Assessment of Various Anesthetic Agents on Octopus vulgaris Paralarvae

Abstract

European Directive 2010/63 addresses the welfare of cephalopod species used in scientic projectsunder European jurisdiction and covers experimental procedures likely to cause pain, suffering,distress, or lasting harm. These procedures require authorization from the National CompetentAuthorities. In aquaculture research, some procedures require the temporary immobilization ofindividuals to allow for measuring body parameters (i.e., weight, sex, gonad condition, and others),avoiding any damage. This study compares three anesthetics used on common octopus, Octopus vulgaris,paralarvae to reach a state of sedation. The anesthetics were tested for their effects at differentconcentrations: magnesium chloride (6.8, 13.6, 20.4, and 27.4 g/L), ethanol (8, 10, and 12 mL/L), andclove oil (0.2, 0.3, and 0.4 g/L). Three variables were monitored: induction, recovery, and stressfulbehavior of paralarvae during treatments. Signicant differences were found between anesthetics,both in the induction and recovery time, and between concentrations of the same anesthetic. Theshortest times of induction and recovery corresponded to ethanol at low concentrations, 10 mL/L(20 ± 1 sec) and 8 mL/L (19 ± 2 sec), respectively. Clove oil at 0.2 g/L was the slowest to reachsedation (340 ± 7 sec). Magnesium chloride at 20.4 g/L showed longer recovery times (554 ± 201 sec)with increasing concentrations. Octopus paralarvae showed adverse behavior only under clove oiltreatments, whose use is therefore considered inadmissible. This study shows that ethanol at 10 mL/Lmay be suitable as a reliable anesthetic for octopus paralarvae, diminishing the induction and recoverytime without showing any stressful behavior.