Mussel of the

Page last updated
29 March 2007

Mussel of the Month

The April 2007 Mussel of the Month is Cyprogenia stegaria. Cyprogenia is an interesting Nearctic genus of two species: one from the Ozark Region west of the Mississippi, and the other from the Ohio Basin including the Cumberland Plateau.

Cyprogenia stegaria
Cincinnati, Ohio
(type of U. irroratus Lea, 1828 in the USNM).

Cyprogenia belongs to a group of freshwater mussels known as the lampsilines, which are endemic to North and Central America. Other lampsilines that have been featured as Mussel of the Month to-date include Lampsilis, Ptychobranchus, Hamiota, Potamilus and Ligumia. Among the characteristics that distinguish lampsilines from other freshwater mussels is the tendency to modify a portion of the ctenidia (gills) for brooding.

Typically the typical freshwater mussel life cycle involves parental care. Female mussels — rather than casting their gametes to the water to be fertilized externally like so many marine bivalvies — brood their ova and developing embryos in "marsupia" derived from modifications of their ctenidial demibranchs. In Cyprogenia, these modifications involve a large, coiled elaboration of the demibranchs. These elongate marsupial "tubes" serve the next stage in the freshwater mussel life cycle: parasitism upon freshwater fishes.

The spaces of the marsupium serve as molds for packaging the parasitic larvae. Cyprogenia larvae are packaged to look like elongate worms — a known favorite food of fish. The fish takes the bait and ends up facilitating the next generation of Cyprogenia! There are excellent pictures of the larvae of C. aberti (a closely related species) on Chris Barnhart's Unio Gallery.


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily UNIONOIDEA Rafinesque, 1820

Family UNIONIDAE s.s.
Subfamily AMBLEMINAE Rafinesque, 1820
Tribe LAMPSILINI von Ihering, 1901

Genus Cyprogenia Agassiz, 1852

Species Cyprogenia stegaria (Rafinesque, 1820)
(+ Unio irroratus Lea, 1828)

For more information about Cyprogenia, including recent taxonomic issues, check out:
  • Ortmann, A.E. 1912. Notes upon the families and genera of the Najades. Annals of the Carnegie Museum, 8: 222-365.
  • Parmalee, P.W. & A.E. Bogan. 1998. The freshwater mussels of Tennessee. University of Tennessee Press, Knoxville 328 pp.
  • Serb, J.M. 2006. Discovery of genetically distinct sympatric lineages in the freshwater mussel Cyprogenia aberti (Bivalia: Unionidae). Journal of Molluscan Studies, 72: 425-434.
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