We report the first results of a parasitological study of Dreissena polymorpha (zebra mussels) from the brackish Curonian Lagoon, SE Baltic Sea. Zebra mussels were collected monthly from May to October 2011 from a site near the mouth of the River Nemunas. Three types of endosymbionts were found in the mantle cavity and visceral mass of the molluscs during dissections, i.e. the commensal ciliate Conchophthirus acuminatus and parasitic ciliate Ophryoglena sp., and rarely encountered, unidentified nematodes. The abundances of C. acuminatus and Ophryoglena sp. were positively associated with host shell length and water temperature, but no effect of water salinity was detected. As the endosymbionts are either highly host-specific to zebra mussels (C. acuminatus and Ophryoglena sp.) or are probably free-living organisms that inadvertently infect the molluscs (nematodes), we conclude that the presence of D. polymorpha in the Curonian Lagoon does not pose any serious parasitological risk to native biota.We emphasize, however, that this conclusion should be treated with caution as it is based on a study conducted only at a single location. Our work extends the currently scarce records of D. polymorpha parasites and commensals from brackish waters, and adds to a better understanding of the ecological impact this highly invasive mollusc causes in the areas it has invaded.
Oceanologia 54(4): 701-713

We report the results of a two-year study in the Svisloch River (Minsk, Belarus) on the dynamics of infection in Dreissena polymorpha by nematodes and three ciliate species Conchophthirus acuminatus, Ophryoglena sp., and Ancistrumina limnica. Although these endosymbionts were present in most of the samples, their prevalence and infection intensity differed significantly. C. acuminatus and A. limnica infection intensities in both years of the study had a maximum in summer and were positively correlated with water temperature. In contrast, Ophryoglena sp. and nematode infection intensities were considerably lower in summer versus winter and were negatively correlated with temperature. In the first long-term study to monitor the size and reproductive rate of C. acuminatus, we found that mean length was negatively correlated with temperature and that temperature was positively correlated with asexual reproduction, with a peak of cell division in April as water temperatures increased.
Journal of Invertebrate Pathology (2003) Volume 83: 73–82