Assessing Local Anesthesia in Octopus bimaculoides to Provide Analgesia

Despite the substantial growth of cephalopod research over the past 15 years, effective pain management for these animals remains largely unstudied, and no US federal regulations currently address cephalopod analgesia. This 2-phase study evaluated the feasibility and efficacy of lidocaine, bupivacaine, and extended-release bupivacaine injections for producing analgesia in juvenile Octopus bimaculoides in an established model of arm regeneration. Phase I served as a pilot to assess adverse effects, practicality, and histopathologic consequences of drug administration. Forty-nine animals were randomized to the saline control or treatment groups. Phase II assessed lidocaine, bupivacaine, and saline in an additional 34 animals, using behavioral metrics at multiple time points, including a posture and gait analysis during a walking assessment and mechanical allodynia evaluation via the von Frey filament test. Health indicators, such as weight change and respiratory rate, were also monitored. Finally, wound healing and arm regeneration were followed with photo documentation. Although all animals displayed statistically significant changes in arm posture and gait immediately postsurgery, these changes invariably resolved within 72 hours irrespective of treatment group. Moreover, health and regenerative outcomes did not differ significantly among the treatment groups. The failure of local anesthetic efficacy highlights the need for alternative analgesic regimes for octopus research.