Photoreceptors. Cone cells. Tetrachromats. And why different species see different colors.
Colors are an important part of the gastronomical experience, influencing how delicious we think a food or drink is. They are also an important part of almost everything we see and do around us.We can see colors because of the cone cells in our eyes. More specifically, cone cells are one of the two types of light-sensitive cells known as photoreceptor cells in our eyes’ retina (the other type are rods, which are sensitive only to brightness and not colors, so don’t worry about them just yet).
We have three types of cones. One cone cell is sensitive to light of long wavelengths (red), another to medium wavelengths (green), and the third to short wavelengths (blue).
Red, green and blue are the three primary colors in the additive color model, and their combinations allow us to see all the colors in the visible part of the electromagnetic spectrum (read all about this in the 1-Minute NomNom “Colors!”). That’s pretty remarkable for just three cone cells. This makes humans trichromats.
What happens if our eyes had a fourth cone cell? Then according to Popular Science, we would be able to see 100x more colors and shades of colors! Anyone with four cone cells is called a tetrachromat. It is estimated that 1% of the world’s population are tetrachromats.
And what if our eyes had five or even six cone cells? That might very well make us butterflies! The papilio butterfly, for example, has six photoreceptor cells. That would mean butterflies can see colors that we do not even have names for. And what humans think are invisible, such as gamma rays, X-rays or radio waves, might very well be visible colors to butterflies.
The species with the most complex color vision is the mantis shrimp. According to The Oatmeal, the mantis shrimp has 16 cones! What it sees must be a psychedelic world on steroids (even its shell — see below — is a rainbow on steroids!).
At the other end of the spectrum, some species such as marine mammals have only one type of cone cells i.e. monochromacy. And other animals have two types of cone cells, making them dichromats. Dogs, for example, are dichromats. They have green cone cells and blue cone cells.
Keep that in mind the next time you throw a red ball and ask your doggie to fetch. What you see is not exactly what your pup sees. Or for that matter, what a butterfly, mantis shrimp, or even a tetrachromat friend sees!
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photos: in order – depositphotos/ewastudio; edesignua; Furian; Christian; fenkieandreas