Effects of Trematode Infection on Aspects of Performance in Freshwater Snails

Many snail species are commonly infected with trematode parasites. These parasites use snails as intermediate hosts in their typically complex life cycles. Trematodes can affect the behavior and phenotype of many different species of animals that they use as hosts, and this series of projects examines how trematodes might affect the performance of the feet of two different snail species: a pond-dwelling snail (Physa gyrina) and a stream-dwelling snail (Elimia potosiensis).

	Snails use their feet to hold themselves in position against changes in water velocity and to move from place to place. We are evaluating how snails hold their feet against the substrate by photographing snails from below clear acrylic plates, and measuring foot size and shape in defensive (left) and normal movement (middle) postures; all foot measurements are scaled against shell measurements (right) taken from the same position after making the snail retract its foot. (Physa above and Elimia below.)
	Snails are collected from field sites around the SIUE campus and in Missouri. Here, Chris and Rhys are measuring current velocities and collecting Elimia individuals from the Meramec River near Meramec Caverns.
	We are developing techniques to test the tenacity of snails as they try to resist being dislodged in flowing water; we also are examining the behavioral response of snails to current based on their infection status. Chris and John O'Flaherty are shown here using our laboratory flume to calibrate a thermistor-based flow meter to be used at field sites.

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