Parasite Communities and Reproductive Consequences of Infection in Native Elimia virginica and Invasive Margarya chinensis In Mid-Atlantic Water Systems

Abstract

Freshwater gastropods play many important ecological roles in aquatic ecosystems while serving as intermediate hosts for numerous parasite species, particularly trematodes. Non-native species have the potential to alter parasite transmission cycles and host-parasite interactions within local ecosystems. Alternatively, they can lack parasites entirely (enemy release hypothesis), providing a competitive advantage over native species. Parasite communities are often understudied, including gastropods in Virginia river systems where non-native Japanese mystery snails (Heterogen japonica) are present and have previously been found infected with Aspidogaster trematodes. To address this knowledge gap, native E. virginica and H. japonica were collected from the Rappahannock and Potomac river systems in Virginia from 2018-2026. For each snail, length, sex, and brood count data were collected, and snails were dissected to screen for parasites. For both sites and all years, E. virginica had higher parasite diversity than mystery snails. However, mystery snails had a high prevalence of the trematode Aspidogaster conchicola (average 37%) and unidentified digenean metacercaria. Native E. virginica were infected with A. conchicola (average 2.6%) and up to four morphotypes of digenean trematode cercaria. Aspidogaster infection was associated with a significant reduction in brood size in mystery snails, with infected individuals possessing fewer juveniles than uninfected snails. These findings suggest that parasite infection imposes measurable reproductive costs on mystery snails. This study demonstrates that parasites have the potential to impair reproductive ability, contributing to regulation of invasive snail populations and also improves our understanding of parasite ecology in Mid-Atlantic freshwater ecosystems.