Effects of copper on the acute ventilatory drive of killifish, Fundulus heteroclitus

Abstract

Organisms are often exposed to multiple stressors in their natural habitat. While the effects of individual stressors alone are generally well-studied, their combined interactions are often unknown. One such unknown interaction is that between copper, an essential micronutrient that is toxic in high levels, and hypoxia, a commonly experienced environmental stressor. This project sought to examine the effects that copper has on the hypoxic response as well as the combined effects of copper and hypoxia exposure using freshwater-acclimated adult killifish (Fundulus heteroclitus), a model euryhaline teleost. It was found that copper blunts the acute ventilatory response to hypoxia, ammonia, and combined hypoxia and ammonia exposure. Gill morphometry was also examined and it was found that while copper alone has no effect, when combined with hypoxia exposure it eliminates the increase in filament length and cross-sectional area seen when fish were exposed to hypoxia alone. Furthermore, when neuroepithelial cell size was examined, copper decreased cell projection area with or without the combined presence of hypoxia. Taken as a whole, this thesis indicates that copper exposure can significantly and negatively impact the ability of aquatic organisms to mount appropriate physiological responses to hypoxia.