Behavioral effects in adult zebrafish after developmental exposure to carbaryl

In recent years, there is a growing concern to correctly assess the risk of low environmental concentrations of contaminants (e.g. pesticides) to aquatic life. Pesticides can be found in the ng/L and µg/L range and, very often, observable effects to non-target organisms like fish, may not be perceptible immediately and long term effects can be underestimated. Hence, our work intends to evaluate the effect of an early (embryonic) exposure to carbaryl in adult fish behaviour. Zebrafish (Danio rerio) embryos were exposed to 4 sublethal concentrations (0, 10, 100 and 1000 mg/L) of carbaryl during 4 days and then kept in standard cultivation conditions until adulthood. Two behaviour tests were then performed to assess anxiety-like behavior (novel tank test and light/dark stimulus) plus a feeding test. Our data showed that zebrafish pre-exposed to car- baryl, remained longer periods in the bottom layer of the aquarium suggesting a decrease of the exploratory behavior. Further, fish pre-exposed to 1000 mg/L of carbaryl showed lower swimming activity (distance moved and time spent swimming) than non-exposed fish and presented reduced thigmotaxis during the dark stimulus when compared to control, suggesting repression of anxiety-like behavior. Pre-exposed fish also took more time to feed than non-exposed fish. Our results show that developmental exposure to carbaryl has long lasting effects on adult behaviour highlighting the importance of the environmental conditions during early life stages of organisms. Moreover, this work shows the importance of assessing the effects of chemicals in relevant exposure scenarios that take into account long-term effects.