FESTERING FOOD: CHYTRIDIOMYCETE PATHOGEN REDUCES QUALITY OF DAPHNIA HOST AS A FOOD RESOURCE

When parasitic infections are severe or highly prevalent among prey, a significant component of the predator's diet may consist of parasitized hosts. However, despite the ubiquity of parasites in most food webs, comparisons of the nutritional quality of prey as a function of infection status are largely absent. We measured the nutritional consequences of chytridiomycete infections in Daphnia, which achieve high prevalence in lake ecosystems (>80%), and tested the hypothesis that Daphnia pulicaria infected with Polycaryum laeve are diminished in food quality relative to uninfected hosts. Compared with uninfected adults, infected individuals were smaller, contained less nitrogen and phosphorus, and were lower in several important fatty acids. Infected zooplankton had significantly shorter carapace lengths (8%) and lower mass (8–20%) than uninfected individuals. Parasitized animals contained significantly less phosphorus (16–18% less by dry mass) and nitrogen (4–6% less) than did healthy individuals. Infecte...