Document Type

Honors Thesis

Publication Date

Spring 2019

Abstract

The goal of this study is to determine the effect of arsenic exposure on vision in zebrafish (Danio rerio). The optic system of D. rerio is ideal for examining visual defects. Their eyes are similar to eyes of humans and can therefore be useful models in studies of human eye disease. Their optic system functions similarly to humans, so it is beneficial to observe how zebrafish are affected by contaminants in the environment. Arsenic is ubiquitous in groundwater, due to its natural presence in bed rock, but is elevated by human activities. In order to see any immediate effects on vision by arsenic, a behavioral assay was used. Due to accumulation in eye tissues, we predict that visual acuity will decrease with increased exposure to arsenic. Zebrafish embryos were exposed to 0, 10, 50, and 500 parts per billion of arsenic. At five days post hatch, a striped, rotating cylindrical drum created a pattern designed to elicit the optomotor response in zebrafish. Time spent following and going against the striped pattern was calculated to determine if the optomotor response was evoked in the zebrafish. A positive value would indicate an optomotor response, and a negative value would indicate no response. The control group did not behave as expected, as they showed a negative value in response to the cylindrical drum. Statistical analyses revealed a batch effect in this data set, and the total distance travelled showed a significant difference in activity level between batch one and batches two and three. Batch one showed an unexpected positive trend in optomotor response with increased arsenic exposure, with 50 ppb arsenic treatment group following the rotational pattern of the striped drum for a longer amount of time relative to the control. Batches two and three showed no significant differences between arsenic treatments and the control group. Changes in experimental design may result in the expected control behavior, and further replication would be necessary to determine any effects of arsenic on vision in zebrafish.

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