The freshwater mussel family Unionidae is represented by at least 269 recent species in the Southeast. Throughout southeastern states the harvest of unionids for raw shell used in the cultured pearl industry represents at least a 25 million dollar per year enterprise. Unfortunately, over the past several decades many factors have contributed to imperil many mussel species and today at least 71% of the North American unionid fauna is considered endangered, threatened, or otherwise in need of special concern. Efforts to save this valuable natural resource have included studies aimed at gathering life history information needed to best manage mussels as well as research to evaluate the use of aquaculture to propagate mussels for reintroduction. As part of these studies, the Tennessee Aquarium and University of Connecticut have collaborated with the Tennessee Wildlife Resources Agency to investigate the metazoan symbiont fauna of mussels living in Kentucky Lake.

As of the fall of 1995, a total of 346 unionid mussels comprising eight species have been examined for metazoan symbionts. Mussels were collected between the 87.4 and 197.6 mile markers of the Tennessee River between May 1994 and June 1995. A total of 1685 metazoan symbionts representing six phyla, 12 families, and at least 13 genera and species were identified from sampled mussels. Free-living commensals accounted for only 9.3% of all collected symbionts and were represented by nematodes, insects, an annelid and a tartigrade. Parasite taxa belonging to the Aspidogasteridae and Unionicolidae accounted for over 99% of all collected parasites, and only two members of these families achieved prevalence values greater than 10%. Occurrences of the three major symbiotic taxa (unionicolids, aspidogastrids, and dorylaimids) were statistically determined to be unrelated events even though individual mussels were found to be inhabited by varying combinations of up to all three of these taxa. The platyhelminth Aspidogaster conchicola exhibited an over-dispersed distribution within one sample of Quadrula quadrula, while the mite Unionicola vikira exhibited a random distribution within the same sample. Preliminary results of this study along with those of previous researchers suggest that unionids appear to be insulted by a relatively impoverished metazoan parasite fauna (regarding number of parasite species) as compared to other host taxa of similar species richness. The evolutionary and ecological implications of this could be significant and are worth pursuing via continued research.

*This project represents work completed to date under Tennessee Wildlife Resources Agency contract No. 7A-4-l 1062-4-00. Copies of annual project reports are available upon request from: G.W. Benz, Tennessee Aquarium, One Broad St., P.O. Box 11048, Chattanooga, TN 37401.