Exposure to Fipronil Induces Behavioural Effects on Early-Life Stages of Danio rerio
摘要
Fipronil (FIP), an insecticide widely used in crop protection, animal health, and indoor pest control, may present a significant risk factor for the environment, wildlife, and human health due to its high lipophilicity. The current research looked at the sublethal effects of FIP on Danio rerio embryos, using a novel approach that integrates two different behavioural responses of organisms: the measurement of locomotory activity after “forced” exposure to the compound and the avoidance behaviour using a “non-forced” exposure multi-compartment system. In the first approach, freshly fertilized eggs were exposed for 120 h to FIP (0, 0.03, 0.06, 0.12, 0.24, and 0.48 mg L−1) evaluating, in addition to locomotor activity, the survival, developmental parameters, and acetylcholinesterase (AChE) activity as a marker of neurotoxicity. In the non-forced exposure approach, the avoidance behaviour of 6 days-old larvae of D. rerio to a linear gradient of FIP (0, 0.05, 0.07, 0.11, 0.17, and 0.24 mg L−1 FIP) was assessed for a period of 4 h. In the forced exposure, FIP decreased the swimming activity (for instance the distance travelled by larvae increased 66% at 0.48 mg L−1 compared to control) and changed swimming pattern (locomotion angles denoting erratic swimming increased from 10% in the control to 30% at 0.48 mg L−1). Furthermore, AChE activity in FIP-exposed fish was significantly inhibited after 120 h of exposure (AChE activity was 30% inhibited in fish exposed to the highest concentration tested when compared to control). The 4-h avoidance assay indicated that organisms could not escape from the higher FIP concentration compartments. This lack of avoidance capacity suggests rapid action of FIP, impairing the locomotory capacity of larvae to move away from toxic stress. This is partly corroborated by the significant AChE depressed activity, indicative of the disruption of cholinergic pathways by FIP and consequent disruption of locomotion function, as also seen by the depressed swimming activity. In this work, the integrated analysis of the two behavioural tests highlights the potential of behavioural parameters for an accurate assessment of pesticide risks to aquatic environments, as these parameters are easily linked with ecological functions (mating, feeding, avoidance, and response to predators) with implications at the population level and that cannot be easily evaluated through conventional endpoints used in ecotoxicology (e.g., mortality).