Helminth and protist parasites of zebra mussels, Dreissena polymorpha (Pallas, 1771), in the Great Lakes region of southwestern Ontario, with comments on associated bacteria

Abstract

Zebra mussels (Dreissena polymorpha) collected in June 1991 from three localities in the Great Lakes region of south-western Ontario were examined for helminth and protist parasites. In addition, the bacteria in both live and dead mussels were identified and the effects of Serratia liquefaciens and Escherichia coli on D. polymorpha were monitored experimentally. Helminths were not found in mussels from the Puce site (Lake St. Clair); the prevalence of plagiorchiid metacercariae in mussels from Port Colborne (Lake Erie) was 2.9% and of aspidogastrids (adults and juveniles of Aspidogaster conchicola) in mussels from Leamington (Lake Erie), 2.7%. These findings represent locality records and a new host record for the digenean. The ciliate Ophryoglena sp. was found in mussels from Puce (prevalence 1.3%), Port Colborne (prevalence 4.3%), and Leamington (prevalence 2.7%). The principal bacteria found in both living and dead mussels were Aeromonas sp., Pseudomonas sp., and Bacillus sp. Both high and low concentrations of S. liquefaciens that were tested were lethal to mussels, while similar concentrations of E. coli produced no effects. Both bacteria are recognized as being opportunistic pathogens in many organisms. These preliminary findings suggest that helminths will not play a major role in the control of zebra mussels. However, the potentially pathogenic ciliate protists and bacteria warrant further investigation.