Anaesthetic and genotoxic effect of medicinal plant extracts in gilthead seabream (Sparus aurata L.)

Anaesthetic properties and potential genotoxicity of six essential oils extracted from the medicinal plants Origanum vulgare, Eugenia aromatica, Aloysia triphylla, Melaleuca alternifolia, Juniperus communis, Cinnamomum zeylanicum, are presently assessed in gilthead seabream. Essential oils are an alternative option for fish anaesthesia, which is necessary in order to ensure welfare under intensively reared conditions. Their anaesthetic efficacy was assessed in comparison with chemical agents, by monitoring fish behavior throughout the anaesthesia and recovery stages, while the post-treatment mortality rate was also recorded. Genotoxicity was evaluated using the single cell gel comet assay in vitro and in vivo. DNA migration (tail moment) and the percentage of cells with increased level of DNA damage in hepatocytes were assessed. All essential oils proved to qualify as anaesthetic agents achieving deep narcosis and behavioural recovery. Essential oils indicated higher efficiency compared to chemicals, mitigating the side-effects that are often associated with synthetic substances. E. aromatic, O. vulgare and A. triphylla induced genotoxic effects at applied doses. However, as genotoxicity is dose dependent and most essential oils usually devoid of long-term genotoxic risk, lower anaesthetic doses have to be tested in order to be proposed for commercial use in aquaculture species. M. alternifolia and J. communis did not induced genotoxicity, maintaining DNA damage at control group level. Finally, C. zeylanicum was evaluated as equal competent anaesthetic agent satisfying the criteria of the ideal anaesthetic, reducing DNA strand breakage and indicating anti-stress, anti-genotoxic and geno-protective effect.Genotoxicity of anaesthetic agents used for fish anaesthesia is an important issue in aquaculture production. As aquaculture fish are intended for human consumption, essential oils are an alternative option for anaesthesia, providing low cost, easy accessibility, efficacy and environmental safety. Due to the fact that essential oils may display dose-dependent toxicity, research on their genotoxic effect is very important before they are suggested for commercial use in aquaculture. The essential oils extracted from medicinal plants Origanum vulgare, Eugenia aromatica, Aloysia triphylla, Melaleuca alternifolia, Juniperus communis, Cinnamomum zeylanicum have never been assessed for their anaesthetic and genotoxic effect in seabream. Furthermore, comet assay is considered as an innovative and validated molecular assay for reliable detection of genotoxicants.