Efeitos do óleo essencial de Elionurus muticus (Spreng.) Kuntze na indução anestésica e no manejo de tilápia do Nilo em diferentes pH da água

Abstract

This study evaluated essential oil from Elionurus muticus (EOEM) as an anesthetic in juvenile Nile tilapia (Oreochromis niloticus) under different water pH conditions. Two experiments were conducted. In Experiment 1, fish (25 g) were exposed to EOEM concentrations ranging from 10 to 600 µL L⁻¹ at pHs 5.5, 7.0, and 8.5 to determine induction and recovery times. In Experiment 2, fish (70 g) were transferred from water at pH 7.0 to waters at pHs 5.5, 7.0, or 8.5, anesthetized (600 µL L⁻¹) or not, and sampled after 0 and 1 h for hematological and plasma biochemical analyses. The 600 µL L⁻¹ concentration was effective for anesthesia, with the shortest induction and recovery times at pH 7.0. Acidic and alkaline conditions prolonged recovery, indicating higher physiological stress. In Experiment 2, after 1 h, non-anesthetized fish at pH 5.5 exhibited elevated hemoglobin levels, while anesthetized fish at pH 8.5 had a reduced hematocrit. Leukocyte and heterophil counts were highest at pH 7.0, especially in anesthetized fish. Anesthesia at pH 7.0 reduced plasma total protein and albumin levels. Hyperglycemia was observed in unanesthetized fish at pH levels of 5.5 and 8.5. Plasma total cholesterol, high-density lipoprotein, and low density lipoprotein levels were higher in the interaction between anesthesia and pH 8.5. These results demonstrate that water pH has a strong influence on the anesthetic efficacy and physiological responses of Nile tilapia exposed to EOEM (600 µL L⁻¹). Optimal performance occurred at pH 7.0, while acidic and alkaline (mainly) conditions increased recovery time and hematobiochemical stress.