Researchers from Tokyo Metropolitan University have proposed a hypothesis to explain the rarity of insects in marine environments by examining their unique shell hardening mechanism. The enzyme multicopper oxidase-2 (MCO2) plays a crucial role in this process, allowing insects to use molecular oxygen for hardening their shells. This adaptation gives insects an advantage on land, where oxygen is plentiful, but creates disadvantages in ocean environments, which are less hospitable due to lower oxygen levels and the presence of better-adapted organisms like crustaceans. Unlike insects, crustaceans harden their shells using calcium from seawater, showing different adaptations to their environments.
The researchers highlighted that as insects evolved from marine ancestors to terrestrial habitats, the unique properties conferred by MCO2 enabled them to develop lightweight and protective cuticles, facilitating abilities like climbing, gliding, and flying. These capabilities have led to their ecological success and diversity on land. The study posits that without MCO2, the evolution and success of insects in terrestrial ecosystems might not have occurred, emphasizing the significance of cuticle hardening in insect evolution and adaptation. The research represents a new perspective on the ecological roles and evolutionary pathways of insects.
