Pain and stress in crustaceans?

We consider evidence that crustaceans might experience pain and stress in ways that are analogous to those of vertebrates. Various criteria are applied that might indicate a potential for pain experience: (1) a suitable central nervous system and receptors, (2) avoidance learning, (3) protective motor reactions that might include reduced use of the affected area, limping, rubbing, holding or autotomy, (4) physiological changes, (5) trade-offs between stimulus avoidance and other motivational requirements, (6) opioid receptors and evidence of reduced pain experience if treated with local anaesthetics or analgesics, and (7) high cognitive ability and sentience. For stress, we examine hormonal responses that have similar function to glucocorticoids in vertebrates. We conclude that there is considerable similarity of function, although different systems are used, and thus there might be a similar experience in terms of suffering. The treatment of these animals in the food industry and elsewhere might thus pose welfare problems.