What The Oatmeal Might Have Gotten Wrong About Mantis Shrimp

OdontodactylusScyllarusMantis shrimp are amazing little creatures. I was delighted to write about their superfast punch in a story last year. And that punch was one of the highlights in a fabulous online comic published by The Oatmeal yesterday, titled “Why the mantis shrimp is my new favorite animal.” But before getting to the punch, the comic discusses the critter’s vision. Here’s a sampling of what it says (minus the illustrations):

Our eyes contain millions of light sensitive cells, called rods and cones. Rods enable us to see light and motion. Cones enable us to see color….

When it comes to color vision, butterflies are almost the top of the food chain. There is one animal that has better vision than the butterfly: the mantis shrimp.

…this marvelous creature has not two, not three, not five, but sixteen color-receptive cones. The rainbow we [humans] see stems from just three colors, so try to imagine a mantis’ rainbow created from sixteen colors. Where we see a rainbow, the mantis shrimp sees a thermonuclear bomb of light and beauty.

This makes for a very pretty comic, but it may not be quite true, as demonstrated by a color test that was given to one mantis shrimp species, Haptosquilla trispinosa. The test, which was described in Science News last year, was carried out by Hanne Thoen, of the University of Queensland in Brisbane, Australia, who presented her results at a scientific meeting in Maryland:

Thoen tested the color vision of mantis shrimp by training them to scoot out of their burrows toward a pair of optical fibers and punch at the one glowing a particular color. As she narrowed the color gap between the two fibers, she could tell when the animals no longer discerned a difference.

People can distinguish some colors that are only a nanometer or two different. But mantis shrimp “flunked” this color test when the colors were 15 nanometers apart. So on a test like this, human vision might actually be better than that of mantis shrimp.

Researchers are still working out the reasons why the mantis shrimp might not be as discerning as we are when it comes to color, but brainpower might explain it. From Science News:

People and other animals studied so far distinguish colors through brainpower by interpreting competing activity in different kinds of light-receptor cells. Instead of doing such fancy brainwork, mantis shrimp may just rely on what a particular specialized cell responds to strongly. Wavelengths that tickle the purple-sensitive cells may be just plain purple regardless of whether they’re more toward the blue or the ultraviolet.

This was only one simple test of one species, and scientists are still figuring things out, so we can’t say for certain that mantis shrimp don’t have amazing vision. But humans also beat the shrimp in another area of sight, because the invertebrates aren’t great at seeing light in the red range. Those are the first wavelengths absorbed by water, so there’s not much need for cells to detect a color that doesn’t exist in their world. The wavelengths they can detect can vary, however. Scientists have found that mantis shrimp can tune their vision to the environment they grow up in, so those that live in shallow water will see different colors than those from the deep.

One place that the shrimp definitely have us bested in terms of vision, though, is ultraviolet — at those wavelengths, they can see things we never will. Whether that means the mantis shrimp can see a “thermonuclear bomb of light and beauty,” well, it’s hard to tell. But they certainly are beautiful, awesome creatures nonetheless.

Image of a mantis shrimp (Odontodactylus scyllarus) courtesy of Silke Baron, via wikimedia commons

9 thoughts on “What The Oatmeal Might Have Gotten Wrong About Mantis Shrimp

  1. Pingback: Morsels for the mind – 12/4/2013 | Six Incredible Things Before Breakfast

  2. I think it’s safe to say that you’re the first person in history to have described The Oatmeal as a “very pretty comic”…

    To be fair, however, they can still see more colors than we can, just less granularity, so The Oatmeal isn’t completely wrong…

    • There is no evidence that they can see more colors than us. Different ones, yes. A larger number of colors, maybe not.

      Their receptors covering a wider range of the EM spectrum doesn’t translate to more colors. Depends on what their brains do with the output of those receptors. If their processing is as basic as it seems, they probably see fewer colors.

      Too many people equate wavelength to color. The colors that are evoked by a single wavelength are called spectral colors and they form only a small part of all colors we are able to perceive. Maybe it would be better to think of spectral colors as hues, although that doesn’t really nail it either. Magenta is a hue, after all, but no spectral color.

  3. Well, from what I’ve read, their receptors act as multiple dichromatic units, and indeed, they work into UV, but because they’re dichromatic units, they can’t have the color discrimination that birds, reptiles, fish, and insects have…

  4. I was discussing this with a friend recently.
    So if they have 16 color receptors, can they see colors we can’t imagine? Or are they just more able to distinguish between the existing colors?
    But I also’d like to know about our spectrum of light – isn’t it just as flawed as we are, because we are human beings trying to make sense of the outside world? And if we only possess 3, what happens if we come into contact with a, say, an alien race of people that have 16? Would they find our art boring, siting that they are all just the same few colors, while we look at theirs and see no difference? Or would they see hundreds of colors where we only saw a few?
    I don’t think a color exists that only this alien race of people would have material made of, so I don’t think any human being is going to discover a new color from this alien race, but what would happen?

    • They have 12 color receptors. The others are for polarization vision, I think. Also, no, read this blog post again. Newer experiments have shown that mantis shrimp color vision isn’t that great. Not a big surprise, actually, because color happens in the brain. Don’t make the mistake of confusing wavelength with color, they are not the same. By the way, we possess 4 photoreceptor types, a few people apparently even 5 (you forgot to count our rods).

      Since color is a perception, not a physical thing, it is difficult to answer these questions. To quote Erwin Schrödinger (yes, the one with the cat):

      “The sensation of color cannot be accounted for by the physicist’s objective picture of light-waves. Could the physiologist account for it, if he had fuller knowledge than he has of the processes in the retina and the nervous processes set up by them in the optical nerve bundles and in the brain? I do not think so.”

    • That article is from 2008, but as this blog post repots, newer experiments have shown that mantis shrimp color vision isn’t as great as expected and previously claimed.

  5. I have a theory that the mantis shrimp is down-sampling contrast a bit due to the exponential increase in neural energy requirements that result from each additional color perceived due to the partly due to the combinations of said colors.

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