Clams from the Dan River
Drs. Elizabeth Moore and Joe Keiper recently assisted with the identification of freshwater bivalves from the Dan River. These shells were collected by staff of the Dan River Basin Association after the February 3rd Duke Energy coal ash spill into the Dan River. DRBA is interested in the impact of the spill on the ecological health of the river and brought a sample of bivalve shells (the individuals were dead) from the river below the spill with some specific questions.
The first question DRBA asked us to address was, “Are these shells of the James River spinymussel (Pleurobema collina), which is a threatened species?” We used specimens in the VMNH Recent Invertebrate collection and some published reference guides to help us with this identification. The first step was to pull out the Pleurobema specimens in the collection and use those as a comparison to the unidentified shells. We do not have Pleurobema collina in the reference collection, but we do have specimens from the same genus but a different species, Pleurobema oviforme.
The unidentified shells look very different in morphology from the Pleurobema oviforme specimens so we feel confident that the sample from the Dan River are not the James River spinymussel.
Our next step was to look at two very useful references, “Freshwater Mussels of Alabama & the Mobile Basin in Georgia, Mississippi & Tennessee” and the “Workbook and Key to the Freshwater Bivalves of North Carolina.”
While the first volume doesn’t cover Virginia and North Carolina, there is considerable overlap in the species that occur in all of these states and the book has fantastic photos that are useful for aiding with identifications. These books led us to some likely candidates for identifying the Dan River shells so we went back to the VMNH collections. We found a pretty close match, marsh clams in the genus Corbicula.
The second question asked of us was whether we could tell if the clams died as a result of the coal ash spill. We could not. The soft tissue of the clam was not present but even if it was, we would have no way of determining their cause of death here at the museum. It may be possible for a lab to test for the presence of toxins or heavy metals but we do not have those types of facilities at VMNH. DRBA generously donated the Dan River specimens to VMNH and we will add them to our collections where they will be accessible for future research.
If you are interested in learning more about freshwater bivalves, a very useful web site is that for Dr. Art Bogan at the North Carolina Museum of Natural Sciences. A world renowned expert, Dr. Bogan has links to many online resources for learning more about freshwater bivalves.