M. Albert, J. Straka, C. Harrison, M. Hove, C. Acidera, L. Lawson, D. Hornbach
Department of Biology, Macalester College, St. Paul, MN

During the life cycle of native freshwater mussels, they undergo a larval or glochidial period of parasitic encystment on fish or amphibian hosts. These
relationships play a vital role in the maintenance of mussel populations and in order to preserve the notable diversity and abundance of North America's freshwater
ecosystems, species-specific mussel-host relationships need to be more clearly defined. One of the major difficulties in clarifying these relationships in nature
involves identification of the microscopic juvenile forms, both as encysted glochidia and as successfully transformed juveniles. In this study, molecular techniques
are used in determining species-specific genetic markers. An intron in the genes encoding ribosomal RNA within the mussel genome, the ITS-1 region, was chosen
that was suspected to display interspecies polymorphism. This region is amplified using the Polymerase Chain Reaction (PCR). The amplified DNA is fragmented
with selected restriction endonucleases (REs), which cut the DNA at sequence specific sites. The amplified and cut DNA is analyzed by agarose gel
electrophoresis. If sequence polymorphism sensitive to the chosen REs appears within this region (Restriction Fragment Length Polymorphism, RFLP), unique
DNA fragmentation patterns are generated.

The goal of this RFLP analysis is the construction of a taxonomic key for the St. Croix River mussel populations that would allow species level identification of
glochidia or transformed juveniles. To date, RFLP patterns have been obtained for a total of 24 species. Distinguishing patterns for a number of species, including
members of the genus Quadrula, are reported.