Aquaculture xxx (xxxx) xxx Please cite this article as: Arlene Sobrinho Ventura, Aquaculture, https://doi.org/10.1016/j.aquaculture.2020.736124 Available online 3 November 2020 0044-8486/© 2020 Elsevier B.V. All rights reserved. Ocimum basilicum essential oil as an anesthetic for tambaqui Colossoma macropomum: Hematological, biochemical, non-specifc immune parameters and energy metabolism Arlene Sobrinho Ventura a, * , Gabriela Tomas Jerˆ onimo b , Ruy Alberto Caetano Corrˆ ea Filho a , Alda Izabel de Souza a , Giovanna Rodrigues Stringhetta a , Matheus Gomes da Cruz c , Gabriel dos Santos Torres b , Ligia Uribe Gonçalves d , Jayme Aparecido Povh a a Faculty of Veterinary Medicine and Animal Science (FAMEZ), Federal University of Mato Grosso do Sul, Av. Sen. Filinto Müller, 2443, Campo Grande, MS 79070-900, Brazil b Federal University of Amazonas (UFAM), Av. Rodrigo Ot´ avio, 6200, Manaus, AM 69080-900, Brazil c Nilton Lins University, Av. Prof. Nilton Lins, 3269, Manaus, AM 69058-300, Brazil d National Research Institute of the Amazon (INPA), Av. Andr´ e Araújo, 2936, Manaus, AM 69060-001, Brazil A R T I C L E INFO Keywords: Anesthetic Stress Physiology Metabolism ABSTRACT The present study evaluated the effcacy of Ocimum basilicum (basil) essential oil in the anesthetic induction and recovery of juvenile tambaqui Colossoma macropomum and verifed its physiometabolic effects after biometric handling. Juveniles (86.51 ± 7.82 g) were exposed to different concentrations of basil essential oil: 400, 500, 600, 700, 800, 900, and 1000 μL L 1 . Subsequently, the fsh were divided into fve groups: control (non-handled fsh), handling without anesthetic (water only), handling with ethanol (720 μL L 1 ), and handling with Ocimum basilicum essential oil (400 and 800 μL L 1 ). The shortest (p < 0.05) time to induce anesthesia was at a con- centration of 1000 μL L 1 (222 s). The recovery time from anesthesia did not differ signifcantly among different concentrations (400–1000 μL L 1 ). The results of the present study confrm the essential oil of O. basilicum as a new and safe natural anesthetic for juvenile tambaqui. The use of this essential oil in biometrics handling pro- cedures reduces or attenuates the secondary responses to handling stress without showing deleterious effects on the non-specifc immune system or metabolism of energy, carbohydrates, and lipids. However, further studies are necessary to determine the exact mechanism of action of this essential oil. 1. Introduction Tambaqui Colossoma macropomum (Cuvier, 1816), from the Amazon Basin, is one of the most important native fsh in South America. In 2018, its production, at 102,554 tons (IBGE, 2020), was the second highest of all aquatic organisms in Brazil. Tambaqui aquaculture’s success is due to its rusticity, high commercial value, high level of acceptance by consumers, fast growth, omnivorous feeding behavior, and adaptation to farming (Morais and O’Sullivan, 2017). Although tambaqui is highly tolerant of farming conditions, it can be adversely affected by excessive handling (Morais and O’Sullivan, 2017). There- fore, the use of anesthetics during routine aquaculture practices is necessary to mitigate the stress effects that directly affect fsh physiology and welfare (Ross and Ross, 2008; Velisek et al., 2011). Several studies have evaluated the sedative and anesthetic potential of essential oils from various medicinal plants for tambaqui handling (Boijink et al., 2016; Barbas et al., 2017a, 2017b; Saccol et al., 2017; Baldisserotto et al., 2018; Batista et al., 2018; Hoseini et al., 2019; da Silva et al., 2019; da Souza et al., 2019; Vilhena et al., 2019). In addition, other products of plant origin, such as an extract of Spilanthes acmella (Barbas et al., 2016) and Lippia alba hydrate (Maia et al., 2019), have also been evaluated. These products are presented as alternatives to synthetic drugs, such as MS-222, which are expensive and are often unavailable in Latin American countries (Popovic et al., 2012). Biometric handling and transportation are routine practices in farms producing tambaqui and are likely to trigger secondary responses to * Corresponding author at: Faculty of Veterinary Medicine and Animal Science (FAMEZ), Federal University of Mato Grosso do Sul (UFMS), Av. Sen. Filinto Müller, 2443, Campo Grande, MS 79070-900, Brazil. E-mail address: arlenesventura@gmail.com (A.S. Ventura). Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture https://doi.org/10.1016/j.aquaculture.2020.736124 Received 11 August 2020; Received in revised form 3 October 2020; Accepted 30 October 2020