The effect of copper nanoparticles on olfaction in rainbow trout (Oncorhynchus mykiss)

Abstract

Although olfactory toxicity of copper (particularly Cu²⁺) in fish has drawn considerable research attention, the impact of copper nanoparticles (CuNPs) on the olfactory system is not well characterized. The main objective of this study was to investigate the time-dependent effects of CuNPs and Cu²⁺ on olfactory sensitivity and olfactory-mediated behaviours of rainbow trout (Oncorhynchus mykiss). To establish olfactory-impairment thresholds, 24 h inhibitory concentration (IC) curves, induced by CuNPs or Cu²⁺ on ciliated and microvillous olfactory sensory neurons (OSNs) were determined using electro-olfactography (EOG). The results indicated ciliated cells are more sensitive to both CuNPs and Cu²⁺ exposure relative to microvillous OSNs. Thus, the concentration of contaminants that induced 50% inhibition in ciliated OSNs (24 h-IC50; 322 and 7 μg L⁻¹ for CuNPs and Cu²⁺, respectively) were selected as equi-toxic concentrations. Fish were exposed to 24 h-IC50 concentrations for 24 h or 96 h, and their olfactory sensitivity was studied using EOG and a behavioural assay. Results of EOG demonstrated a gradual, time-dependent increase in the inhibitory effect of CuNPs, whereas fish under Cu²⁺ exposure displayed a partial recovery at 96 h, as compared to the 24 h time point. Fish behavioural results followed a similar pattern as in neurophysiological experiments. Overall, exposure to CuNPs resulted in a different time-dependent toxicity pattern on the fish olfactory system than Cu²⁺ after exposure at equi-toxic concentrations. Our data suggest that CuNPs and Cu²⁺ affected chemosensory function and behaviour differently in rainbow trout.