Date of Award

Summer 4-29-2025

Document Type

Honors Project

Degree Name

Bachelor of Science

Department

Biological Sciences

Department Chair or Program Director

Dianne Baker

First Advisor

Abbie Tomba

Major or Concentration

Biology

Abstract

Snails are important in freshwater ecosystems as primary consumers and are good indicators of the stability of a habitat. Trematodes are parasitic flatworms that infect freshwater snails and can cause changes in metabolic function and growth. Flow rates and water levels are now more variable due to climate change, increasing stress and dislodgment in the snail population. This study investigates how parasites, shell morphology, and native flow environment influence resistance to disturbance. Elimia populations were sampled for differences in parasitism, shell morphology, and ability to withstand high flow environments in two different rivers. Sample sites at the Potomac River were tidal with low flow, while sites at the Rappahannock River were higher flow with pools and riffles. Approximately 10 quadrats (0.09 m2) were randomly selected for sampling per sample site. The Rappahannock was sampled four times at three sites, while the Potomac was sampled four times at two sites. Snails were dissected and measured for shell morphological features, looking specifically at width and aperture. Shell width, shell aperture, and shell thickness in the Potomac was significantly larger than in the Rappahannock (Wilcoxon p< 0.0001). In both rivers, shell widths and apertures were both significantly larger in infected snails than non-infected snails (Wilcoxon p< 0.001). Prevalence of parasitism did not differ between rivers (Χ2 p=0.51). To measure snails' response to high flow, approximately 300 live snails were collected per sample location and were subjected to a high flow environment (0.75 m/s) for 10 minutes to determine time of dislodgment. In a population of all snails, sex was the only determinant of time of dislodgment (multiple regression p=0.032). Longer, skinnier apertures lead to increased time of dislodgment in males; wider and longer apertures lead to increased time of dislodgment in females.

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