Lippia alba and Aloysia triphylla essential oils are anxiolytic without inducing aversiveness in fish

Lippia alba and Aloysia triphylla essential oils (EOs) are known to contain anesthetic properties. The majority of conventional anesthetics applied to fish cause aversive behavior in these animals. Therefore, questions arise whether EOs from L. alba and A. triphylla are also aversive and if they alter anxioly-like behaviors. To answer these questions, jundiá (Rhamdia quelen) and zebrafish (Danio rerio) were studied with the preference test using 50% of the anesthetic concentration of L. alba (corresponding to 150 μL L− 1) and A. triphylla (corresponding to 150 μL L− 1) EOs and the novel tank test immediately after exposure. Cortisol analysis was also performed. We show that EOs from L. alba and A. triphylla have an anxiolytic effect on zebrafish and catfish without altering locomotor patterns or inducing aversive behavior. To the best of our knowledge, this was the first time that preference tests were applied for natural anesthetics from plant extracts.