AIM

Montana Bivalvia List Summary

The freshwater mussels (family Unionidae) must now be fairly well known. Only 5 species are known for sure in Montana. The Freshwater fingernail clams (family Sphaeriidae) are poorly known here. The currently list is mostly the widespread North America species. Their status in Montana requires much more collecting and study.

Recent Discoveries

Collections from 1996 added a few new mussel locations, but no new state records. The most interesting discovery is the headwater population of Lampsilis siliquoidea in the lower Jefferson River. This likely represent a fairly recent range expansion for this species. They were most likely carried on some introduced fish. Most of the fish in this part of the river are introduced.

Research Needs

All of our mussel species are at the headwaters of their range- even their basic biology has not yet been examined here. I have hypothesized that 2 species, Lasmigona complanata and Ligumia recta might be recent additions to the state- this should be examined better. A genetic study of Margaritifera falcata across the continental divide area may help explain the colonization of the Missouri River headwaters by westslope cutthroat trout.

Acknowledgments

  • Kevin Cummings (Illinois Natural History Survey) identified some Montana mussels and reviewed the early editions of all unionid pages.
  • Fred Thompson (Florida State Museum) has identified some Montana bivalves.
  • Howard Johnson (Montana Fish Wildlife and Parks) provided Montana specimens.
  • Jim Reichel (Montana Natural Heritage Program) provided Montana specimens.
  • Mike Ruggles (Montana Fish Wildlife and Parks) provided Montana specimens

Some Name Changes

15 APR 1996, Updated on 7 FEB 1997 D.L. Gustafson