Effects of Natural and Synthetic Pesticides on D. rerio Locomotion

Abstract

Pesticide pollution is a serious problem in the world, particularly in places with a close proximity to the ocean. When these chemicals inevitably leak into groundwater or runoff, humans and animals alike can be exposed to them and subsequently put at an increased risk of neurotoxic responses, birth defects, and cancer. This study sought to determine whether or not natural alternatives to pesticides–in particular, neem oil–might have lesser effects on aquatic life and human nervous systems than synthetic pesticides. In order to do so, larval D. rerio (≤7dpf), a species commonly used as a model organism for nervous system function, were separated into three different treatment groups: one was treated with a 20 μg/L concentration of Sawyer Insect Repellent (active ingredient permethrin), one was treated with the same concentration of neem oil (natural pesticide), and one was left untreated to act as a control group. Short videos of these groups were recorded daily for three consecutive days, after which time the movement patterns in the videos were tracked and analyzed. It was determined that exposure to synthetic pesticides caused a significant (p value <0.01) increase in the distance traveled by the D. rerio, suggesting a neurotoxic response. The fish that were placed in the neem oil solution were notably harmed as well, exhibiting body axis curvature accompanied by an inability to swim straight forward; by the second day, all fish in the neem oil group had died. These findings suggest that neem oil as a natural pesticide might actually be just as detrimental to human and D. rerio nervous systems as compared to synthetic pesticides, if not even worse. This study could provide a basis for further investigation into alternatives to conventional pesticides, and demonstrates the alarming fact that “natural” doesn’t necessarily mean “safe”.