Abstracts (first author)
The role of maternal effects on the ontogeny of constitutive immunity in wild birds
The ability to resist infections early in life is expected to be under intense selection pressure because infection may have severe impact on fitness. Maternally transmitted immune components provide some protection during early stages and may have long-lasting effects on the development of the humoral immune system. Extrinsic influences on mothers (i.e. exposure to pathogens) may also influence vertical transmission of immune components to offspring. However, maternal effects on the ontogeny of offspring immune function may not be restricted to vertically transmitted components. Mothers may influence the development of offspring immune function by providing a suitable environment for embryo development through parental care. Indeed, parental behaviour in birds plays an important role in keeping embryo thermal conditions within the optimal range for development. This parentally induced variation in embryo temperatures can thereby influence development and performance of the immune system. Yet, whether these maternal effects mediated by egg constituents or thermal environment interact with endogenous development of immune function differently among species remains unstudied. In this study, we examined the ontogeny of constitutive immunity in relation to developmental stage in a group of 22 Passerine bird species. Our results show that inter-specific variation in immune activity at hatching was mainly explained by extrinsic factors mediated by the mother, suggesting an important role of maternal effects on offspring immunity at hatching. Activity of constitutive components of the immune defense was detected as early as 1-3 days post-hatching, and increasing with age, indicating that immune function in older nestlings reflects intrinsic development. Our results highlight both endogenous immune activity of altricial nestlings at an early developmental stage, and maternal effects on the ontogeny of immune function of young birds.