Host and parasite counteradaptations: an example from a freshwater snail.
Trematode infection of pulmonate snails is often associated with increased growth and/or survivorship of snail hosts. The freshwater pulmonate Lymnaea elodes and its trematode parasites are used to test whether this increase is a parasite adaptation, a host adaptation, or a side effect that serves no adaptive function for either participant. Field experiments indicate that trematode parasitism significantly reduces host fecundity and causes a temporary elevation and subsequent reduction in host growth. A 2- yr field survey of the prevalence of trematode infection in 3 snail populations revealed a significant positive relationship between shell size and prevalence. L. elodes does not outlive its trematode infections. Overall, results suggest that increased survivorship in trematode-infected L. elodes is a parasite strategy for providing a stable, long-term resource for the parasite. -from Authors
Minchella, D., Leathers, B., Brown, K., & McNair, J. (1985). Host and parasite counteradaptations: an example from a freshwater snail.. American Naturalist. Retrieved from https://ir.una.edu/eng_facpub/63