FEDORKA, KM*; ZUK, M; University of California, Riverside; University of California, Riverside: Reproductive behavior and immune defense in the striped ground cricket

Biologists have recently become interested in how variance in immune effector systems may translate into variance in fitness. To this end, the rapidly developing field of ecological immunity has begun to focus on how individual immunocompetence relates to both expensive life history trade-offs and to sexual selection. Although theoretical and empirical works have investigated the immuno-suppressive costs of reproduction and the evolution of honest signals of parasitic resistance, these concepts remain controversial. Here, we address these concepts in the striped ground cricket, Allonemobius socius; a system where males provide a hemolymph nuptial gift to females during copulation. Considering the central role hemolymph plays in invertebrate immunity, we hypothesized that a male�s ability to rebut future parasitic challenges would be reduced as a consequence of mating; furthermore, that the hemolymph gift provides females with information regarding a male�s immunocompetence. To test these ideas, we examined the hemolymph immune properties (e.g. hemocyte load, encapsulation ability, phenoloxidase and lytic activity) of both sexes as it related to mating history and behavior. Our data suggest that reproduction exerts a strong immuno-suppressive cost on both sexes; however, multiply mated males exhibited a greater reduction in hemolymph immune properties than females. In addition, females modified their mating behavior (e.g. time spent in copula) in accordance with male hemolymph quality, suggesting that the nuptial gift may act as an honest indicator of the male�s ability to mount a successful immune defense.