The diversity of invertebrate visual opsins spanning Protostomia, Deuterostomia, and Cnidaria

Across eumetazoans, the ability to perceive and respond to visual stimuli is largely mediated by opsins, a family of proteins belonging to the G protein-coupled receptor (GPCR) superclass. Lineage-specific gains and losses led to a striking diversity in the numbers, types, and spectral sensitivities conferred by visual opsin gene expression. Here, we review the diversity of visual opsins and differences in opsin gene expression from well-studied protostome, invertebrate deuterostome, and cnidarian groups. We discuss the functional significance of opsin expression differences and spectral tuning among lineages. In some cases, opsin evolution has been linked to the detection of relevant visual signals, including sexually selected color traits and host plant features. In other instances, variation in opsins has not been directly linked to functional or ecological differences. Overall, the array of opsin expression patterns and sensitivities across invertebrate lineages highlight the diversity of opsins in the eumetazoan ancestor and the labile nature of opsins over evolutionary time.

Automated summary

This article reviews the diversity of visual opsins and differences in opsin gene expression in different animal groups. The study reveals significant variations in the numbers, types, and spectral sensitivities of visual opsins across lineages. The functional significance of opsin expression differences and spectral tuning among lineages is discussed. Some cases show that opsin evolution is linked to the detection of specific visual signals, while in other cases, variation in opsins is not directly related to functional or ecological differences. Overall, the diversity of opsin expression patterns and sensitivities in invertebrate lineages highlights the variability of opsins over evolutionary time.