Histopathological and Behavioral Impairments in Zebrafish (Danio rerio) Chronically Exposed to a Cocktail of Fipronil and Pyriproxyfen

Background: Lately, the high incidence of pesticide usage has attracted everyone’s interest due to the serious effects produced. Fipronil (FIP) is a phenylpyrazole compound that acts on the insect’s GABA neurotransmitter by inhibiting its activity. Moreover, the literature reports highlight its implication in neurodevelopmental abnormalities and oxidative stress production in different organisms. Similarly, pyriproxyfen (PYR) is known to affect insect activity by mimicking the natural hormones involved in the maturation of the young insects. The aim of the present study was to investigate the impact of the mixture of these pesticides on the tissues and behavior of zebrafish. Methods: To assess the influence of this cocktail on zebrafish, three groups of animals were randomly selected and exposed to 0, 0.05, and 0.1 mg L−1 FIP and PYR mixture for five days. The fish were evaluated daily by the T-maze tests for locomotor activity and the light–dark test and recordings lasted four min. The data were quantified using the EthoVision software. Results: Our results indicated significant changes in locomotor activity parameters that showed increased levels following exposure to the mixture of FIP and PYR. On the other hand, the mixture also triggered anxiety in the zebrafish, which spent more time in the light area than in the dark area. In addition, mixture-induced histological changes were observed in the form of numerous hemosiderin deposits found in various zebrafish tissues. Conclusions: The current findings indicate that the mixture of FIP and PYR can have considerable consequences on adult zebrafish and may promote or cause functional neurological changes in addition to histological ones.