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

Understanding how animal behavior evolves remains a major challenge, with few studies linking genetic changes to differences in neural function and behavior across species. Here, we identify specific sensory adaptations associated with the emergence of predatory feeding behaviors in the nematode Pristionchus pacificus. While Caenorhabditis elegans uses contact-dependent sensing primarily to avoid threats, P. pacificus has co-opted this modality to support both avoidance and prey detection, enabling context-dependent predatory behavior. To uncover a potential mechanism underlying the evolution of P. pacificus prey perception, we mutated 27 canonical mechanosensory genes and assessed their function using behavioral assays, automated behavioral tracking, and a machine learning analysis of behavioral states. While several mutants showed mechanosensory defects, Ppa-mec-6 mutants specifically also impaired prey detection, indicating the emergence of a mechanosensory module linked to predatory behavior. Furthermore, disrupting both mechanosensation alongside chemosensation revealed a synergistic influence for these modalities. Crucially, Ppa-mec-6 is expressed in the environmentally exposed IL2 neurons that represent the first point of predator-prey contact. Moreover, silencing Ppa-mec-6 expressing 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 behavioral traits.