There is an increasing demand for inexpensive and safe anesthetics that can reduce fish stress caused by some procedures such as capture and handling. In this context, the present study evaluated the potential of essential oils (EO) of three Brazilian native plants (Hesperozygis ringens, Lippia sidoides and Ocotea acutifolia) as anesthetics for the silver catfish - Rhamdia quelen. Moreover, an analysis was made of the chemical composition of these oils and their influence on stress parameter. EO of H. ringens and O. acutifolia were effective as anesthetics, without behavioral side effects. EO of O. acutifolia (150 µL L-1) promoted an increase in blood glucose level. Regarding to the composition, pulegone accounts for 96.63% of the EO of H. ringens, and caryophyllene oxide amounts to 56.90% of the EO of O. acutifolia. Two chemotypes, thymol and carvacrol (68.40% and 67.89%, respectively) were verified for EO of L. sidoides. Both samples of EO of L. sidoides showed anesthetic activity in silver catfish, but exposure also caused loss of mucus and mortality. Thus, only the EO of H. ringens and O. acutifolia are advised for anesthetic use

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The anesthetic activities of the essential oils (EOs) of Hesperozygis ringens (EOHR) and Lippia alba (EOLA) and their effects in silver catfish (Rhamdia quelen) after anesthesia and recovery were investigated. Fish (32.19 ± 1.24 g) were submitted to one of the following treatments for each EO: basal group, control, or anesthesia (150, 300, or 450 μL L(-1) EO). After that the anesthesia was induced or simulated and the biometric measurements were completed, fish were transferred to anesthetic-free aquaria to allow for recovery. Fish were sampled at 0, 15, 30, 60, and 240 min after recovery. At time 0 of recovery, the ventilatory rate was lower in the groups anesthetized with either EO. In comparison with the basal group, control fish showed an increase in plasma glucose, aspartate aminotransferase (AST), and Na(+) levels and a reduction in Na(+)/K(+)-ATPase activity at 0 min of recovery. Plasma levels of ammonia and Na(+) were lower in the fish anesthetized with EOLA (450 μL L(-1)) and EOHR (all concentrations), respectively, than in the control fish. Additionally, lactate, AST, alanine aminotransferase, K(+) plasma levels, and gill Na(+)/K(+)-ATPase and H(+)-ATPase activities were higher in the fish anesthetized with either EOHR or EOLA than in the control fish. The EOs promoted slight changes in silver catfish that enabled both an adaptive response and the recovery of most of the measured parameters after 240 min regardless of concentration or EO that was used. These findings support the use of EOHR and EOLA as anesthetics for fish.

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The aim of this study was to evaluate the anesthetic activity of the essential oil (EO) of Ocimum americanum L. in silver catfish (Rhamdia quelen). In the first experiment, the depressor effects and chemical composition of the leaf EO (LEO) and inflorescence EO (IEO) were compared. Juveniles (n = 10) were placed in aquaria containing different concentrations of EO (25 -500 mg L -1 ) to determine the point at which anesthesia was induced and the length of the recovery period. In the following experiment, the effects of 300 and 500 mg L -1 LEO exposure on stress parameters (plasma cortisol, glucose and sodium levels) after air exposure for 1 min were assayed. Fish (n = 10 per sampling time) were sampled immediately or transferred to anesthetic-free aquaria until sampling (15, 30, 60 or 240 min). LEO was composed mainly of β-linalool and 1,8-cineole in similar proportions, whereas IEO showed β-linalool as major compound. Anesthesia was obtained in silver catfish with 200-500 mg L -1 between 4-8 min for LEO and 6-16 min for IEO. Lower EO concentrations did not reach anesthetic stage up to 30 min. LEO used as anesthetic prevented the cortisol increase and sodium loss induced by aerial exposure. Glucose levels were raised in catfish exposed to LEO compared to basal group (not air exposed) in almost all observation times. EO of O. americanum obtained from leaves was considered suitable to anesthetic procedures due to its fast induction and handling-induced stress prevention.O objetivo deste trabalho foi avaliar a atividade anestésica do óleo essencial (EO) de Ocimum americanum L. em jundiás (Rhamdia quelen). No primeiro experimento, os efeitos depressores e a composição química dos óleos obtidos a partir das folhas (LEO) e das inflorescências (IEO) desta espécie vegetal foram comparados. Para isto, juvenis de jundiás (n = 10) foram transferidos para aquários contendo diferentes concentrações de EO (25 -500 mg L -1 ) a fim de determinar os tempos de indução aos estágios de anestesia e de recuperação. No experimento seguinte foram determinados os efeitos da exposição a 300 e 500 mg L -1 de LEO em parâmetros de estresse (cortisol, glicose e níveis de sódio plasmáticos) após os animais serem expostos durante 1 min ao ar. Os peixes (n = 10 por tempo de amostragem) foram coletados imediatamente ou transferidos para aquários livres de anestésico até amostragem (15, 30, 60 ou 240 min). LEO demonstrou ser composto majoritariamente por β-linalol e 1,8-cineol em proporções similares, enquanto que IEO apresentou β-linalol como constituinte majoritário. O estágio de anestesia foi verificado em jundiás com 200-500 mg L -1 entre 4-8 min para LEO e 6-16 min para IEO. Menores concentrações de ambos os EO não promoveram anesthesia até 30 min. O uso de LEO como anestésico preveniu o aumento de cortisol e a perda de sódio induzida pela exposição aérea. Já a glicemia encontrava-se aumentada em peixes expostos ao LEO em comparação ao grupo basal (não exposto ao ar) na maioria dos tempos de observação. Assim, EO de O. americanum obtido a par...

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