Four hundred million years after hacking its own evolutionary path out of the Cambrian, the mantis shrimp is one of the world's freakiest animals.

How freaky? Well, it sees something called circular polarized light – a form of light that no other creature on Earth can perceive.

This newly discovered ability was described in a study published yesterday in Current Biology, and if you're interested in the mechanics of mantis shrimp eyes and the properties of circular polarized light, then head on over to my Wired.com news article.

I note in the article that understanding the shrimps' ability to see

CPL could help engineers refine high-tech communications systems that make use of the light's loss-free spin.

But let's be real – this discovery wasn't cool because it'll someday help people download Rihanna songs on their cell phones or watch *Your

Mama Don't Dance *in extra-high definition. It was cool because no other animal sees circular polarized light. The mantis shrimp single-clawedly expands the realm of possible visual perception by thirty-three percent.

(The other types of sight are black-and-white, color and linearly polarized.)

Tom Cronin – who, along with co-authors Justin Marshall and Roy

Caldwell, is the world's foremost expert on mantis shrimp vision – didn't dismiss the biomimetic applications in so many words, but it was clear when we talked that he wasn't too excited about them. Sure, the Air Force funds his University of Maryland, Baltimore County lab's

research, and maybe their wonks will do something practical with his insights, and that would be great – but he's not especially concerned about it.

(To be fair, Justin Marshall seemed a little more excited about the applications – but even his invocation of CPL in skin cancer detection carried a whiff of the obligatory.)

As became clear when Cronin finished explaining CPL

and started talking about the animal, what gets these guys to the lab in the morning is the mantis shrimp itself.

"They're enchantingly violent," he said in an affectionate, almost paternal tone. "They catch other animals by either spearing it through the heart or smashing it to pieces. Unlike most predators that grab prey, these pummel it and destroy it. When they interact with each other over a burrow, they use their armored front appendages and smash each other on the face. Whenever they get into any type of situation, they smash things. You can't pick these up. They're really great animals to have around."

Cronin seemed especially pleased that the shrimps' visual uniqueness would return them to the record books. "The movement they use to hit prey used to be the fastest movement made by any animal," he lamented. "But it turned out there was a jaw-snapping behavior in an ant that's even faster."

So why did they evolve to see CPL? Who knows. Cronin noted that some species have a CPL-reflecting patch on their tail, which they use to signal each other while negotiating mates or territory – but there are plenty of other ways to do this. Then again, when you and your possible opponent are so fundamentally bash-inclined, it makes sense to keep every possible communication channel open.

And channels the mantis shrimp has in abundance. Though CPL-sight is their greatest claim to optical fame, their eyes are chock full of weird cells and structures that let them distinguish between no fewer than 100,000 colors – ten times more colors than we can see.

Cronin called mantis shrimp eyes an outstanding system for studying the principles of visual evolution. But even that strikes me as a non-utilitarian purpose. Maybe someday scientists will make cybernetic optical implants that let me see a few thousand more colors – but until then, understanding the eye's evolution isn't so much a material application as a spiritual one. Knowledge is a fundamentally good thing: learning more about the world is intrinsically valuable, because it adds that much more depth and nuance and color to our experience of life.

So why do mantis shrimp – which followed a solitary evolutionary trajectory out of the Cambrian, developing a physiology so weird that scientists called them "shrimps from Mars" – have such marvelous eyesight?

"One idea is that the more complicated your sensory structure is, the simpler your brain can be," said Cronin. "If you can deal with analysis at the receptor level, you don't have to deal with that in the brain itself."

There you have it: the world's most sensitive eyes allow them to be

simple! And smash things! And it's worked for 400 million years.

Circular Polarization Vision in a Stomatopod Crustacean [Current Biology]

Shrimp Eyes May Hold Key to Better Communications [Wired]

Image: Justin Marshall

*

Note: Mantis shrimps aren't actually shrimps or mantids – they just look like them. They're actually stomatopods.*

See Also:

WiSci 2.0: Brandon Keim's Twitter and Del.icio.us feeds; Wired Science on Facebook.