Plants and Animals

Lasmigona costata Flutedshell

species photo
Peter Badra
species photo
Kurt Stepnitz
species photo
Kurt Stepnitz
species photo
Peter Badra
species photo
Peter Badra
species photo
Peter Badra
species photo
Peter Badra
species photo
Peter Badra

Key Characteristics

The flutedshell has a distinct washboard, or fluted, texture to its shell on the posterior-dorsal slope. The fluted texture is often hidden by algae, caddisfly larvae, and/or marl since the posterior end of the shell extends up out of the stream bottom into the water column. Maximum length is 15 cm and the mussel’s life span is around 20 years. Flutedshell has a wedged shaped outline at the posterior end with the posterior point of the shell far to the ventral side, and an elliptical outline at the anterior end. It is relatively compressed. Beak sculpture consists of two to four ridges, sometime slightly ‘W’ shaped. The beak is not inflated, and the beak cavity is shallow. Color ranges from yellow to tan to green in young individuals and is usually dark brown for individuals older than five or six years of age.  Flutedshell has numerous green or brown rays that become obscured as the shell darkens with age. The cardinal and lateral teeth are weakly developed, with the lateral tooth being a thickening along the hinge line rather than a well-developed tongue and grove articulation. The nacre is usually white, sometimes with some salmon coloring.   

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: SNR - Not ranked


CountyNumber of OccurrencesYear Last Observed
Alger 2 2018
Allegan 13 2019
Alpena 3 1971
Antrim 1 Historical
Barry 3 2012
Benzie 2 1949
Berrien 5 2001
Branch 1 1942
Calhoun 13 2019
Cass 1 2019
Cheboygan 1 2018
Chippewa 1 1935
Clare 1 1938
Clinton 9 2021
Crawford 1 1934
Dickinson 8 2009
Eaton 10 2016
Genesee 1 2008
Grand Traverse 2 1949
Gratiot 4 2019
Hillsdale 6 2005
Huron 1 1908
Ingham 4 2015
Ionia 30 2021
Isabella 7 2020
Jackson 7 2018
Kalamazoo 15 2019
Kent 15 2022
Lake 1 Historical
Lapeer 2 1926
Leelanau 1 1928
Lenawee 3 1934
Livingston 3 2018
Luce 1 1935
Mackinac 2 2019
Macomb 7 2011
Mecosta 6 2022
Menominee 3 2009
Midland 5 2020
Monroe 8 2020
Montcalm 8 2015
Montmorency 1 1944
Newaygo 3 1949
Oakland 1 Historical
Oceana 2 2012
Osceola 2 2018
Ottawa 2 1960
Presque Isle 3 1959
Roscommon 1 1934
Saginaw 6 2011
Sanilac 3 2019
Schoolcraft 1 2019
Shiawassee 1 1926
St. Clair 21 2020
St. Joseph 16 2019
Tuscola 10 2019
Van Buren 6 2022
Washtenaw 3 1943
Wayne 15 2020

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


The flutedshell is found in small and medium rivers, and in Lake St. Clair and Lake Erie. They are often found in sandy mud and cobble substrates.

Natural Community Types

  • Great lake, littoral, benthic
  • Inland lake, littoral, benthic
  • Mainstem stream (3rd-4th order), pool
  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle
  • River (5th-6th order), pool
  • River (5th-6th order), run
  • River (5th-6th order), riffle

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

The flutedshell is being impacted by point source pollution, non-point source pollution, alteration of natural stream flow patterns, barriers to host fish passage, direct alteration of habitat, and invasive zebra mussels.

Limit or eliminate point source discharges of ammonia, chloride, sulfate, heavy metals, and other substances toxic to native mussels. Avoid use of aquatic herbicides containing copper. Maintain riparian buffers along streams and promote land conservation programs to help reduce excessive erosion, sedimentation, and nutrient input from non-point sources. Maintain integrity of headwater streams and wetlands, which support the ecological function of downstream river habitats. Improve passage for fish by removing unnecessary dams and upgrading poor stream/road crossings such as culverts that are too small or are perched. Flutedshell and other native mussels require fish hosts to complete their life cycle and rely on fish passage to travel to new habitats and facilitate gene flow among mussel populations. Avoid dredging, channelization, and other in-stream impacts whenever possible.

