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6 December 2023

Mussel of the Month

The December 2023 Mussel of the Month is Fusconaia cor. Fusconaia is a genus of 14 species from eastern North America.

This month is the 50th anniversary of the Endangered Species Act in the U.S.A., so it is appropriate to focus on an endangered species that is benefiting from that historic legislation. Fusconaia cor, endemic to the Tennessee River basin in Alabama, Tennessee, and Virginia, is listed as endangered according to the U.S. Fish & Wildlife Service. It is listed as critically endangered on the IUCN Red List. A recent 5-year review nicely summarizes the current state of affairs for Fusconaia cor. Another reason to highlight Fusconaia cor is to revisit the taxonomy of the genus Fusconaia. The chart below summarizes the gist of the revisions to the classifications of the species traditionally assigned to Fusconaia. Our first checklist (Graf & Cummings, 2007) was based mostly on the late 20th century taxonomy since Burch (1975), and the then-current conception of Fusconaia was a mix of species that had previously been assigned to other genera like Pleuronaia, Elliptio, and Obovaria (Frierson, 1927; Haas, 1969). All of the red-bodied mussel species brooding their larvae in all four demibranchs were grouped in Fusconaia — or at least the mussels assumed to be red-bodied and tetragenous based on the similarity of their shells to mussels known to have those soft-body traits. In the cladistic era, the traditional Fusconaia has acquired more species from now-defunct genera like Quincuncina and Lexingtonia, and other species have been exported to genera like Pleuronaia, Pleurobema, Pustulosa, and Reginaia (Campbell et al., 2005; Williams et al., 2008; Campbell & Lydeard, 2012). The latter two genera are classified in different tribes from each other and from Fusconaia! The available phylogenetic data are summarized on the Pleurobemini Cladomics page. Things seems to have stabilized with Fusconaia — at least for the time being.

To find out more about the classification of Fusconaia and related genera, check out:

• Burch, J.B. 1975. Freshwater Unionacean clams (Mollusca: Pelecypoda) of North America.  [Revised Edition]. Malacological Publications. Hamburg, Michigan. 204 pp.
• Campbell, D.C., J.M. Serb, J.E. Buhay, K.J. Roe, R.L. Minton & C. Lydeard. 2005. Phylogeny of North American amblemines (Bivalvia, Unionidae): prodigious polyphyly proves pervasive across genera. Invertebrate Biology 124(2): 131-164.
• Campbell, D.C. & C. Lydeard. 2012. Molecular systematics of Fusconaia (Bivalvia: Unionidae: Ambleminae). American Malacological Bulletin 30(1): 1-17.
• Frierson, L.S. 1927. A classification and annotated check list of the North American naiades. Baylor University Press, Waco, Texas. 111 pp.
• Graf, D.L. & K.S. Cummings. 2007. Review of the systematics and global diversity of freshwater mussel species (Bivalvia: Unionoida). Journal of Molluscan Studies 73: 291-314.
• Graf, D.L. & K.S. Cummings. 2021. A ‘big data’ approach to global freshwater mussel diversity (Bivalvia: Unionoida), with an updated checklist of genera and species. Journal of Molluscan Studies 87(1). eyaa034 (36 pp.).
• Haas, F. 1969. Superfamilia Unionacea. Das Tierreich 88. Walter de Gruyter and Co., Berlin. 663 pp.
• Parmalee, P.W. & A.E. Bogan. 1998. The freshwater mussels of Tennessee. University of Tennessee Press, Knoxville. 328 pp.
• Williams, J.D., M.L. Warren, K.S. Cummings, J.L. Harris & R.J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.
• Williams, J.D., A.E. Bogan & J.T. Garner. 2008. Freshwater Mussels of Alabama and the Mobile Basin in Georgia, Mississippi and Tennessee. University of Alabama Press, Tuscaloosa. 908 pp.
• Williams, J.D., A.E. Bogan, R.S. Butler, K.S. Cummings, J.T. Garner et al. 2017. A revised checklist of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20(2): 33-58.