Sex matters: effects of sex and mating in the presence and absence of a protective microbe

Abstract

In most animals, female investment in offspring production is greater than for males. Lifetime reproductive success (LRS) is predicted to be optimised in females through extended lifespans to maximise reproductive events. Extended lifespan can be achieved through increased investment in immunity. Males, however, maximise lifetime reproductive success by obtaining as many matings as possible. Microbe-mediated protection (MMP) is known to affect both immunity and reproduction, but whether the two sexes respond differently to the provision of MMP remains to be explored. Here, we investigated the sex-specific differences in host life history traits between female and male Caenorhabditis elegans following pathogenic infection with Staphylococcus aureus with or without MMP by Enterococcus faecalis. Overall, female survival decreased with increased mating. With MMP, females increased investment into offspring production, while males displayed higher behavioural activity. These results highlight the different strategies employed by the two sexes under pathogen infection with and without MMP.