ESSENTIAL OIL FROM Peumus boldus: A NEW ANESTHETIC FOR TILAPIA FINGERLINGS

In the last decade, several studies investigating alternatives to replace the synthetic anesthetics , A novel alternative  could be the essential oils (EO). To date, EO of different plants have been studied for fish anaesthesia; most of them belong to Lamiaceae , Verbenaceae , Lauraceae and Myrtaceae (Hoseini et al., 2018) . However, there are no studies using Peumus boldus as anesthetics in tilapia fingerlings. Therefore, the aim of this study was to evaluate the effectiveness of EO as an anaesthetic.

To obtain EO form  P. boldus , it was used dry leaves of the plant by water-steam distillation for 2 h using Clevenger type apparatus. A gas chromatography-mass spectrometry (GC-MS) analysis was performed at Instituto de Pesquisas de Produtos Naturais da Universidade Federal do Rio de Janeiro, to determinate the percentage of the EO compounds. To determine the acute toxicity test, lethal doses (LD50) at 48 h was calculated, t he concentration of the EO ranged from 50 , 100, 200, 300 up  to 800 µL L-1. For anaesthesia induction and recovery, tilapia fingerlings (2.66 ± 0.16) were transferred to aquaria that contained 500 mL of water and different concentration of P. boldus EO (100, 200, 300, 400, 500, 600, 700, and 800 µL L-1) . A 15-tilapia fingerlings were used for each concentration tested, and each fingerling was used once. The stages of anaesthesia in fish was according to Zahl , Samuelsen & Kiessiling (2012).

The major components of the EO of  P. boldus was 3-Cyclohexene-1-methanol, alpha.,. alpha.,4-trimethyl-, acetate (30.33%), Eucalyptol (19.35% ), o-Cymene (15.57% ), and 2-Piperidinone, N-[4-bromo-n-butyl] (15.40%) .

The LD50 at 48 h was 109 µL L-1 .  An efficacious anaesthetic should induce anaesthesia within 15 min and preferably <3 min with a recovery of 5 min or less (Marking & Meyer 1985).  The essential oils of  P. boldus i nduce the deep narcosis stage (Plane 3) in less than 3 min, at 300 to 800 µL L-1 . T he recovery time ranged from 304-500 seg . T he essential oil induced anaesthesia without mortality in tilapia fingerlings .