Correlating incidences of Dreissena polymorpha colonization with trematode larvae infection in Stagnicola emarginata snails.

Abstract

The invasive zebra mussel (Dreissena polymorpha), has negatively impacted many northern Michigan aquatic species in the past 20 years (Strayer, 2009). One of the species affected has been Stagnicola emerginata, a freshwater snail. This species of snail also acts as the intermediate host for the larvae of a number of trematode species which increase the size of the snail, possibly making them more vulnerable to zebra mussel colonization (Horak and Adema, 2002).The purpose of this study was the determination of a correlation between schistosome parasitism, and Dreissena polymorpha colonization on Stagnicola emerginata. Over 2000 snails were collected from Burt Lake MI, and where individually examined for cercarial emergence using fluorescent lighting to induce shedding. Rates of schistosome parasitism were correlated with presence or absence of D. polymorpha on each specimen. Based upon the analysis of these data, it has been concluded that no link, positive or negative, between schistosome parasitism and D. polymorpha colonization on the snails may be supported. The lack of negative effects on the S. emerginata seems to indicate prudent parasitism by the larvae.