Single Acute Sublethal Fipronil Concentration Induces Behavioral Toxicity And Suggests Endocrine-Disrupting Properties In Zebrafish

Abstract

Fipronil (FPR), a second-generation phenylpyrazole insecticide, is used in Veterinary Medicine, agriculture, and horticulture against fleas, ticks, ants, cockroaches, and other pests. By selectively inhibiting gamma-aminobutyric acid receptors in vertebrates and invertebrates, studies suggest that acute exposure harms sensory and motor systems, and long-term exposure has an endocrine-disrupting effect. The main objective of this study was to investigate the effects of a sublethal concentration of FPR on the behavior of adult zebrafish, using them as an assessment model to detect early Central Nervous System toxicity. First, to achieve this dose, we exposed the fish to several FRP concentrations and monitored lethality for up to 72 h.  Using the FRP sublethal concentration, the behavioral signs of toxicity were observed in the exploratory behavior in the open field, anxiety-like behavior, and social and sexual preferences. The results showed that the sublethal concentration of FRP was 0.5 µg/L. Under this concentration, the fish exhibited significant behavioral changes in the aquarium, including tremors, increased movement frequency and duration, and a longer time to reach the surface. Furthermore, an increase in anxiolytic-like behavior, and a reduction in social and sexual preferences, without interference in the open field exploration, were observed. Thus, our data indicate that acute exposure to sublethal concentrations of FPR induces neurotoxic effects that can be attributed to its GABAergic antagonist action. The FRP endocrine disruptor could, in part, be due to reduced sexual preference, with ecotoxicological importance for fish reproduction. Thus, the present results validate the use of the zebrafish model as a tool in studies related to FPR neurotoxicity.