Effect of chlorinated organophosphate pesticides on zebrafish developmental physiology
Authors:Hena Garcia, Natalie Hole, Flaka Radoniqi, Hayden Schmidt
Mentor:Erica Fradinger, Assistant Professor of Biology, Whittier College
Organophosphate pesticides are known to inhibit acetylcholine esterase, an enzyme that degrades acetylcholine at the cholinergic synapse. In this study zebrafish (Danio rerio), a widely utilized developmental model, was used to understand the impact of two structurally similar organophosphates, chlorpyrifos and dichlorvos, on vertebrate developmental physiology. Zebrafish embryos were exposed at the pre-epiboly stage to concentrations of pesticides ranging from 1μM to 1mM. Survival, spontaneous movements, heart rate, swimming behavior, and physical abnormalities were examined. Both pesticides were found to be toxic to developing zebrafish embryos at concentrations at or greater than 100 μM and sub-lethal concentrations resulted in disruption of physiological processes controlled by the cholinergic nervous system. Embryos exhibited increased spontaneous movements, decreased embryonic heart rate, and decreased larval swimming activity at 5 and 6 days post-fertilization. At 10 days post-fertilization, no differences in swimming activity were observed between exposed and non-exposed embryos. However, exposed embryos exhibited short bursts of movement whereas the non-exposed embryos exhibited prolonged, smooth swimming movements. Overall, the physiological effects were more pronounced in embryos exposed to chlorpyrifos than in embryos exposed to dichlorvos. Therefore, early developmental exposure to chlorinated organophosphate pesticides has detrimental effects on the cholinergic physiology of the zebrafish embryo.