Evolution of sensory systems underlies the emergence of predatory feeding behaviours in nematodes

Understanding how animal behaviour evolves remains a major challenge, with few studies linking genetic changes to differences in neural function and behaviour across species. Here, we identify specific sensory adaptations associated with the emergence of predatory feeding behaviours in the nematode Pristionchus pacificus. While Caenorhabditis elegans uses contact-dependent sensing primarily to avoid threats, Pristionchus pacificus has co-opted this modality to support both avoidance and prey detection, enabling context-dependent predatory behaviour. To uncover a potential mechanism underlying the evolution of P. pacificus prey perception, we mutated 27 canonical mechanosensory genes and assessed their function using behavioural assays, automated behavioural tracking, and a machine learning analysis of behavioural states. While several mutants showed mechanosensory defects, Ppa-mec-6 mutants specifically also impaired prey detection, indicating the emergence of a novel mechanosensory module linked to predatory behaviour. Furthermore, disrupting both mechanosensation alongside chemosensation revealed a synergistic influence for these modalities. Crucially, both mechanosensation and chemosensation pathways converge in the same environmentally exposed IL2 neurons, and silencing these cells induced severe predation defects validating their importance for prey sensing. Thus, predation evolved through the co-option of mechanosensory and chemosensory systems that act together to shape the evolution of complex behavioural traits.