BELDEN, L.K.; Virginia Tech: Impact of euthrophication on wood frog tadpoles infected with trematode cercariae

Global environmental changes are likely to have profound impacts on disease dynamics in natural systems. To make predictions about what specific impacts are expected, one thing we need is a solid understanding of how the environmental context of host-parasite interactions can impact disease systems. I am examining the role of environmental context in a natural host-parasite system consisting of the parasitic trematode Echinostoma trivolvis, the first intermediate host snail, Helisoma trivolvis, and a second intermediate host, larval wood frogs, Rana sylvatica. In spring 2005, I examined the potential effect of eutrophication on larval wood frogs infected with E. trivolvis trematode cercariae collected from naturally infected H. trivolvis snails. Individual tadpoles were batch color marked with visible implant elastomer by treatment (no infection, 20 cercariae, 80 cercariae) and reared in mixed infection groups, 45 tadpoles/tank in outdoor 1000 L mesocosms that were either pre-treated with 20-25-5 fertilizer to create a eutrophic environment or were untreated controls. Survival to metamorphosis of the individuals in the highest infection treatment was reduced regardless of eutrophication treatment. For the surviving infected individuals, no impact on mass at metamorphosis was documented, although individuals were larger in the eutrophic tanks. These data demonstrate that infection with E. trivolvis can impact R. sylvatica survivorship and that eutrophication may have minimal impacts on hosts once infection has occurred.