Effects of juvenile infection on adult immunity and secondary sexual characters in a wolf spider

Abstract

The immunocompetence handicap hypothesis postulates that higher-quality males may be able to balance potential conflicts between resource-demanding activities, such as courtship behavior and immune responses, whereas lower-quality males suffer from immunosuppression or lower reproductive output. In this study, we examined the immune response of the brush-legged wolf spider Schizocosa ocreata to infection with pathogenic bacteria as juveniles (penultimate), and its impact on development of adult male secondary sexual signaling traits. After oral ingestion of a bacterial pathogen, active bacteria were found in the hemolymph for up to 5h. We found that immune activation (ingestion of bacteria) at the juvenile stage resulted in higher immune response as an adult than control individuals, but also led to lower body condition index values and a higher degree of asymmetry in secondary sexual signaling traits (foreleg tufts). Infected males also had relatively smaller tufts than control males when penultimate body condition was added as a covariate and tuft size was appropriately scaled. Additionally, males infected as juveniles had significantly lower mating success than control males, although this difference was not due to courtship vigor. These results suggest that during development, juvenile males may be allocating more resources into immune function during infection, potentially at the cost of reduced sexual signaling and mating success as adults, and that there is the potential for complex trade-offs between immunity and sexual signaling in this species.