Effects of desiccation on two life stages of an invasive snail and its native cohabitant

Abstract

Invasive species are of critical concern as they have the potential to rapidly alter biotic systems around the globe. The upper Mississippi River (UMR) system has been recently invaded by the aquatic snail, Bithynia tentaculata, which spread from the Great Lakes region. In addition to potentially impacting native aquatic snails, B. tentaculata also carries three parasites which kill thousands of migrating waterfowl annually. Although this invader is having detrimental impacts on a number of species in the UMR region, little is known regarding (1) the tolerances of B. tentaculata to abiotic stresses in this area, and (2) how stress thresholds in this species compare to native species across developmental stages. To help fill in these informational gaps, we conducted a series of laboratory experiments aimed at assessing the tolerances of B. tentaculata and a native snail (Physa gyrina) to desiccation at two stages of ontogeny (eggs and adults). Results showed that P. gyrina egg masses were more tolerant to a transient desiccation period (9 h) than B. tentaculata egg masses as evidenced by their higher hatching success. Conversely, adult survival in B. tentaculata was much greater than that of P. gyrina after a longer desiccation period (1 week). Although superior tolerance to drying varies between the developmental stages of each species, B. tentaculata may have an overall advantage due to its ability to endure prolonged drying at maturity. These results suggest that hydrologic fluctuations in the UMR may contribute to reductions in P. gyrina numbers, potentially facilitating B. tentaculata colonization and the spread of waterfowl infections.