Genotoxicity evaluation of three anesthetics commonly employed in aquaculture using Oreochromis niloticus and Astyanax lacustris

The use of non-plant and plant-derived anesthetics in aquaculture activities is a frequent and necessary practice to maintain fish welfare. Currently anesthetics authorized for use in aquaculture activities are limited, and the use of unauthorized products is common. However, to obtain authorization for use in aquaculture and ensure their safety, anesthetics should be evaluated for their genotoxic potential. Our objective was to evaluate the genotoxicity of three not approved anesthetics commonly used in aquaculture using Astyanax lacustris and Oreochromis niloticus. Both fish species were exposed to six treatments: two with commercial anesthetics (benzocaine and eugenol), one with Lippia alba essential oil (EO), and three controls - negative (without treatment), vehicle (ethanol PA), and positive (cyclophosphamide). Fishes were exposed to all treatments in a water bath for 10 min and were transferred to individual aquariums without anesthetics or controls. Venipuncture of the caudal vein was performed 72 h after the exposure to the anesthetics. Nuclear abnormalities and the micronucleus were analyzed in blood smears, and DNA damage was assessed using comet assay. No genotoxicity effects were verified for fishes exposed to L. alba EO. Eugenol presented genotoxicity to both species. The comet assay showed increased DNA damage in both species induced by benzocaine and eugenol. Thus, L. alba EO was proven to be the safest anesthetic resulting in no genotoxicity and, therefore, may be an interesting alternative to commercial anesthetics used in aquaculture. However, a complete toxicological evaluation is necessary to ensure the safety of its use as an anesthetic.