Movement alterations of Physa gyrina when parasitized.

Abstract

Physa gyrina are a common freshwater snail that serves as the intermediate host for many digenetic trematode parasites. For this study, Physa gyrina were collected from Alanson Ditch, Emmet County, Michigan, and put into a light box so that infected snails would shed their cercariae. The infected snails were then separated from the non-infected snails. A test of movement was carried out on the infected and non-infected snails by placing them in a 30-gallon aquarium and monitoring their movement. Infected snails were compared to non-infected snails. The hypotheses were that infected snails would be larger in size and move slower than non-infected snails. The data showed that non-infected Physa gyrina moved further laterally, than infected ones (T-test, p = 0.054) and that infected Physa gyrina moved faster overall than non-infected Physa gyrina (T-test, p = 0.066). There was no signficant variation of average overall shell volume (mm3) between infected and non-infected Physa gyrina (mean standard deviation = 29mm), (T-test, p = 0.354, n infected = 10, n uninfected = 14). There was also no significant variation of vertical distance traveled between infected and non-infected Physa gyrina (T-test, p x = 0.924, p y = 0.223). Futher studies should use a larger sample size, conduct research over a longer period of time, investigate the location and amount of the parasite on the snail, and conduct the trials in a more natural setting.