A molecular phylogenetic tree of the opsin family. The tree was inferred by the neighbor-joining method . It shows that members of opsin family are divided into seven subfamilies, whose names are given on the right of the tree. Common names of species shown: Anopheles, mosquito; Branchiostoma, amphioxus; Ciona, ascidian; Drosophila, fruit fly; Patinopecten, scallop; Platynereis, polychaete annelid worm; Procambarus, crayfish; Schistosoma, blood fluke; Todarodes, squid. Abbreviations: LW, long-wavelength-sensitive opsin; SW, short-wavelength-sensitive opsin; MW, middle-wavelength-sensitive opsin; Rh, rhodopsin; RGR, retinal G-protein-coupled receptor. Other abbreviations are protein names; where only a color is given for a protein name, it refers to a cone opsin that detects that color.