The spread of zebra mussels into Michigan’s streams and lakes remains a serious threat throughout the flutedshell’s range. Reduce the impact of zebra mussels by avoiding the transport of water or aquatic plants – which can contain zebra mussel larvae – from one body of water to another while boating, fishing, hunting, and researching. Washing boats, trailers, and gear, and letting them dry overnight reduces the potential for spreading zebra mussels.

Active Period

Gravid from first week of August to fourth week of August

Survey Methods

In water shallower than waist deep, wading with a glass bottom bucket and, if water quality is good, swimming with a snorkel and mask are effective ways to observe flutedshell. SCUBA or other dive gear is required for greater water depths. River and lake substrate should be searched both visually and tactilely, by sweeping the fingers through the substrate. Though flutedshell are typically found at least partly exposed to the water column, they can be completely buried at times and difficult to detect visually. Empty shells may be found along riverbanks and occasionally in shell middens created by predators such as muskrats.

A scientific collector’s permit is required to possess live native mussels shell or live individuals. Mussel surveys related to permitted projects in rivers and lakes should follow the Michigan Freshwater Mussel Survey Protocols and Relocation Procedures. Federal and/or state threatened and endangered species permits must be obtained prior to surveying for native mussels within waterbodies likely to support these species. Refer to the Mussel Map Viewer available on MNFI’s website.

Glass-bottom bucket less than waist deep water

Survey Period: From first week of June to first week of October

SCUBA greater than waist deep water

Survey Period: From first week of June to first week of October

Survey Method Comment: Surface supplied diving may be appropriate in some cases.

Snorkeling searches

Survey Period: From first week of June to first week of October

Survey Method Comment: Use this method only when water quality and conditions are safe for swimming.


Survey References

  • Hanshue, S., J. Rathbun, P. Badra, J. Bettaso, B. Hosler, J. Pruden, and J. Grabarkiewicz. 2019. Michigan Freshwater Mussel Survey Protocols and Relocation Procedures [for rivers], Version 2. Michigan Department of Natural Resources.
  • Metcalfe-Smith, J., A. MacKenzie, I. Carmichael, and D. McGoldrick. 2005. Photo Field Guide to the Freshwater Mussels of Ontario. St. Thomas Field Naturalist Club Inc, 60 pp.
  • Mulcrone, R.S., and J.E. Rathbun. 2018. Field Guide to the Freshwater Mussels of Michigan.  Michigan Department of Natural Resources, 59 pp.
  • Watters, G. Thomas, Michael A. Hoggarth, and David H. Stansbery. 2009. The Freshwater Mussels of Ohio. The Ohio State University Press, Columbus. 421 pp.

Technical References

  • Blevins, E., L. McMullen, S. Jepsen, M. Blackburn., A. Code, and S.H. Black. 2017. Conserving the Gems of Our Waters: Best Management Practices for Protecting Native Western Freshwater Mussels During Aquatic and Riparian Restoration, Construction, and Land Management Projects and Activities. 108 pp. Portland, OR: The Xerces Society for Invertebrate Conservation.
  • Brim-Box, J., and J. Mossa. 1999. Sediment, land use, and freshwater mussels: Prospects and problems. Journal of the North American Benthological Society 18: 99-117.
  • Colvin, S.A.R., S.M.P. Sullivan, P.D. Shirey, R.W. Colvin, K.O. Winemiller, R.M. Hughes, K.D. Fausch, D.M. Infante, J.D. Olden, K.R. Bestgen, R.J. Danehy, and L. Eby. 2019. Headwater streams and wetlands are critical for sustaining fish, fisheries, and ecosystem services. American Fisheries Society Special Report. Fisheries 44: 73-91.
  • Freshwater Mollusk Conservation Society. 2016. A national strategy for the conservation of native freshwater mollusks. Freshwater Mollusk Biology and Conservation 19: 1-21.
  • Haag, W.R. 2012. North American Freshwater Mussels: Natural History, Ecology, and Conservation. Cambridge University Press, New York, 505 pp.
  • Strayer, D.L. and D.R. Smith. 2003. A Guide to Sampling Freshwater Mussel Populations. American Fisheries Society Monograph 8, Bethesda. 103pp.
  • Watters, G.T. 1996. Small dams as barriers to freshwater mussels (Bivalvia, Unionoida) and their hosts. Biological Conservation 75: 79-85.