title: Advantage of dichromats over trichromats in discrimination of color-camouflaged stimuli in nonhuman primates.
abstract: Due to a middle- to long-wavelength-sensitive (M/LWS) cone opsin polymorphism, there is considerable phenotypic variation in the color vision of New World monkeys. Many females have trichromatic vision, whereas some females and all males have dichromatic vision. The selective pressures that maintain this polymorphism are unclear. In the present study we compared the performance of dichromats and trichromats in a discrimination task. We examined tri- and dichromatic individuals of two species: brown capuchin monkeys (Cebus apella) and long-tailed macaques (Macaca fascicularis). We also examined one protanomalous chimpanzee (Pan troglodytes). The subjects' task was to discriminate a circular pattern from other patterns in which textural elements differed in orientation and thickness from the background. After they were trained with stimuli of a single color, the subjects were presented with color-camouflaged stimuli with a green/red mosaic overlaid onto the pattern. The dichromatic monkeys and the protanomalous chimpanzee selected the correct stimulus under camouflaged conditions at rates significantly above chance levels, while the trichromats did not. These findings demonstrate that dichromatic nonhuman primates possess a superior visual ability to discriminate color-camouflaged stimuli, and that such an ability may confer selective advantages with respect to the detection of cryptic foods and/or predators.
authors.affiliation: Department of Animal Models for Human Disease, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan. atsuko@ncnp.go.jp
authors.forename: Atsuko
authors.initials: A
authors.lastname: Saito
authors.forename: Akichika
authors.initials: A
authors.lastname: Mikami
authors.forename: Shoji
authors.initials: S
authors.lastname: Kawamura
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ueno
authors.forename: Chihiro
authors.initials: C
authors.lastname: Hiramatsu
authors.forename: Kanthi A
authors.initials: KA
authors.lastname: Widayati
authors.forename: Bambang
authors.initials: B
authors.lastname: Suryobroto
authors.forename: Migaku
authors.initials: M
authors.lastname: Teramoto
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Mori
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Nagano
authors.forename: Kazuo
authors.initials: K
authors.lastname: Fujita
authors.forename: Hika
authors.initials: H
authors.lastname: Kuroshima
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hasegawa
mesh_terms: D000818:Animals; D002428:Cebus / Q000235:genetics / Q000502:physiology*; D003118:Color Perception; D004193:Discrimination Learning; D005260:Female; D008251:Macaca / Q000235:genetics / Q000502:physiology*; D008297:Male; D002679:Pan troglodytes / Q000502:physiology*; D011110:Polymorphism, Genetic; D011930:Reaction Time; D014787:Vision Tests