Tetrachromacy

Tetrachromacy (from <a href="/facts/Ancient_Greek/LIK7NlUh">Ancient Greek</a> tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying <a href="/facts/Color/XDvW7ESP">color</a> information, or possessing four types of <a href="/facts/Cone_cell/JoQeEzoF">cone cell</a> in the <a href="/facts/Eye/h3lbYU55">eye</a>. Organisms with tetrachromacy are called tetrachromats.
In tetrachromatic organisms, the sensory <a href="/facts/Color_space/zFvEyfHv">color space</a> is four-dimensional, meaning that matching the sensory effect of arbitrarily chosen spectra of light within their <a href="/facts/Visible_spectrum/frPBh8o5">visible spectrum</a> requires mixtures of at least four <a href="/facts/Primary_color/F4wNk0TC">primary colors</a>.
Tetrachromacy is demonstrated among several species of <a href="/facts/Bird_vision/LVKYqEu7">birds</a>, <a href="/facts/Fish/fln4gH9V">fishes</a>, and <a href="/facts/Reptile/04n1uKf1">reptiles</a>. The common ancestor of all <a href="/facts/Vertebrate/tT54FSTT">vertebrates</a> was a tetrachromat, but a common ancestor of <a href="/facts/Mammal/phSwTzBo">mammals</a> lost two of its four kinds of cone cell, evolving <a href="/facts/Dichromacy/19kYX4mk">dichromacy</a>, a loss ascribed to the conjectured <a href="/facts/Nocturnal_bottleneck/zBvv1mNd">nocturnal bottleneck</a>. Some <a href="/facts/Primate/Hl8RNE2X">primates</a> then later evolved a third cone.

Tetrachromacy open-in-new

Tetrachromacy