Anestesia com eugenol em Hypancistrus seideli (Siluriformes: Loricariidae): teste com exposição e reexposição

Abstract

The present study seeks to determine the safe concentration of the anesthetic eugenol for the anesthesia of Hypancistrus seideli, an Amazonian fish endemic to the Xingu River and of importance to the ornamental trade, through an alternative protocol that uses fewer animals than traditional LC50 and LD50 tests. The anesthetic effects of eugenol were analyzed in 64 specimens of H. seideli. For this evaluation, we used the stages already standardized by Ross and Ross in 2008 adapted for loricariids. The fish were randomly chosen and placed individually in aquariums with controlled parameters. Sixty-four specimens of H. seideli were tested, divided into four groups, where groups one and two received 2 mg.L⁻¹ of the anesthetic solution at different times. Group one every minute and group two every two minutes. These same fish were re-exposed to eugenol three months later to determine if there was reverse tolerance in the animals. Groups three and four consisted of fish that had never had contact with eugenol. They received concentrations referring to the averages of the concentrations found in groups one and two, respectively 32.6 mg.L⁻¹ and 24.87 mg.L⁻¹, but without the need for re-exposure after three months. In the preparation of the solution, the eugenol was diluted in 70% ethanol, in a 1:9 ratio. The fish were randomly chosen and observed simultaneously by two researchers. Each fish was tested individually in aquariums containing 5 L of water. The PERMANOVA test was performed, showing that there was no difference in the exposure and re-exposure doses and that the safe anesthesia exposure concentration for H. seideli was 32.6 mg.L⁻¹, where 100% of the fish reached anesthesia in a timely manner. There was no mortality during the experiment, nor months after the tests were performed. The protocol used in this study was effective and safe for the use of eugenol in specimens of H. seideli.