Assessing trematode infection patterns in aquatic ecosystems invaded by the faucet snail (bithynia tentaculata)

Abstract

Species introductions have profound impacts on global ecosystem dynamics leading to billions of dollars being spent on their control annually. Once introduced, invasive species can spread rapidly within their new environments via natural and anthropogenic means. Although more recent studies have begun investigating the mechanisms underlying the establishment and spread of invaders, there is still very little known about the factors dictating the success of invasive species in new environments. This knowledge gap becomes even more pronounced when invasive organisms are considered in conjunction with symbiotic species such as parasites. In 2002, the invasive faucet snail (Bithynia tentaculata) was discovered in the upper Mississippi River (UMR) and has been implicated in transmitting four novel parasite species to migrating waterfowl. Since the snail?s introduction, over 100,000 waterfowl have succumbed to trematodiasis during subsequent spring and fall migrations. In addition, new evidence suggests that the distribution of B. tentaculata has spread as far west as Georgetown Lake (Butte, MT) where waterfowl mortality has also been reported. The purpose of my thesis research was to address distinct questions regarding 1) the patterns of infection in B. tentaculata in two areas across the USA (Chapter I) and 2) the potential for B. tentaculata to interact with parasites native to one of the specific regions (the UMR) (Chapter II). To address the first question, field collections were performed at Georgetown Lake and the UMR to compare parasite populations residing in B. tentaculata. A deceased waterfowl was also collected from Georgetown Lake to compare infection patterns in definitive hosts to those found in B. tentaculata. The second question was addressed using both field and laboratory methods to assess the competency of B. tentaculata for the native digenetic trematode, Echinostoma revolutum. Results from Chapter I indicate the presence of one of the waterfowl-killing trematodes present in Georgetown Lake at a significantly higher mean intensity than those observed in B. tentaculata from the UMR. Chapter II reports B. tentaculata to be a competent host for the native parasite, Echinostoma revolutum. In addition, no difference in life history traits between B. tentaculata and a native snail (Physa gyrina) commonly serving as host for E. revolutum were observed. Together, the results from these two studies highlight the fact that broad spatial differences in the location of invasive species can equate to variability in the parasites found within these (as well as other) hosts. Furthermore, these results provide more insight into the ecological mechanisms determining the success of invasive species in new areas which may help to better predict the occurrence of waterfowl disease in areas where B. tentaculata and its parasites have the potential to occur. Research stemming from that reported in this thesis may uncover potential life cycle vulnerabilities in B. tentaculata and/or its parasites to attempt to alleviate waterfowl mortality in regions where it is found.