A Senior Capstone Experience by Evan Merk ’25

Submitted to the Departments of Environmental Science and Studies

and of Biology

Advised by Dr. Martin Connaughton and Dr. Leslie Sherman

Contributor Biography: Evan Merk (he/him) is a recently-graduated biology and environmental science major. On campus, he was a biology lab teaching assistant, Writing Center peer tutor, and an active participant in drama department productions.

Description: This study sought to learn the effect of copper sulfate (CuSO₄) exposure on the visual development of larval Danio rerio, also known as zebrafish. Zebrafish were acquired at 1 day post fertilization (dpf) and exposed to either 0, 0.25, 0.75, or 1.25 mg/L CuSO₄ solution for 72 hours, and then moved out of solution to continue developing until 9 dpf. On 9 dpf, zebrafish were photographed under a microscope for later length measurement using ImageJ. Zebrafish were also run through an optokinetic response (OKR) behavior assay to determine if the fish are visually processing information. The OKR was run for 30 seconds clockwise and 30 seconds counterclockwise, and the summed number of saccades, or eye movements, was determined. The difference in mean summed saccades between the 0 mg/L, 0.75 mg/L, and 1.25 mg/L treatments was significant, with a decrease in the number of saccades matching the increase in CuSO₄ concentration. The difference in average length between treatments was not significant, with no strong visual trend in the results. These results imply that visual development in larval Danio rerio is negatively impacted by CuSO₄ concentrations. As the vertebrate eye is highly conserved, the zebrafish can serve as a model for human visual development, and negative impacts of CuSO₄ exposure on human visual development might be of concern. 

Read Evan’s SCE below: