Essential oils of Lippia sidoides and Mentha piperita as reducers of stress during the transport of Colossoma macropomum

This study evaluated the use of the essential oils of Lippia sidoides (EOLS) and Mentha piperita (EOMP) as a stress reducer in the transport of Colossoma macropomum. The fish were transported for four hours in plastic bags, comprising the following treatments: a) non - stressed control (NS - not submitted to transport stress), b) stressed control (S - submitted to transport), c) EOLS 10 mg L−1, d) EOLS 20 mg L−1, e) EOMP 20 mg L−1 and f) EOMP 40 mg L−1; each treatment with three repetitions. After transportation, water quality, hormonal, biochemical and enzymatic parameters were analyzed. C. macropomum transported with EOLS 20 mg L−1 showed a significant reduction in cortisol levels compared to fish transported without essential oil. The glycolytic pathway was particularly stimulated in fish transported with EOMP 20 mg L−1, since the values of glycolytic enzymes hexokinase (HK), pyruvate kinase (PK) and lactate dehydrogenase (LDH) were elevated in muscle tissue. The essential oils did not affect the activity of acetylcholinesterase (AChE) in the brain of C. macropomum and, after transport, the fish from all treatments showed a significant reduction (28.2%) of muscular AChE. The concentrations of EOLS 20 mg L−1 and EOMP 20 mg L−1 promoted increased levels of the enzyme glutathione S-transferase (GST) in the brain. It is concluded that the essential oils in the assessed concentrations tend to improve water quality during transport, minimize physiological stress, help maintain energy demand through the breakdown of hepatic glycogen, glucose production and activation of the glycolytic pathway, however, without accumulating lactate. Furthermore, AChE trials demonstrate that EOs may not have neurotoxic effects. Therefore, the concentration of 20 mg L−1 EOLS is recommended for use in the transport of juvenile C. macropomum.