The combined influence of trematode parasites and predatory salamanders on wood frog (<Emphasis Type="Italic">Rana sylvatica</Emphasis>) tadpoles |
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Authors: | Lisa K Belden Jeremy M Wojdak |
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Institution: | (1) Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA;(2) Department of Biology, Radford University, Radford, VA 24142, USA |
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Abstract: | Predators can have important impacts on host–parasite dynamics. For many directly transmitted parasites, predators can reduce
transmission by removing the most heavily infected individuals from the population. Less is known about how predators might
influence parasite dynamics in systems where the parasite relies on vectors or multiple host species to complete their life
cycles. Digenetic trematodes are parasitic flatworms with complex life cycles typically involving three host species. They
are common parasites in freshwater systems containing aquatic snails, which serve as obligate first intermediate hosts, and
multiple trematode species use amphibians as second intermediate hosts. We experimentally examined the impact of predatory
salamanders (Ambystoma jeffersonianum) and trematode parasites (Echinostoma trivolvis and Ribeiroia ondatrae) on short-term survival of wood frog tadpoles (Rana sylvatica) in 150-L outdoor pools. Two trematode species were used in experiments because field surveys indicated the presence of both
species at our primary study site. Parasites and predators both significantly reduced tadpole survival in outdoor pools; after
6 days, tadpole survival was reduced from 100% in control pools to a mean of 46% in pools containing just parasites and a
mean of 49% in pools containing just predators. In pools containing both infected snails and predators, tadpole survival was
further reduced to a mean of 5%, a clear risk-enhancement or synergism. These dramatic results suggest that predators may
alter transmission dynamics of trematodes in natural systems, and that a complete understanding of host–parasite interactions
requires studying these interactions within the ecological framework of community interactions. |
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