Comparative effects of Chlorpyrifos and Diazinon 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, a widely utilized developmental model, was used to understand the impact of two structurally distinct organophosphates, chlorpyrifos and diazinon, have on vertebrate developmental physiology. Zebrafish embryos were exposed at the pre-epiboly stage to concentrations of pesticides ranging from 1 µM to 1mM and survival, spontaneous movement, 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. However, disruption of physiological processes controlled by the cholinergic neurons was only seen in embryos exposed to chlorpyrifos. Chlorpyrifos exposed embryos exhibited increased spontaneous movements, decreased embryonic heart rate, and decreased larval swimming ability at 5 and 6 days post-fertilization. Although diazinon was more toxic than chlorpyrifos, it had no effect on these physiological systems. These data demonstrate that early developmental exposure to organophosphate pesticides has detrimental effects on vertebrate development and that the mechanism of action may be more complicated than the simple inhibition of acetylcholine esterase.