Ptychobranchus fasciolaris
Kidney shell

Key Characteristics

The kidney shell is a medium to large (to 6 inches), elongate, and heavy mussel with a low and wide beak, straight to moderately curved ventral margin and well developed teeth. Shell is typically light in color, ranging from yellowish-tan to light brown, often with thick, broken green rays.  There is often a wrinkle on the inside surface of the shell.

Status and Rank

  • State Status: SC
  • State Rank: S2
  • Global Rank: G4G5


County NameNumber of OccurrencesYear Last Observed
St. Clair42011
Distribution map for Ptychobranchus fasciolaris

Updated 5/15/2018. 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 kidney shell occurs in high water quality creeks, rivers and lakes with moderate to swift currents and a sand or gravel substrate (Watters et al. 2009).

Specific Habitat Needs

needed in Mainstem Stream (3rd-4th order), Riffle, Mainstem Stream (3rd-4th order), Pool, Mainstem Stream (3rd-4th order), Run, River (5th-6th order), Riffle, River (5th-6th order), Pool, River (5th-6th order), Run, Inland Lake, Littoral, Benthic, Inland Lake, Pelagic, Benthic, Great Lake, Littoral, Benthic, Great Lake, Pelagic, Benthic

Natural Community Types


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.


The kidney shell experiences an especially high mortality rate in low dissolved oxygen conditions (Teztloff 2001). Limiting agricultural and urban runoff, wastewater treatment discharge, and other sources of point and non-point source pollution which contribute to such conditions will benefit this species. As zebra mussel infestation has lead to the extirpation of many native mussel communities, boat hulls and trailers, fishing gear and scuba equipment should be thoroughly cleaned before moving between waterbodies, in order to prevent the spread of zebra mussel larvae and adults. Construction projects such as bridge replacements and dam removals should plan for monitoring and mitigation measures to limit the impacts on mussel poplutions. A number of different fish species serve as hosts to Kidney shell glochidia. Healthy populations of host fish, as well as open water systems that allow for their movement,  must be maintained.

Active Period

Gravid from first week of August to fourth week of May

Survey Methods

Visual and tactile search using scuba or glass-bottom buckets. Tactile search (by hand) is especially important where water turbidity and pebbles/rocks make visual detection difficult. After identification, live mussels should be planted back into the substrate anterior end down. Surveys should not take place after heavy rains or during periods of high water as these conditions can make detection much more difficult.  Methods of documenting survey effort include: searching a large measured area, e.g. 128m2; taking multiple quadrat samples; and recording search time (person hours).  For all methods, at least some excavation of substrate (by hand, 5-10cm down) should be done to detect buried mussels.  Searching a large measured area or timed searches are generally better for detecting rare species and generating a species list than quadrat sampling.  These two methods allow more types of microhabitats and a larger area to be covered.  Quadrat sampling is better suited for documenting changes in density and other statistical analyses at the site level (Strayer and Smith 2003).

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Aug 17, 2018]


Survey References

Technical References

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