Color vision in butterflies is dependent upon the presence of different photoreceptor neurons within the retina, which are sensitive to different colors of light. Just as in many vertebrate and invertebrate species, this results from the highly regulated expression of different forms of the light sensitive visual pigment rhodopsin, in different types of photoreceptor cells. During evolution, gene duplication events have produced numerous forms of rhodopsin in different species. The PIs will study this evolutionary process and the origin of the different forms of rhodopsin. The PIs will examine the rhodopsins of the Tiger Swallowtail butterfly (Papilio glaucus) as well as those of more distantly related species. The PIs will measure the colors of light absorbed by the different butterfly rhodopsins and determine which specific photoreceptor cells within the retina express each form of rhodopsin. The PIs will also compare the amino acid and nucleotide sequences of these and other rhodopsins to determine whether the rhodopsins absorbing the same wavelengths of light are likely to have evolved from a common ancestral gene or if they may have evolved independently. These studies will clarify the evolutionary mechanisms by which color vision was established, and contribute to the basic knowledge of the visual system of insects.