An illustrated physiology of nervous systems in invertebrates

Abstract

Invertebrate sentience is crucial to understand due to the vast number of invertebrates in the wild and those used by humans. While definitive determination of sentience requires understanding consciousness, which remains elusive, nervous system structures offer indicators. Centralization, particularly structures enabling information processing, is a key indicator, alongside other factors like nervous system size and behavioral indicators of learning and memory. This work examines nervous system features across invertebrate phyla, including Cnidaria, Echinodermata, Nematoda, Platyhelminthes, Annelida, Mollusca (Bivalvia, Gastropoda, Cephalopoda), and Arthropoda (Insecta, Crustacea). Despite diverse nervous system structures, varying degrees of centralization are observed, suggesting the potential for sentience across many invertebrate groups. This potential is particularly evident in cephalopods with complex nervous systems, but even simpler systems like those in bivalves cannot exclude the possibility of sentience. The overview highlights the potential for diverse nervous systems to support sentience in invertebrates, although further research into the physiological basis of consciousness is needed. – AI-generated abstract.