The effects of dietary selenomethionine on the escape behaviours of Fathead Minnows

Abstract

Selenium is both an essential nutrient and a toxicant for animals, with only a relatively small concentration change separating the two. Toxicological work has reported various effects of selenium on fishes, including developmental impacts and deformities of the musculature and sensory systems. Behavioural ecotoxicology, a more sensitive study of toxicity, has also provided evidence that sublethal concentrations of selenium are having measurable impacts, such as negatively affecting swimming behaviours, in real-world ecosystems. In this thesis, I assessed the impacts of a selenomethionine-laden diet on the escape behaviours of the Fathead Minnow. Using kinematic analysis, I observed how fish responded to various looming threats. I exposed fish to sub-chronic periods of environmentally relevant concentrations of selenium in the form of selenomethionine-spiked diets. I achieved whole-body concentrations that approach Canadian tissue-specific guidelines for wild fish populations. In my first experiment, I used a weight drop to test the fish’s ability to respond to a mechanosenory stimulus and the performance of their fast-start response. My second experiment focused on the impacts of selenomethionine on visual acuity and how it affects visual perception of a threat. I also investigated how exposed fish would recover from any potential impacts when returned to a contaminant-free diet. My results indicated there was no significant effect of selenomethionine on either the visual response to a threat, or burst swimming behaviours of the fast-start response in Fathead Minnows. Additionally, there were no latent changes to Fathead Minnow escape behaviour throughout the recovery period. These results were contrary to both my predictions and the literature that showed critical swimming behaviour was compromised in selenomethionine -exposed freshwater fish. My work helps to show that the effects of toxicants on behaviours can be highly specific and cannot be generalized.