Meeting Abstract
Environmental contamination is a growing global concern, and amphibian susceptibility to contaminants varies both within and among populations. In previous work we found evidence of amphibian population adaptation to contaminated environments, however we did not explore the mechanisms and associated costs of this tolerance. DNA methylation is an epigenetic mechanism with important gene expression regulatory function in many animals and can vary with contaminant exposure. Additionally, increased global methylation patterns can contribute to accelerated aging rates and may represent a cost of contaminant exposure and/or tolerance. Our objectives were to 1) measure global DNA methylation in amphibians experimentally exposed an environmentally relevant trace element, 2) quantify variation in global DNA methylation across amphibian populations from wetlands differing trace element levels. To accomplish objective one, we exposed larvae of two species, Anaxyrus terrestris and Gastrophryne carolinensis, from populations with different exposure histories, to copper [Cu] and measured whole body global DNA methylation. A. terrestris larvae exhibited a negative relationship between methylation and increasing Cu exposure, regardless of exposure history. G. carolinensis larvae with no population history of exposure exhibited a similar pattern. However, larvae from contaminant exposed populations showed hypermethylation with Cu exposure. To accomplish objective two, we collected Lithobates sphenosephalus and A. terrestris eggs, larvae, and adults from wetlands differing in contamination type and level, and measured global DNA methylation in whole embryos, liver and brain. Broadly, DNA methylation levels increased with age, and patterns differed among species, tissue type, and wetland contamination history.
