LOVE, OP*; SALVANTE, KG*; DALE, J; WILLIAMS, TD; Simon Fraser University; Simon Fraser University; Simon Fraser University; Simon Fraser University: Intersexual differences in immunity through different life-history stages

The study of immunity has become an important focus of numerous studies on fitness-related trade-offs. In particular, researchers have examined potential trade-offs between immune function and such traits as survival, breeding performance, fecundity and growth. However, the majority of studies typically measure immunocompetance in individuals at a single point in time. It is currently not well understood how immunity changes across different life-history stages and whether these changes differ for males and females. Here we examine inter-sexual differences in immune function through all major life-history stages in a captive colony of zebra finches (Taeniopygia guttata) using a measure of both cell-mediated (PHA) and humoral (SRBC) immunity. We measured immunocompetance in juveniles from fledging to first molt to adult-non-breeding stages. In breeding birds, we measured immunocompetance during egg-laying and at the end of parental care. Differences between the sexes were weak in juveniles suggesting each sex is under similar physiological demands at this point. During breeding, differences between the sexes were more pronounced, with females exhibiting the lowest responses during egg-laying. Our results provide an examination of immunity during key points in an animal�s life, and suggest that immunocompetance varies significantly between the sexes across different life-history stages. This intersexual ontogenetic variation in immunocompetance should be carefully considered in future studies of immunity.