Understanding how pain works across different animal groups - from vertebrates to invertebrates - is essential for setting appropriate welfare standards and protections.
Pain neuroscience provides empirical foundations for animal welfare ethics. The discovery that fish use opioid-based pain pathways and respond to analgesics was pivotal in driving regulatory change - the Animal Welfare Act's extension to vertebrates, and the UK's inclusion of decapod crustaceans and cephalopods in its Animal Welfare (Sentience) Act 2022. Research frontiers include invertebrate pain mechanisms, the relationship between nociception and subjective suffering, and species-specific analgesic needs in veterinary and farm contexts. Each advance has direct policy implications.