Evaluation of the toxicity of the pesticide acephate and its by-product methamidophos over the behaviour of zebrafish Danio rerio (Cypriniformes, Cyprinidae)

Depending on its concentration and bioavailability, the pesticide acephate and its by-product methamidophos may cause deleterious effects on the physiology and behaviour of various animals when in contact with water. Studies investigating the negative impacts of acephate in animals have used zebrafish larvae as a model species, but the effect on adult individuals remains unclear. Our main objective was to assess the behavioural changes in adult zebrafish (Danio rerio) exposed to acephate and methamidophos. To this end, 160 individuals of zebrafish were divided into three groups: acephate, methamidophos (exposed) and control groups (non-exposed), where subjects in the treatment groups were exposed to 7 µg/L of acephate and 7 µg/L methamidophos for 28 days. To compare the groups, behavioural assessments were conducted using scan sampling with instantaneous behaviour recordings every 30 s for ten minutes each day. Fish behaviour and fish location in the water column were compared between treatment and controls using Generalized Linear Mixed Models. The results showed an alteration in swimming patterns, an increase in aggression, an increase in abnormal behaviours and other stress-related behaviours, such as gasping for air, provoked by acephate and methamidophos. These behavioural alterations may have serious consequences for wild fish communities, such as an increased risk of predation and may contribute to the extinction of local populations. These findings highlight the usefulness of behaviour in assessing the environmental impact caused by pesticides.