In search of an effective and safe anesthetic in decapod crustaceans: Insights from Procambarus clarkii

This study evaluates the effectiveness of different anesthetic compounds in the red swamp crayfish, Procambarus clarkii , a species of major commercial importance. The study addresses the growing need for improved welfare standards in crustacean aquaculture by assessing how anesthetics can mitigate the physiological and behavioral stress responses resulting from handling. We first characterized the acute stress response in crayfish after a 5-min air exposure, observing significant changes in hemolymph pH, lactate, chloride, and hemocyanin. Next, we tested the efficacy of several anesthetic/sedative agents, including 2-phenoxyethanol, ethanol, tricaine methanesulfonate (MS-222), clove oil, ketamine, and xylazine. We found that 2-phenoxyethanol, ethanol, and MS-222 were ineffective in inducing deep anesthesia. In contrast, clove oil (0.5 mL L −1 ), ketamine (50 μg g −1 ), and xylazine (15 μg g −1 ) were effective, with each showing distinct induction and recovery times. Physiological analysis one hour after anesthesia revealed that xylazine treatment significantly increased hemolymph lactate, as seen after an acute stress. Similarly, in an open-field test, xylazine-treated crayfish showed reduced time close to the wall, consistent with a putative anxiolytic effect. Ketamine appears to delay full recovery, showing signs of sedation one hour after anesthesia. In summary, our findings suggest that clove oil is a valid anesthetic for P. clarkii , as it induces deep anesthesia with a rapid recovery while effectively mitigating stress-related physiological responses. This study provides a foundational protocol for improving the welfare of decapod crustaceans in aquaculture and research through the use of anesthetics.