Hove, M.C. and A.R. Kapuscinski. 1998. Ecological relationships between six rare Minnesota mussels and their host fishes. Final report to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 17 pp.
Of 297 freshwater mussel species living in North America, 213 are either endangered, threatened, or of special concern. The identification of fish hosts is listed as an urgent research objective in the National Strategy for Freshwater Mussel Conservation. Suitable hosts were determined by artificially infesting various fishes and amphibians with glochidia from one of six mussel species. A fish was considered a suitable host when larval metamorphosis to the juvenile stage was observed. Although twenty-five fish species and mudpuppy were exposed to spectaclecase glochidia, none of the species tested facilitated glochidial metamorphosis. Three-fold shell growth was observed on pistolgrip juveniles collected from yellow and brown bullheads. Transformation of ellipse glochidia was observed in mottled sculpin, four darters, and brook stickleback. Metamorphosis of butterfly glochidia was not observed. Blackside darter and logperch were found to be suitable hosts for snuffbox. Purple wartyback glochidia transformed on four catfishes.
We used microscopy and initiated molecular techniques to identify a subsample of approximately 5000 juvenile mussels collected from freshwater drum naturally infested with glochidia. Light microscopes and a scanning electron microscope were used to study the juvenile mussels and glochidia from mussels whose length is less than 100 ?m. Species identification was limited to subfamily using light microscopes. Analysis of shell surface sculpture, shell outline, and shell height from scanning electron micrographs suggest the subsample of juveniles are either Truncilla truncata or T. donaciformis. We verified the use of published molecular markers for identifying mussel species but specific markers for St. Croix River mussels that release glochidia under 100 ?m in length are still under development. Studies were initiated to determine if some mussels produce chemical cues to attract host fishes. Improved understanding of glochidial host requirements and ecological relationships between mussels and their hosts will help managers determine the viability of imperiled mussel populations.