Are immune responses gender-related in Carabus lefebvrei (Coleoptera: Carabidae)?

Abstract

The “live hard, die young” theory predicts the evolution of gender differences in immunocompetence, with males having a weaker immune system than females. To test this hypothesis in Carabus lefebvrei, total and basal phenoloxidase (PO) activities and lysozyme-like enzyme activity were compared among males and females of different reproductive status. The sexual dimorphism occurred only in reproductively active adults and for total and basal PO levels, while no significant differences were recorded between sexes in virgin adults. Differences were not recorded for lytic activity between sexes. Basal PO and lytic activities decreased in both males and females after mating, while the total PO value increased in males and decreased in females. Thus, resources seem to be invested to increase the humoral response in pre-reproductive phase forming a barrier against pathogens and preserving the fecundity and longevity of both sexes. Males preserve their survivorship in reproductive phase by increasing enzymatic levels in hemolymph to avoid fitness reduction due to the increased exposure to pathogen as result of mating. Females shift resources from PO and lytic activity to other physiological systems involved in reproduction in order to maximize their fitness.

Keywords

• ecological immunology; life history; lytic activity; phenoloxidase; sexual dimorphism