Effects of analgesia on the response to a noxious stimulus in Norway lobsters (Nephrops norvegicus)

There is evidence that decapod crustaceans have the capacity to experience aversive states associated with nociception, highlighting the need for humane treatment. Behavioural and physiological responses to nociceptive stimuli may be reduced with analgesic drugs, yet little is known for decapods about effective options. In this study, the impact of electric shock on behaviour and physiology was investigated in Norway lobsters. Behaviour was monitored from before the shock to two hours after, with and without drugs with analgesic properties. Haemolymph and nervous tissues were analysed for stress indicators, including lactate, glucose, and gene expression. Electric shock induced tail flipping responses, absent in sham groups, however this was significantly reduced in animals treated with a local anaesthetic and an analgesic; suggesting these responses were mediated by nociception. Aspirin and lidocaine were effective at reducing this shock-related behaviour, however aspirin injection increased grooming immediately after administration, with elevated haemolymph lactate and downregulated gene expression in ganglionic tissues. Overall, the acute shock stimulus did not produce long lasting effects, but both drugs reduced tail flipping during shock. These results underscore the potential of these drugs for laboratory use during invasive procedures, but also the broader ethical responsibility to incorporate welfare strategies in crustacean handling and stunning protocols.