Impact of eutrophication on wood frog, Rana sylvatica, tadpoles infected with Echinostoma trivolvis cercariae

In freshwater systems, environmental changes, such as eutrophication, are occurring that could impact the outcome of host-parasite interactions. Using tadpole infection with trematode cercariae as a host-parasite system, this study examined (i) growth, development, and maintenance of trematode (Echinostoma trivolvis (Cort, 1914)) infection levels in second intermediate host larval wood frogs (Rana sylvatica LeConte, 1825) and (ii) post-infection impacts of eutrophication on R. sylvatica tadpoles infected to varying degrees with E. trivolvis cercariae. Results from the first experiment suggest no impact of infection with 50 cercariae on R. sylvatica growth and development compared with uninfected controls. Results from the second experiment, investigating the impact of eutrophication on infected tadpoles, showed that survival to metamorphosis of the individuals in the highest infection treatment (80 cercariae) was reduced regardless of eutrophication treatment. However, for individuals surviving infection with 80 cercariae and for individuals infected with only 20 cercariae, no impact of infection on mass at metamorphosis was documented, although individuals were larger at metamorphosis in the eutrophic tanks. These data demonstrate that infection with E. trivolvis can impact R. sylvatica survivorship, at least above some threshold infection level, and that eutrophication may have minimal impacts on tadpole hosts once infection has occurred.