Ancestral roots of immune priming in Papilionidae?

Immune priming refers to the enhanced protection exhibited by invertebrates upon a secondary immune challenge following a prior specific exposure. Although research on this phenomenon is advancing rapidly, its evolutionary origins and prevalence across lineages remain unclear. We investigated immune priming in Baronia brevicornis, considered the most basal extant member of the family Papilionidae. Primed caterpillars showed significantly higher survival after a bacterial challenge, as well as increased prophenoloxidase (proPO) activity and a marginal increase in phenoloxidase (PO) activity compared with controls. Antimicrobial activity did not differ between treatments. These results provide evidence of immune priming in this ancient butterfly lineage, suggesting that immune memory may have evolved early and diversified across Lepidoptera.