Essential oils of Ocimum gratissimum and Zingiber officinale as anesthetics for the South American catfish Pseudoplatystoma reticulatum

Abstract

This study evaluated the essential oils of clove-basil (Ocimum gratissimum) and ginger (Zingiber officinale) as anesthetics for the South American catfish Pseudoplatystoma reticulatum and their effects on fish hematology and plasma glucose. For each essential oil, three concentrations were tested (100 mg L−1, 150 mg L−1 and 200 mg L−1) and a control lacking the essential oils was also present. Fish with a mean weight of 40.0 ± 9.9 g were used to provide for 6 replicates per treatment, each fish being a replicate. The times for induction and recovery, as well as the following hematological variables were assessed: Hemoglobin, hematocrit, total number of red blood cells (RBC), total number of white blood cells (WBC), total count of thrombocytes, mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH) in addition to plasma glucose. Significant negative relationships (p < .05) were observed between essential oil concentration and induction time, with the O. gratissimum essential oil resulting in lower times. A significant positive relationship (p < .05) between recovery time and essential oil concentration was observed only for the O. gratissimum essential oil. Anesthesia with the O. gratissimum essential oil did not affect the fish hematology and plasma glucose. In contrast, significant relationships were found between the Z. officinale essential oil concentration and hemoglobin, hematocrit and MCHC (p < .05), possibly indicating hemoconcentration. This study demonstrated that both O. gratissimum and Z. officinale essential oils are capable of inducing anesthesia in P. reticulatum, although the former presented better results, considering the lower induction time and the fact that fish hematology was not affected.