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4 October 2004 |
Mussel of the Month
The October 2004 Mussel of the Month is Margaritifera (+ Cumberlandia) monodonta. M. monodonta, a North American species, is one of only about a dozen in the family Margaritiferidae.
[This species has been re-reclassified back to the genus Cumberlandia — DLG.]
ANSP 358640. Clinch River, Evans Knob, Hancock County.
17 November 1978, S. Ahlstedt!
The Margaritiferidae is composed of around a dozen species, depending on who you ask. The Russian School of malacology recognizes as many as 16 valid taxa. Most authorities agree that there are five species in North America, one of which is M. monodona. The rest are found dispersed throughout the northern hemisphere of the Old World.
The traditional consensus has been that margaritiferids are "primitive" based upon the numerous traits they share with Neotrigonia, the closest living marine ancestor of freshwater mussels. For example, among margaritiferids, the ctenidia are not fused along their entire length to the adjacent mantle and the brooding demibranchs are not organized into a series of vertical water-tubes (among other characteristics). However, recent molecular phylogenetic studies have found Margaritifera to be more derived than previously though. Perhaps the presumably "primitive" condition actually represents a loss of certain characters shared by the rest of the freshwater mussels.
Classification:
Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida
Superfamily Unionoidea Rafinesque, 1820
Family Margaritiferidae Haas, 1940
Genus Margaritifera Schumacher, 1816
+ Cumberlandia Ortmann, 1912
Species Margaritifera monodonta (Say, 1829)
For more information about Margaritifera monodonta and the Margaritiferidae, check out the following:
- Chris Barnhart has pictures of the various life history stages of M. monodonta on his Unio Gallery website.
- Smith, D.G. 2001. Systematics and distribution of the recent Margaritiferidae. pp. 33-49. [In] G. Bauer & K. Wächtler (eds.). Ecology and Evolution of the Freshwater Mussels Unionoida. Ecological Studies Vol. 145, Springer-Verlag, Berlin. 394 pp.
- Huff, S.W., D. Campbell, D.L. Gustafson, C. Lydeard, C.R. Altaba & G. Giribet. 2004. Investigations into the phylogenetic relationships of freshwater pearl mussels (Bivalvia: Margaritiferidae) based on molecular data: implications for their taxonomy and biogeography. Journal of Molluscan Studies 70: 379-388.
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