The evolution of the green-light-sensitive visual opsin genes (RH2) in teleost fishes

•Teleost fishes have evolved multiple RH2 opsin genes via gene duplications.•A conserved synteny of the RH2 gene clusters is found across many teleost lineages.•The RH2 cone opsin gene is expressed in the retina of most teleost fish lineages.•RH2 is often the only cone opsin left in the blue-green light-dominated deep sea.•A green-shifted LWS copy functionally compensates the few cases where RH2 is lost.