Spectacle case pearly mussel

Spectacle case pearly mussel


Cumberlandia monodonta

Cumberlandia monodonta (common name spectaclecase) is a freshwater mussel endemic to the United States. Currently, C. monodonta is listed as an endangered species by the U.S. Fish and Wildlife Service and the International Union for Conservation of Nature.

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Cumberlandia monodonta was first reported in a newspaper titled The Disseminator (New Harmony, Ind.) by Thomas Say in 1829 under the name Unio monodonta. The spectaclecase was then reclassified into the genus Cumberlandia by A. E. Ortmann in 1912.

Cumberlandia monodonta has experienced a drastic decline in population due to human activity, resulting in its listing as "Endangered" by the Endangered Species Act and the IUCN. In particular, the construction of dams has caused significant problems that disrupt C. monodonta 's habitat and food supply. The Endangered Species Act classifies C. monodonta as a highly threatened species with a low potential for recovery.

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Cumberlandia monodonta have oblong shells that grow at least 9.25 inches. The shell’s texture is primarily smooth and will crack along the posterior end when dry. Younger C. monodonta shells appear a light yellowish-green but darken to a brown or black in older specimens.



Cumberlandia monodonta is endemic to the Mississippi, Ohio, and Missouri River basins and is found most often in larger rivers. They are most commonly found in aggregated clumps within mild water, between large rocks and wedged into firm mud. C. monodonta take shelter from the current by clustering beneath slab boulders or bedrock shelves.

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Historically, C. monodonta has occurred in at least 44 streams within its three endemic basins. As of 2014, the mussel was known to occupy only 20 streams, representing a 55% decline in range. Furthermore, these populations are highly fragmented and cover only short stretches of a given river. The mussel’s 5-Year Review reports that there has been no change in C. monodonta ’s range since its listing as Endangered. C. monodonta does not reside in any critical habitat. A map of C. monodonta 's historical and present range can be found on its IUCN Red List web page.

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Diet and Nutrition

Adult C. monodonta will bury themselves under the river's substrate and filter feed, with a diet consisting of algae, bacteria, and dissolved organic material.


1. Spectacle case pearly mussel Wikipedia article - https://en.wikipedia.org/wiki/Spectacle_case_pearly_mussel
2. Spectacle case pearly mussel on The IUCN Red List site - https://www.iucnredlist.org/species/5952/3078239

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