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1 April 2013 |
Mussel of the Month
The April 2013 Mussel of the Month is Corbicula fluminea. Corbicula is a genus of freshwater bivalves in the family Cyrenidae that could have as many as 90 valid species. The genus has been widely introduced but its native range covers Africa and much of Asia.
ANSP 416332. Sangamon River, Lake of the Woods, Mahomet, Champaign Co., Illinois.
Cummings, Graf & Tiemann! 2007.
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Corbicula is not a freshwater mussel. We know that. But it is still an interesting freshwater bivalve. Moreover, 1 April provides an opportunity to whoop it up and think outside the box for a bit. Corbicula is well known as an invasive freshwater bivalve worldwide, including North America. Compared to other freshwater bivalves, the genus is distinctive for lots of reasons, not the least of which is the prevalence of androgenetic reproduction (Hedtke et al., 2011). For this non-mussel Mussel of the Month, we will focus on our evolving understanding of the species-diversity of the genus.
Beginning in the late 1970s, it was hypothesized that there were only two species of Corbicula on Earth. All freshwater species were considered C. fluminea, and the brackish populations were classified as C. fluminalis (Morton, 1979, 1986). That paradigm definitely simplified classification of the North American invasive species: C. fluminea. The two-species hypothesis was supported by the finding that the allozymes of putative Corbicula species in Thailand were little diversified (Kijviriya et al., 1991).
However, other data suggest a greater species richness for Corbicula:
- diagnostic allozymes and morphological characters among invasive Corbicula populations in North America (Hillis and Patton, 1982),
- distinct mitochondrial haplotypes among North American invasive Corbicula corresponding to those morphotypes (Lee et al., 2005),
- distinct mitochondrial haplotypes for a number of sexual and asexual nominal species throughout the native range of the genus (Glaubrecht et al., 2003),
- and, a great deal of conchological variation.
This is just a sample of the conchological diversity of the genus Corbicula.
The collapse of the predominant taxonomic theory for Corbicula leaves us in a bit of an information vacuum. Our current list for the genus Corbicula relies by necessity on dated and provincial revisions too numerous to cite here. We suspect that our current tally of 89 Recent species will change as more information becomes available. But, whether the number will go up or down, we aren't really sure. |
To find out more about Corbicula and the diversity of the group, check out:
- Glaubrecht, M., T. von Rintelen, & A.V. Korniushin. 2003. Toward a systematic revision of brooding freshwater Corbiculidae in southeast Asia (Bivalvia: Veneroida): on shell morphology, anatomy and molecular phylogenetics of endemic taxa from islands in Indonesia. Malacologia 45: 1-40.
- Hedtke, S.M., M. Glaubrecht, & D.M. Hillis. 2011. Rare gene capture in predominantly androgenetic species. Proceedings of the National Academy of Sciences 108: 9520-9524.
- Hillis, D.M. & J.C. Patton. 1982. Morphological and electrophoretic evidence for two species of Corbicula (Bivalvia: Corbiculidae) in North America. American Midland Naturalist 108: 74-80.
- Kijviriya, V., E. S. Upatham, V. Viyanant, & D. S. Woodruff. 1991. Genetic studies of the Asiatic clams, Corbicula, in Thailand: allozymes of 21 nominal species are identical. American Malacological Bulletin 8:97-106.
- Lee, T., S. Siripattrawan, C.F. Ituarte, & D. Ó Foighil. 2005. Invasion of the clonal clams: Corbicula lineages in the New World. American Malacological Bulletin 20: 113-122.
- Morton, B.S. 1979. Corbicula in Asia. [in] J.C. Britton, ed. Proceedings of the First International Corbicula Symposium, Texas Christian University, Fort Worth, Texas, October 13-15. Texas Christian University Research Foundation, Fort Worth.
- Morton, B.S. 1986. Corbicula in Asia — un updated synthesis. American Malacological Bulletin, Special Edition 2: 113-124.
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