Dichlorvos alters morphology and behavior in zebrafish (Danio rerio) larvae

Dichlorvos (2,2-dichlorovinyl-dimethylphosphate), an organophosphorus pesticide used for indoor insect and livestock parasite control, is among the most common commercially available pesticides. However, there are significant concerns over its toxicity, especially due to its relative stability in water, soil, and air. Zebrafish, an important developmental model, has been used for studying the effects of toxic compounds. The aim of this study was to evaluate the exposure to dichlorvos at early life stages (1 h postfertilization - 7 days postfertilization) in the zebrafish and its toxicological effects during the development, through morphological (7 days postfertilization), locomotor and social behavior analysis (7, 14, 30, 70, and 120 days postfertilization). Dichlorvos (1, 5, and 10 mg/L) exposure reduced the body length and heartbeat rate at 7 days postfertilization (dpf), as well as the surface area of the eyes (5 and 10 mg/L). The avoidance behavior test showed a significant decrease in escape responses at 7 (1, 5, and 10 mg/L) and 14 (5 and 10 mg/L) dpf zebrafish. The evaluation of larval exploratory behavior showed a reduction in distance traveled, mean speed (1, 5, and 10 mg/L) and time mobile (10 mg/L) between control and dichlorvos groups. In addition, the analysis performed on adult animals showed that the changes in distance traveled and mean speed remained reduced in 30 (1, 5, and 10 mg/L) and 70 dpf (5 and 10 mg/L), recovering values similar to the control at 120 dpf. The social behavior of zebrafish was not altered by exposure to dichlorvos in the early stages of development. Thus, the exposure to organophosphorus compounds at early stages of development induces an increased susceptibility to behavioral and neuronal changes that could be associated with several neurodegenerative diseases.