Host sex and age influence endoparasite burdens in the gray XXXX lemur.

@entity1 @entity410 @entity19 @entity3794 @entity281
INTRODUCTION: Immunosenescence (deteriorating immune function at old age) affects @entity1 and laboratory animals, but little is known about immunosenescence in natural populations despite its potential importance for population and disease dynamics and individual @entity410 . Although life histories and immune system profiles often differ between the sexes, sex-specific effects of aging on health are rarely studied in the wild. Life history theory predicts that due to their shorter lifespan and higher investment into reproduction at the expense of immune defences, males might experience accelerated immunosenescence. We tested this hypothesis by examining sex-specific age trajectories of endoparasite burden (helminth prevalence and morphotype @entity3794 measured via fecal egg counts), an indicator of overall health, in wild gray @entity19 lemurs (Microcebus murinus). To account for potential interactions between seasonality and host sex or age we examined the predictors of parasite burdens separately for the dry and rainy season. RESULTS: Contrary to the prediction of immunosenescence, parasite prevalence and morphotype @entity3794 decreased at old age in the dry season, indicating acquired immunity by older animals. This pattern was primarily caused by within-individual decline in parasite loads rather than the earlier mortality of highly parasitized individuals. With the exception of an increasing cestode prevalence in males from yearlings to prime age in the rainy season, no evidence was found of male-biased ageing in parasite resistance. Besides this sex*age interaction, host age was uncorrelated with rainy season parasite loads. Seasonality did not affect the overall parasite loads but seasonal patterns were found in the predictors of parasite prevalence and morphotype @entity3794 . CONCLUSIONS: These results provide rare information about the age-related patterns of health in a wild vertebrate population and suggest improvement rather than senescence in the @entity281 at old age. Overall, males appear not to suffer from earlier immunosenescence relative to females. This may partially reflect the earlier mortality of males, which can render senescence difficult to detect. @entity281 are not strongly associated with survival in wild gray @entity19 lemurs, parasite load may, however, reflect overall good phenotypic quality of long-lived individuals, and is a potential correlate of @entity410 .
