Pesticide-Induced Alterations in Zebrafish Behavior, Histology, and Gene Expression: An Integrated Approach

MARIANA BIANCHI; ENRIQUE PARAVANI; MARIA GABRIELA ACOSTA; LUCIA M. ODETTI; MA. FERNANDA SIMONIELLO; GISELA L. POLETTA

Montevideo

Congreso; SETAC Latin America 15 th Biennial Meeting; 2023

SETAC

Pesticides, after being applied, are distributed in the environment and can be retained, degraded and/or transformed, or transported outside the application site. Chronic exposure of organisms to low concentrations of these compounds can have cumulative sublethal effects, influencing metabolism, fitness, and reproductive success, hence producing effects at the population level. The impact of pesticides on natural populations is often underestimated or unknown. To evaluate the effect of the herbicides glyphosate and 2,4-D and the insecticide imidacloprid, individually and through the mixture of them, under environmentally relevant concentrations, adult zebrafish (Danio rerio) were used. Bioassays were performed exposing the animals for 96 hours with daily changes of the solutions. Analysis of the behaviour, as well as histology of the gills and expression of genes involved in the pathways of oxidative stress and cell apoptosis were performed. In behavioral studies, it was found a significant lower mean swimming speed (Vmed) in animals exposed to the mixture of products, compared to the controls . The histological study showed significant differences in the tissue structures. Exposure to imidacloprid [20%] produced mild (G1) lesions, whereas to glyphosate [0.5 mg/L] it produced moderate (G2) to severe (G3) lesions. Regarding the analysis with the herbicide 2,4-D [0.8 mg/L] and the mixture of all the compounds, severe lesions were observed (G3). Gene expression studies showed an overexpression of the genes involved in the oxidative stress and the cell apoptosis pathways, while in all cases there was evidence of a decrease in the expression of the ogg1 gene (involved in the DNA repair). These results indicate that the pesticides cause strong behavioral, morphological, and molecular changes, being able to trigger cell apoptosis, in the gills of zebrafish exposed to environmental concentrations. There is a clear need to continue this type of research on the ecological consequences of these compounds in the environment.