USE OF DNA BARCODING TO DETERMINE THE IDENTITY OF MUSSELS COLLECTED FROM NATURALLY INFESTED FRESHWATER DRUM FISH HOSTS

Nathan Juergens, Biology Department, Macalester College, 1600 Grand Avenue, St. Paul MN
Sarah L. Boyer, Biology Department, Macalester College, 1600 Grand Avenue, St. Paul MN
Mark C. Hove, Biology Department, Macalester College, 1600 Grand Avenue, St. Paul MN and Dept. of Fisheries, Wildlife and Conservation Biology, University of Minnesota, St. Paul MN

Many species of the Unionidae family of mussels have faced huge declines in numbers, with about 70% of the species listed as endangered, threatened or of special concern. They have a life cycle in which their larvae, called glochidia, parasitize fish by attaching to gills of the host. To inform conservation management decisions, understanding which mussels parasitize which fish and where is important. However, glochidia are extremely difficult to tell apart by morphology alone because of their small size and similarities in appearance between species.

DNA barcoding is a relatively new alternative to standard morphological identification. This approach uses a database of standardized mitochondrial DNA sequences. Sequences from new specimens can be compared back to the database for easy identification. During the Summer 2009 research season we sequenced DNA from frozen mussel samples available in the Biology Department at Macalester College, adding four Anodontoides ferussacianus sequences to an established database generated by our lab. We also did a detailed comparison of intra- and interspecific genetic distances for St. Croix mussel species.

We recovered glochidia from naturally parasitized freshwater drum in the St. Croix. To collect the fish specimens we went fishing several times in June 2009. Once we collected the fish we kept them in aquaria and allowed the juveniles to emerge naturally. We siphoned the bottoms of the tanks regularly to collect them. We sequenced the short mtDNA segments of the juveniles. The sequences from all of the juveniles were compared to the DNA barcoding database we had constructed. Using this method we were able to identify four juveniles from drum as Truncilla truncata and one juvenile as Potamilus ohiensis.