Mantis Shrimp’s Bizarre Eyesight Finally Figured Out

By Breanna Draxler | January 23, 2014 1:08 pm
mantis shrimp

Juvenile mantis shrimp. Image credit: Roy L. Caldwell

Mantis shrimp have a type of vision unlike any other animal on the planet—that much was known. But now scientists have determined, at a cellular level, how it is that these foot-long crustaceans see the world. And it stems from their unique photoreceptors.

In general, photoreceptors absorb light and convert it into electrical signals, which are then sent to the brain for interpretation. Each photoreceptor is specific to a particular wavelength of light, which the brain translates into a color. Your dog has two kinds of photoreceptors: blue and green. You have three: blue, green and red. Our eyes can see these colors and every combination or variation thereof.

Scientists say that in order to see every color under the sun, an animal needs four to seven different types of photoreceptors. Why, then, does the mantis shrimp have a whopping 12 different kinds of photoreceptors in their eyeballs?

Seeing Colors

The researchers say it’s because mantis shrimp photoreceptors work in a unique way, completely unlike like the rest of ours.

Researchers reached this conclusion after playing a reward game with mantis shrimp. They would shine two different colored lights simultaneously at the shrimp. Pinching their claws at the source of one color, let’s say yellow, would result in the shrimp getting a treat. Choosing the blue one meant no treat. This drill was repeated until the shrimp learned to pick the yellow light and were able to do so consistently. Then the researchers began to switch the other colors up, making the shrimp choose between red and yellow, then orange and yellow, etc.

Surprisingly, when the colors got too close to one another (i.e. yellow and a shade of orange akin to macaroni and cheese) the shrimp couldn’t tell them apart. Even with their 12 kinds of photoreceptors, shrimp could only distinguish colors on the light spectrum that were at least 25 nanometers apart. By comparison, humans, with a measly three kinds of photoreceptors, can distinguish colors separated by as little as one nanometer.

Fast Processing

From this the researchers deduced that the mantis shrimp’s whole visual system operates differently than our own. As they describe in their paper published in Science today, further investigation showed that shrimp don’t take the time to send visual information to the brain and wait for it to distinguish between subtle color differences like we do. The shrimp just skips over this step altogether.

Each of the shrimp’s 12 photoreceptors is essentially set to a different sensitivity. Their eyes scan a scene and are able to instantly recognize when something falls into its reddish category, without having to ask their brain if it’s seeing brick red or scarlet. In the colorful and fast-paced circus that is its coral reef home, avoiding that little bit of a processing delay could be the difference between life and death, even for a foot-long crustacean.

The same goes for their dinner. This unique kind of vision could be a mantis shrimp’s hidden weapon in capturing prey—well, alongside its ability to swing its front claws at the speed of a .22 caliber bullet to bludgeon, spear or dismember an unwitting victim.

If you want to gaze deep into these crazy eyes (not to mention witnessing a mantis shrimp’s eye-grooming techniques!) check out this video. Dramatic mood music included.

Video credit: Mike Bok

CATEGORIZED UNDER: Environment, Mind & Brain, top posts
  • michaelvacirca

    sounds like their GPU unit is right next to the I/O rather than doing a callback to the CPU :)

    • iamthepiguy

      So basically, they’re using GPGPU for visual processing.

    • krell51

      Actually that is similar to an Ai system that I was thinking of for a robot, where this various systems do their own processing, visual, hearing, ballence and movement without having to involve the main processor. It sees a shape, determines the shape is a chair 5′ away then tells the main system “chair at 5′ in this direction. ” The main system isn’t bothered with taking time to decide what the shape is.

  • mimi

    ooh poor shrimp, what art this humans doeth to thou

    • Nick Whiley

      To THEE. Grammar, please. ;)

      • andrewwiggin

        Grammar, indeed. ‘Doeth’ is third person singular and ‘art’ is second person singular. A grammatical phrasing might be “Alas, poor shrimp, thy fate’s a drear one. What have these humans done to thee? Strike with thy mighty claws to lay them low!”

  • http://obbop.wordpress.com/ obbop

    All I care about is if they are tasty when cooked.

  • Cynthia Ivey

    Why would evolution evolve their eyes as such only to not be able to utilize there full potential? Thats not logical.

    • David Waring

      Evolution is not “logical’ in the sense that it always works in the best or most efficient way. Evolution is based on random changes and selection so sometimes things evolve in ways that appear illogical, but still provide selective advantage.

    • Renee

      The advantage conferred is speed over precision. They can’t tell the difference between slight shades of orange, but they can react more quickly. That’s definitely a bigger survival advantage in that environment, so it is entirely logical if you’re a mantis shrimp.

      • colindenronden

        They don’t eat macaroni cheese, they only end up on the pizza.

    • http://blogs.discovermagazine.com Longmire

      Looks like “evolution” took a hit of acid, got creative, saw how overwhelming it was to perceive then dumbed it down a bit for its progeny.

  • Douglas J. Bender

    Given their awesome punching power, I wonder why no sports team is named “The Mantis Shrimps”.

    • Don’t Even Try It!

      It kind of gives a whole new meaning to the word “shrimp”!

  • Utica

    … the eyes move in different directions at the same time… allowing them greater latitude…a bigger field of vision… depth perception in each eye could be independent… our field of vision is extremely limited… we could not process the information obtained… no nerves for it…

  • Alexis Silvaggio

    Wow so cool!!!!

  • Tom Pace

    Isn’t it possible that the fine detail resolution of the received world image from the photo receptors be affected within the eye or environment? Such as a shrimp that needs glasses… heh heh. Anyway this sounds very fun to research. Also reminds me of another Discover article about some humans with 4 types of photoreceptors, July/August 2012.

  • CmdrAdobo

    This creature is tasty. Lots of fisherman in Cebu selling them.

  • http://blogs.discovermagazine.com Rick Bernal

    I was wondering what the black spots are on their eyes.

  • http://www.ashleyhauck.com Ashley Hauck

    So their eyes are highly developed so their brains don’t have to be?

  • Alicia Norman

    Crazy looking yet somehow still quite lovely.

  • jock christopher

    chuckles,magnificent.

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