Research into pain and sentience in invertebrates — from crustaceans to insects and mollusks — is advancing rapidly and has direct implications for how we treat billions of animals.
Invertebrate pain research has transformed our understanding of which animals may be capable of suffering in ways that matter morally. The evidence is clearest for cephalopod mollusks (octopuses, squid, cuttlefish) — complex, intelligent animals whose cognitive sophistication is difficult to dispute. Decapod crustaceans have substantially growing evidence, culminating in regulatory recognition in the UK. Insects and other invertebrates represent a larger and more uncertain frontier where the precautionary principle increasingly applies given the scale of potential suffering involved. This research is not academic: billions of crustaceans, insects, and mollusks are boiled alive, ground up, or otherwise killed annually without any welfare consideration. As the evidence base grows, the welfare obligations to these animals grow correspondingly.