Neonicotinoid Imidacloprid Affects the Social Behavior of Adult Zebrafish by Damaging Telencephalon Neurons through Oxidation Stress, Inflammation, and Apoptosis.

The neonicotinoid imidacloprid is a widely used insecticide worldwide. We assessed the effects of acute and chronic imidacloprid exposure on the social behavior of adult zebrafish. We assembled simple apparatus to detect 2D locomotion: a single camera capture system and two specially designed water tanks. We then used the tracking and heat maps of the behavior trajectories of zebrafish subjected to sham and imidacloprid exposure and compared their social behavior. Furthermore, histomorphology and immunohistochemistry of their brain tissue sections were performed to clarify possible neurotoxicity due to imidacloprid exposure in our adult zebrafish. Our results showed that imidacloprid exposure significantly reduced the zebrafish's swimming speed, distance traveled, acceleration, and deceleration. The longer the imidacloprid exposure, the more severe the locomotor behavior disability. Furthermore, imidacloprid exposure significantly reduced heterosexual attractive behavior between the different sexes, as well as defensive alert behavior among males. Our histomorphology and immunohistochemistry evidence showed imidacloprid exposure may lead to neuronal oxidative stress, inflammation, apoptosis, and damage in the telencephalon of adult zebrafish. Thus, we suggested that neonicotinoid imidacloprid exposure can damage the telencephalon neurons of adult zebrafish through oxidative stress, inflammation, and apoptosis and then affect the social behavior of adult zebrafish.