Distribution of Lymnaeid Snail Hosts of the Giant Liver Fluke in Northeastern Minnesota

Abstract

Lymnaeid snails are important intermediate hosts for many trematode parasites, such as the giant liver fluke, but little is known about their habitat associations. Lymnaied snail surveys were conducted across St. Louis County and Lake County in 2015. 84 locations were sampled for snails and several habitat variables were measured (calcium carbonate, substrate type, lake area, pH, etc.). ArcGIS data was queried to obtain landscape variables such as cover type near sampling locations. Lymnaea megasoma, L. stagnalis, L. elodes, L. catascopium, and Fossaria spp. were found in the study area. Lymnaea megasoma L. elodes, and Fossaria spp species were associated with higher CaCO3 concentrations compared to locations without these species. L. megasoma was associated with smaller proportions of open water on the landscape scale, suggesting this species favors quiet bays and stagnant channels. Fossaria spp. were not found in close association with open water suggesting this species inhabits small woodland ponds and vernal pools. No giant liver fluke cercariae were found during this survey. However, xiphidiocercariae and strigea cercariae were found in the study area. Xiphidiocercariae cercariae were not associated with higher CaCO3 concentrations (mean with cercariae = 59 ppm; without cercariae = 58 ppm). Strigea cercariae were associated with higher CaCO3 concentrations (mean with cercariae = 91 ppm; without cercariae = 58 ppm). Infection with either one of these cercariae decreased survival time in L. megasoma. L. megasoma warrants futher study as this species is restricted to the Great Lakes basin and may be an important wildlife parasite intermediate host in this area.