Wound-induced reactivation of developmental cuticle programmes in mature insects

The insect cuticle exoskeleton is among the most abundant and versatile biological structures. During ontogeny, the cuticle undergoes extensive modification, enabling insects to adapt to a wide range of ecological niches. In contrast, cuticular remodelling is generally thought to cease after adult emergence, raising the question of how mature insects respond to damage to their exoskeleton. To address this fundamental issue, we used an interdisciplinary experimental approach combining biomechanics, quantitative image analysis and molecular biology to investigate the response of mature Locusta migratoria to cuticular injury. We show that deep tibial wounds penetrating the epidermis trigger a coordinated repair programme that integrates rapid sclerotization of the perilesional cuticle with the local deposition of newly synthesized, layered cuticle beneath the wound site. These structural responses are accompanied by a strong but transient reactivation of the developmental enzyme chitin synthase 1 and the induction of the antimicrobial peptide defensin 3 in the vicinity of the injury. In contrast, superficial injuries that do not reach the epidermis fail to elicit cuticle deposition and sclerotization. Together, our results demonstrate that mature insects retain the capacity to locally reactivate developmental cuticle pathways to restore exoskeletal integrity, thereby directly linking structural repair with immune activation.