Research summary - The evolution of nociception in arthropods (Rethink Priorities)

Executive Summary

Goldberg et al. (2024) sequenced the Chinese mantis genome to investigate whether mantids possess nociceptive ion channels—genes enabling animals to sense harmful stimuli. This challenges Eisemann et al.'s (1984) classic argument that male mantids' continued mating during sexual cannibalization demonstrates insects lack pain sensation.

Key Findings:

• Chinese mantids possess genes encoding nociceptive ion channels for mechanical, thermal, and chemical damage detection, contradicting the assumption that mantids cannot sense noxious stimuli.

• Survey of 40 arthropod genomes (mostly insects, plus chelicerates and decapods) reveals nociception genes are widespread and evolutionarily conserved, with most insects having 6-7 of the gene families surveyed.

• All examined farmed arthropods (shrimp, black soldier flies, mealworms, crickets, honey bees, silkworms) possess the majority of nociceptive ion channel categories in their genomes, suggesting domestication does not eliminate nociceptive capacity.

• The most frequently absent gene in farmed species was Pkd2 (associated with cold nociception), though other cold-sensing genes remain present. No category of typically noxious stimuli can reasonably be expected to be non-noxious for farmed insects.

Implications:

The genetic evidence makes alternative explanations for mantid sexual cannibalization behavior more plausible than lack of pain perception. For farmed insects, understanding which nociceptors are present could inform welfare standards regarding environmental conditions, stunning methods, and slaughter practices. Further anatomical and functional studies are needed to confirm gene expression and nociceptive function.