Arthropod Corneal Nanocoatings: Diversity, Mechanisms, and Functions

Abstract

Corneal surfaces of terrestrial insects and other arthropods are covered with elaborate nanocoatings. Initially described as moth-eye nanostructures-paraboloid nipple-like evaginations regularly assembled on the lenses of some Lepidopterans-they were in recent years discovered to be omnipresent across insect lineages. In addition to the nipple-type morphology, corneal nanocoatings can be built as ridge-, maze-, or dimple-type nanopatterns, with various transitions among these morphologies seen in different species or even within the same specimen. Varying in the height of dozens to hundreds nanometers, and in the diameter being thinner than the wavelength of the visible light, these nanostructures provide the antireflective function to the surfaces they coat. Additional functionalities, such as water-repelling, antifouling, or antibacterial, could also be attributed to them. Turing reaction-diffusion and the block copolymerization mechanisms of molecular self-assembly have been proposed to guide the formation of corneal nanostructures during insect eye development. Both mechanisms envision interactions of two types of molecular agents with different diffusion and/or hydrophobicity properties as the underlying principle of building of the nanostructures. Using model insect organisms , the molecular identities of these agents can be revealed. These studies will