Honors College

The Effects of Mercury Exposure on the Cytochrome C Oxidase I Gene of Larval Dragonflies

Megan Little, University of Maine


Mercury is an environmental pollutant; its most toxic form is methylmercury. Once mercury is converted to methylmercury in a body of water it is able to bioaccumulate in organisms and biomagnify up the food chain. Mercury is able to cause DNA damage through the generation of free radicals and binding to sulfhydryl groups of cysteines in zinc finger DNA binding domains, inhibiting DNA repair machinery. In this study the potential mutagenic effects of mercury were investigated on larval dragonflies (Odonta: Anisoptera) collected from national parks across the United States. Since mercury is a known mutagen it was hypothesized that the COI gene from dragonfly larvae collected from sites where they are subjected to higher mercury exposure should have more mutations than the COI gene from dragonfly larvae collected from sites where they are subjected to lower mercury concentrations. The COI gene from each sample was first used to determine species of selected dragonflies through DNA barcoding then was analyzed for mutations in its nucleotide and amino acid sequences. Samples showing mutations in their amino acid sequences were modeled to determine if the mutation caused a change in the protein structure. Mutations were detected that did change protein structure, but at this point it is unknown if this structural change impacts protein function. The mutation rate was ultimately shown not to increase at sites with greater mercury exposure. Instead, the data suggests that genetic variation in dragonflies decreases at higher concentrations of mercury.