Meeting Abstract
Responding to an immune challenge is costly, and animals vary in how they deal with these costs. In some cases, individuals responding to an immune challenge appear to prioritize survival at the cost of reduced future reproduction. In other cases, individuals appear to interpret an immune challenge as a threat of death, leading to terminal (i.e., increased) investment in reproduction and decreased investment in immunity. Life history stage may influence which outcome occurs. We predicted that individuals who were juveniles when challenged should prioritize survival in order to reach reproductive age, even at the cost of reduced future reproduction. In contrast, individuals of reproductive age should be more likely to exhibit terminal investment. We challenged the immune systems of both male and female Pacific field crickets, Teleogryllus oceanicus, at four life history stages: last juvenile instar, immediately after adult molt, after reproductive maturity but pre-mating, and post-mating. We measured immune response with biochemical assays of two key immune system components. We measured reproductive effort by assessing time to reproductive maturity in individuals challenged as juveniles, responsiveness to mating opportunities in all individuals, and song characteristics in males. We found that an individual’s age at immune challenge did affect both its immune response and behavioral responses to immune challenge, but not always in the predicted direction.
