Effects of digenetic trematodes on Physa gyrina morphology and movement.

Abstract

The purpose of this study was to investigate how parasites modify the behavior of their hosts in order to facilitate transmission. We looked at the freshwater snail, Physa gyrina parasitized by a digenetic trematode that uses the snail as its first intermediate host. We asked whether or not parasites alter the size of a snail, whether parasites alter the amount movement of a snail, and the speed at which a snail travels. Time trials were run in an aquarium with a three-dimensioinal coordinate system to track snail movement. We found that parasites do not affect snail size, but do slow the movement of a snail as well as causing them to move less distance when compared to uninfected snails. This study shows that digenetic trematodes affect the movement of snails, but it failed to show a relationship between parasite load and snail size.