Parasites can strongly affect host populations, but these effects may depend on community context. In addition to directly affecting host mortality and fecundity, parasites may also affect traits that alter the susceptibility of their hosts to predators. Echinostomes are an emerging parasite of amphibians whose effects on hosts are not well understood. In collaboration with Dr. Manja Holland, I performed a field survey to determine the distribution of echinostomes among a series of ponds in southeastern Michigan. I then performed two experiments in order to 1) measure the effects of infection on larval green frog (Rana clamitans) hosts, including mortality and also behavior, which may affect interactions with other species, and 2) determine the extent to which infection affects dragonfly (Anax junius) predation rate on green frog hosts.
Results/Conclusions
In the survey, we observed that one species of echinostome, Echinoparyphium cinctum, was present in several ponds known to contain larval green frog populations. In my first experiment, echinostome infection had a strong effect on green frog mortality (ANOVA, p<0.05), but behavior (activity level and vertical distribution) was not significantly affected by infection. In my second experiment, echinostome infection did not have a significant effect on predation susceptibility, although infected individuals tended to avoid predation longer. The results offer new insight into the range of effects of echinostomes on their amphibian hosts, and may have implications for host population dynamics.
