Impactos neuroendócrinos e comportamentais de um inseticida à base de imidacloprid em zebrafish

Abstract

Zebrafish is a well-established model organism for translational and ecotoxicological research. Despite having the genome completely sequenced and the behavior and physiology well reported, there are some issues related to the housing and management of these animals that are still poorly understood. Considering the issues regarding the housing of the zebrafish, we aimed to investigate whether different cues, used alone or together, would interfere in zebrafish behavior. In this study, we detected that the animals have different behaviors when in the presence of isolated cues and together, therefore, we emphasize the importance of the description and detailing of the conditions of housing of these fish. After the development of this first article, we had the idea of working with imidacloprid (IMI). IMI is an insecticidal pesticide used globally in the treatment of seeds and leaves of crops such as vegetables, sugar beet, cotton and tobacco. The use of IMI is mainly due to its high insecticidal potential and low toxic potential in mammals, acting as a specific nicotinic acetylcholine agonist for invertebrate receptors. However, non-target species have been affected by this compound, which can cause from the mortality of these animals to endocrine and physiological changes in sublethal concentrations, mostly based on the LC50/LD50 (concentration/dose capable of killing 50% of the population tested), in chronic or acute exposures, within 96 hours. However, little is known about the effect that concentrations already detected in the environment and in periods shorter than 96 hours can have on non-target organisms. Therefore, our aim was to analyze whether an IBI (imidacloprid-based insecticide) alters behavior, cortisol levels and redox status in zebrafish, in a 30-minute exposure protocol and at environmentally relevant concentrations. In this second manuscript, we showed that IBI was able to reduce locomotion, social and aggressiveness behaviors of exposed fish, in addition to inducing a mild anxiolytic-like effect. Furthermore, we observed an increase in trunk cortisol, protein carbonylation and a decrease in nitric oxide levels in the ex vivo analysis. These in vivo and ex vivo changes were mostly identified in animals exposed to 0.0013; 0.013 and 0.13μg.L-1 of IBI. All these imbalances and losses triggered by the IBI so quickly, in an environmental context, can interfere with the fish ability to escape from possible predators, and consequently, the survival of the animal in environment.