Sex differences in parasitic infections among arthropod hosts: is there a male bias?

A higher susceptibility to diseases or parasites in males than females may be an ultimate consequence of the different reproductive strategies Favored by selection in the two sexes. At the proximate level, the immunosuppressa nt effects of testosterone in vertebrates provide a mechanism that can caus e male biases in parasite infections. Invertebrates, however, lack testoste rone and other steroid hormones. We used a meta-analysis of published resul ts to investigate whether sex biases in parasite infections were generally observed among arthropod hosts despite the absence of the immune-endocrine coupling provided by testosterone. Overall, male and female arthropods did not differ in prevalence or intensity of parasite infections. This is based on an analysis of sex differences corrected for sample size and, when poss ible, variability in the original data. Sex biases in parasite infection we re not more likely to be observed in certain host or parasite taxa, and wer e not more pronounced in experimental studies than in surveys of naturally infected hosts. Our results suggest that because of the absence of endocrin e-immune interactions in arthropods. males are not generally more prone to parasite infections than females despite the greater intensity of sexual se lection acting on males.