Evolution of visual opsin genes in Trichoptera

Insects have evolved complex and diverse visual systems controlled by light-sensing molecules, known as opsins. Insect visual opsins group into three major clades based on wavelength sensitivity. These clades are known as long wavelength (LW), short wavelength (SW), and ultraviolet wavelength (UV) visual opsins. In addition, many insect species possess a non-visual opsin, named Rh7, whose function is not fully understood. While opsins in some insect groups have been studied well, opsins in caddisflies (Insecta: Trichoptera) have never been studied. Here, we found and used 59 caddisfly opsin sequences across 27 genomes to determine the phylogenetic relationships of opsin genes in Trichoptera. We found that there has been a loss of the SW opsin in all the species of Trichoptera in this study. In addition, a copy of the UV and Rh7 opsins were found in some, but not all, of the species. Lastly, we found great diversity in the occurrence and phylogenetic relationships in the LW opsin among different Trichoptera species. The findings of this study provide insight into the diversity of opsins in caddisflies and form a basis for further research of the evolutionary drivers and complexity of visual systems in Trichoptera.