Menthol as anesthetic for juvenile Lophiosilurus alexandri: Induction and recovery time, ventilatory frequency, hematology and blood biochemistry
2022
Ananias, Imaculada de Morais Carvalho | de Melo, Caroline Lopes | Costa, Deliane Cristina | Ferreira, Andre Lima | Ferreira Martins, Edenilce de Fátima | Takata, Rodrigo | Luz, Ronald Kennedy
Anesthesia is an indispensable procedure during the handling of fish. This work evaluated the effects of menthol as anesthetic for juvenile Lophiosilurus alexandri. Menthol concentrations of 0 (control), 25, 50, 150, 300 and 450 mg L⁻¹ were tested using 14 animals for each concentration, with each fish being a replicate. Blood was sampled from seven of the juveniles in each group shortly after anesthetic induction and from the other seven at 24 h post-anesthesia and procedures to collect biometric measures, i.e., handling and air exposure. Induction time showed a linear response plateau effect (LRP) with an inflection point of 142 mg L⁻¹, while a dose-response relationship was observed among concentrations for recovery time. Ventilatory frequency (VF) during anesthetic induction had a LRP effect with an inflection point of 127 mg L⁻¹, while during recovery it had a quadratic effect with a maximum point of 305.45 mg L⁻¹. Fish anesthetized with 50 mg L⁻¹ of menthol had the lowest hematocrit values (P < 0.05), while those exposed to 450 mg L⁻¹ had the lowest erythrocyte values (P < 0.001). Other changes in hemato-biochemical parameters are discussed. Concentrations between 50 and 300 mg L⁻¹ of menthol were able to induce deep anesthesia in juvenile L. alexandri with induction and recovery times considered ideal for fish. The use of 50 mg L⁻¹ of menthol was able to reduce VF during induction and recovery and also prevent increased plasma glucose, with little influence on hematological and biochemical parameters after handling.
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