Female Salamanders Experience Higher Parasitism Compared to Males: A Cost of Female Reproduction?

Abstract

Males tend to experience higher rates of parasitism compared to females, a phenomenon associated with ecological factors, the fact that males engage in risky behaviors, and because testosterone is known to be immunosuppressive. However, females could experience higher rates of parasitism if energy is allocated from costly immune responses towards producing eggs. We used pooled data sets from laboratory experiments to investigate sex-specific differences in salamander (Plethodon cinereus) resistance to the emerging fungal pathogen Batrachochytrium dendrobatidis (“Bd”). Contrary to our predictions, we found that female salamanders had a higher prevalence of infection (∼56%) and carried a higher Bd infection burden (455 zoospores equivalents per sample) compared to male salamanders (which had a Bd infection prevalence of ∼24% and an average infection burden of 58 zoospore equivalents per sample). We also found that female reproductive investment (i.e., mass of eggs) positively correlated with Bd infection burden, suggesting that females who previously invested more into reproduction carried a higher Bd infection burden. Collectively, our findings might indicate that female salamanders experience a cost of reproduction in the form of decreased disease resistance.