Trichromacy

From Wikipedia, the free encyclopedia

Trichromacy is the condition of possessing three independent channels for conveying colour information, derived from the three different cone types.^[1] Organisms with trichromacy are called trichromats.

The normal explanation of trichromacy is that the organism's retina contains three types of colour receptors (called cone cells in vertebrates) with different absorption spectra. In practice the number of such receptor types may be greater than three, since different types may be active at different light intensities. In vertebrates with three types of cone cells, at low light intensities the rod cells may contribute to colour vision, giving a small region of tetrachromacy in the colour space.

Humans and other closely related primates are usually trichromats, as are female New World monkeys of most species, and both male and female howler monkeys. Recent research suggests that trichromacy may also be quite general among marsupials. Most other mammals are currently thought to be dichromats, with only two types of cone (though the possibility of limited trichromacy at low light levels where the rods and cones are both active). Some species of insects (such as honeybees) are also trichromats, being sensitive to ultraviolet, blue and green instead of blue, green and red.

[edit] See also

• Trichromatic color vision
• Tetrachromat

[edit] References

• Arrese, CA; Oddy, AY; Runham, PB; Hart, NS; Shand, J; Hunt, DM (2005). "Cone topography and spectral sensitivity in two potentially trichromatic marsupials, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus)." Proceedings of the Royal Society of London Series B. 272(1595), 791-796.
• Calderone, JB; Jacobs, GH (2003). "Spectral properties and retinal distribution of ferret cones." Visual Neuroscience. 20(1), 11-17.
• Calderone, JB; Reese, BE; Jacobs, GH (2003). "Topography of photoreceptors and retinal ganglion cells in the spotted hyena (Crocuta crocuta)." Brain Behavior and Evolution. 62(4), 182-192.
• Rowe, Michael H (2002). "Trichromatic color vision in primates." News in Physiological Sciences. 17(3), 93-98. [1]

[edit] External links

• The Straight Dope: "Are cats and dogs really color-blind? How do they know?"