The evolution of red color vision is linked to coordinated rhodopsin tuning in lycaenid butterflies

Abstract

Significance Opsins are photosensitive receptors capturing specific wavelengths of incoming light to convey color vision across animals. Lack of reliable expression systems to study invertebrate G q opsins has limited our ability to tease apart genotype–phenotype relationships underlying spectral tuning and visual adaptations in insects compared to homologous yet phylogenetically distant vertebrate G t opsin lineages. We developed a robust method to express invertebrate opsin proteins in vitro, which we apply to study the visual system of a lycaenid butterfly. Our detailed molecular characterization of red-shifted long-wavelength and duplicate short-wavelength G q insect opsins, together with a broad mutagenesis approach for exploring invertebrate opsin sequence-visual pigment functions, begins pinpointing the proximate evolutionary mechanisms underlying the diversification of color vision systems across animal life.