Dietary mercury and stress responses: how lifetime exposure to mercury alters stress responses and their relationship to spatial cognition

Abstract

Methylmercury is a widespread environmental contaminant that negatively impacts both humans and wildlife at sublethal levels. While environmental sources of methylmercury exist, the primary sources are anthropogenic, and most animals are exposed to methylmercury via diet. In my thesis, I examine how lifetime methylmercury exposure affects stress and cognition using the zebra finch model. My first goal is to examine the relationship between methylmercury and translocation stress. A captive colony of zebra finches from the College of William and Mary were transported to Auburn University. Two weeks before departure, birds were bled for baseline and stress-induced CORT. One day after arrival, birds were bled again in the same manner. Methylmercury exposed-birds experienced a significant increase in baseline CORT; however, methylmercury did not appear to impact stress-induced CORT. All birds experienced significantly lower stress-induced CORT as a result of translocation. My next goal is to examine how the interaction between methylmercury and CORT impacts spatial cognition. Zebra finches were put through a battery of spatial memory tests using baited wooden blocks with covers the birds were trained to remove. In general, the more stressed the bird, the longer it took to learn the procedure and the location of the food reward.