Anesthetic induction and recovery of Hippocampus reidi exposed to the essential oil of Lippia alba

The aim of this study was to identify the times of anesthetic induction and recovery in slender seahorses (Hippocampus reidi) that were exposed to the essential oil of Lippia alba (EO), as well as the efficacy of EO as a stress-reducing agent in the transport of this species. Slender seahorses were placed in 1-L aquaria containing different concentrations of EO (0, 10, 20, 50, 150, 300 and 450 mu L L-1), and after induction, fish were transferred to aquaria that were free of anesthetic to evaluate their recovery time. In an additional experiment, slender seahorses were transported in plastic bags with 15 mu L L-1 of EO for 4 or 24 h. The increased concentration of EO proportionally decreased the time required for the induction of anesthesia. EO treatment (15 mu L L-1) inhibited the increase in blood glucose levels that was provoked by transportation for 4 or 24 h. Transportation for 24 h also decreased the number of lymphocytes and increased the neutrophil count, and these effects were avoided with the addition of EO to the water. These results demonstrate that EO was effective as an anesthetic at concentrations of 10-20 mu L L-1 for slight sedation and transport and at 150 mu L L-1 for deep anesthesia in the slender seahorse.