici la sélectivité du métabolisme adipocytaire des acides gras que nous avons précédemment rapportée à nos lecteurs (ocl, 5 : 199-205). Dans le cadre de cette revue, nous centrerons notre propos sur les relations entres acides gras alimentaires, développement du tissu adipeux et régulation de l’expression de gènes hépatiques et adipocytaires

CORPS GRAS ET OBESITE Acides gras alimentaires et obésité : aspects qualitatifs et quantitatifs

Les triacylglycérols (TAG) adipocytaires représentent la principale forme de stockage des acides gras. Les TAG contiennent un mélange complexe d’acides gras qui diffèrent très nettement par leur structure moléculaire. En effet, les TAG adipocytaires contiennent un vaste spectre d’acides gras, allant en longueur de chaîne de 12 à 24 atomes de carbone et en insaturation de 0 à 6 doubles liaisons [1]. La nature des acides gras stockés dans le tissu adipeux dépend principalement de la composition en acides gras de l’alimentation [2, 3]. Le contrôle des acides gras et notamment des acides gras polyinsaturés (AGPI) stockés dans le tissu adipeux est encore assez peu compris. Si la composition en acides gras des TAG adipocytaires reflète largement celle de l’alimentation, elle ne la suit pas précisément [3]. Ainsi, la proportion en AGPI dans le tissu adipeux est systématiquement plus faible que celle du régime [2]. Une incorporation et une mobilisation sélectives de certains acides gras pourraient en partie expliquer ces observations. En effet, les AGPI sont globalement faiblement incorporés et assez facilement mobilisés. Nous n’aborderons pas ici la sélectivité du métabolisme adipocytaire des acides gras que nous avons précédemment rapportée à nos lecteurs (ocl, 5 : 199-205). Dans le cadre de cette revue, nous centrerons notre propos sur les relations entres acides gras alimentaires, développement du tissu adipeux et régulation de l’expression de gènes hépatiques et adipocytaires