Advantage of dichromats over trichromats in discrimination of color-camouflaged stimuli in nonhuman primates.
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.
Saito
Atsuko
A
Department of Animal Models for Human Disease, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan. atsuko@ncnp.go.jp
Mikami
Akichika
A
Kawamura
Shoji
S
Ueno
Yoshikazu
Y
Hiramatsu
Chihiro
C
Widayati
Kanthi A
KA
Suryobroto
Bambang
B
Teramoto
Migaku
M
Mori
Yusuke
Y
Nagano
Kunitoshi
K
Fujita
Kazuo
K
Kuroshima
Hika
H
Hasegawa
Toshikazu
T
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