Citation:

FORSHAY, K. J., P. T. Johnson, M. Stock, C. Penalva, AND S. I. Dodson. FESTERING FOOD: CHYTRIDIOMYCETE PATHOGEN REDUCES QUALITY OF DAPHNIA HOST AS A FOOD RESOURCE. ECOLOGY. Ecological Society of America, Ithaca, NY, 89(10):2692-2699, (2008).

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Journal Article

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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, that 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 lacked essential fatty acids. Infected zooplankton had significantly shorter carapace lengths (8%) than gravid females and lower in mass (8 to 20%) than both non-gravid and gravid uninfected individuals. Per gram dry weight parasitized animals contained significantly less phosphorus (16 to 18%) and nitrogen (4 to 6%) than did healthy individuals. Infected individuals also contained 26 to 34% less saturated fatty acid and 31 to 42% less docosahexaenoic acid, an essential fatty acid critical to fish growth. Our results suggest that naturally-occurring levels of chytrid infections in D. pulicaria populations reduce the quality of food available to secondary consumers, including planktivorous fishes, with potentially important effects for lake food webs.

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