Infectious Diseases of Freshwater Mussels and Other Freshwater Bivalve Mollusks

Abstract

Numerous species of freshwater mussels (order Unionoida) are imperiled in the wild, and unionoids and other freshwater bivalves are important components of many ecosystems. Freshwater mussels also are propagated in captivity for production of pearls and enhancement of wild populations. However, infectious diseases of these mollusks have received relatively little attention. Unionidae is the most diverse family of freshwater bivalves, and most of the information available for this review is about species in this family. Eukaryotic organisms, especially trematodes, mites, and Conchophthirus spp. (Ciliata) are common inhabitants of unionids, and some have the potential to decrease the fitness of the host unionid. Several species of potentially pathogenic bacteria have been isolated from freshwater bivalves, but their role in diseases of bivalves has not been established. Evidence for viral diseases has been found in only one species of freshwater bivalve, a Chinese pearl mussel, Hyriopsis cumingii. The potential for some pathogens to cause greater harm to freshwater bivalves during periods of suboptimal conditions has not been evaluated adequately. Additional research is also needed to determine whether other types of pathogens are present in freshwater bivalves.

Keywords:

• unionoida
• viruses
• bacteria
• trematodes
• mites
• ciliates

ACKNOWLEDGMENTS

This project was funded by the State Wildlife Grants Program of the Alabama Department of Conservation and Natural Resources, Wildlife and Freshwater Fisheries Division. We thank Kellie Cosby for assistance with literature retrieval. The staff of the Auburn University Libraries provided assistance with document delivery and interlibrary loans.

Notes

¹Also known as postlarval resting stage I or nymphochrysalis.

²Also known as nymph.

³Also known as postlarval resting stage II, imagochrysalis, or teleiochrysalis.