For a guy who goes by the handle “The Quantum Biologist,” I sure don’t talk much about physics. So as an example of physics in biology, I present one of the most fantastic creatures in natural history, the Mantis Shrimp. I would say it’s almost too awesome for this world, except that I think the world is so awesome. The world is awesome, and the Mantis Shrimp is irrefutable proof.
The Mantis Shrimp is not a shrimp, and he will beat you senseless if you call him one. He’s a stomatopod, an order of crustaceans who resemble an unholy hybrid of space aliens and Chinese dragons. (Or maybe dragon rolls?) Generally solitary, often monogamous, and always spoiling for a fight, the mantis shrimp lives in burrows it excavates beneath corals, where it lurks in wait for some snot-nosed crab to walk by. Mantis shrimp have a few claims to fame in the animal kingdom, and the first one is this: they have the fastest punch in the world. How fast, exactly? When asking about any animal’s fighting prowess, I find it helpful to ask the question, “Were it of proportionate size, would it win in a fight against Bruce Lee?” Well, Bruce Lee’s punches were so fast that the film had to be slowed down just so they were visible. The mantis shrimp’s punches are literally as fast as a .22 caliber bullet, and, like the pistol shrimp’s claw, creates a cavitation bubble that flashes white light as it collapses into a blisteringly hot shock wave. It carries 10,000 g’s of force. It completes the entire punch in under three thousandths of a second. And it does it in water.
Mama said knock you out
The mantis shrimp presents a dilemma for aquarists: how do you contain a creature that can and occasionally does punch through aquarium glass? How do you keep an animal that, if you count the boiling shock wave that accompanies the blow, literally has fists of fire?
Of course, not all mantis shrimps use their fists. Some use knives. The stomatopods are broken into two general categories: the spearers and the smashers. (And yes, these are the actual terms marine biologists use.) That peacock mantis shrimp above is a smasher: the club at the end of its spring loaded claw is used to punch through crab carapaces, oyster shells, and presumably bank vault doors. Spearers, like this squilla mantis, have razor-sharp spines for shanking fish in their guts. Either way, the effect is lethal and immediate.
Bruce Lee’s One Inch Punch:
Slowed down 10 times.
Mantis Shrimp’s One Inch Punch:
Slowed down 800 times.
But perhaps the most amazing thing about the mantis shrimp’s punch is that it’s not the most amazing thing about the mantis shrimp. For the mantis shrimp’s other claim to fame is that it has the best vision in the world. And by that, I don’t mean it doesn’t need glasses. I mean that it can see visual spectrums and types of light that no other animal we know of can see.
Humans have trichromatic “RGB” vision; we have three types of color-sensing cone cells in our eyes. The three lengths of cone cells are preferential for red, green, and blue wavelengths, making everything we see a combination or cancellation of those three colors. By contrast, the mantis shrimp has 16 types of pigment photoreceptors: 12 for color reception and 4 for color cancellation. So while we are really seeing the world in three primary colors, the mantis shrimps sees in twelve, the net effect being that the stomatopods can detect 100,000 different colors, ten times the number we can see. The world may seem colorful to our eyes, but the unfortunate fact is that the rainbow is holding out on us… there are thousands of variations of color that we can’t perceive, and the mantis shrimp enjoys them all.
And that’s just in our visual spectrum. The mantis shrimp can see into both the ultraviolet and the infrared as well. What’s more, the mantis shrimp’s ommatidia, or eye segments, are each divided into three specialized parts, allowing the eye to see the same object from three different angles. Our two eyes give us binocular vision; each eye of the mantis shrimp has trinocular vision for superior depth perception. What’s more, it can see linear polarized light, which is nearly invisible to us. What’s more, it can see circular polarized light, which is invisible to every other animal we know.
Mantis shrimp is looking at your brain waves.
Here’s where the physics come in: A primer on polarization. As you know, the funny thing about light is that it functions as both a particle and a wave. A friend standing across a room shooting spitballs at you — those spitballs being photons — would be a decent analogy for light, but so would a friend holding the other end of a jumprope. If the friend shakes the jumprope slowly, it appears red; a little faster, and it appears orange. If your friend shakes it very fast, putting a great deal of energy into it, the jumprope appears blue. By the time you can no longer see the jumprope, it’s become ultraviolet.
If the friend shakes his or her end of the jumprope up and down, that wave would be vertically polarized. If your friend shakes his or her end left and right, the incoming wave would be horizontally polarized. If you were wearing those stupid shutter shades that Kanye West has made so popular again, you’d only be able to fully perceive the horizontal polarization, the left-and-right movement of the jumprope; the shades would effectively filter any other direction of movement of the rope to your eyes. This is linear polarized vision, which many animals, including insects, birds, and octopuses, are known to have. The sun’s light isn’t polarized, but reflected sunlight can be; we perceive it as glare from water or snow. Animals perceive it as dazzling white-and-rainbow rays bouncing off objects, which is helpful in navigation, finding food, and attracting mates. The world is simply more resplendent when you can see polarized light.
I am drinking rainbows right now!
Now, imagine your friend with the jumprope starts swinging his or her end in a circle, making the rope’s waves come at you in a helix. This is circular polarized light, and no other animal but the mantis shrimp is known to be able to see it. In fact, not many things in nature can produce it. The shell of the scarab beetle seems lustrous enough to us, but to our eyes it’s comparatively dun; the structures that produce its color also send light reflecting back in a clockwise helix, which we’re not equipped to see. The glow worm also produces circularly polarized light (CPL), probably incidentally as it’s refracted through its skin. Another byproduct of refraction is the round manhole cover of visible light you see when you’re diving, known as Snell’s window; outside the window, in the dark parts, there is CPL. And, of course, when a mantis shrimp fluoresces during mating rituals, they’re producing it: a dazzling sexual display that’s invisible to every other animal.
Believe it or not, there is something invisible about this.
We know they use CPL vision for sexual selection. But is that the primary reason the mantis shrimp has evolved to see it? There are several theories. One is that many of the small animals a stomatopod may prey on are invisible, but the sugars they contain might reflect CPL, making them glow in the dark to the mantis shrimp’s eyes. Another theory holds that the complex eyes of the mantis shrimp are a substitute for a big brain. But stomatopods are among the more intelligent crustaceans, being able to recognize individuals of their own species and ours, and having something resembling a long-term memory. Whatever the reasons, we know that circular polarization of energy we only recently learned to harness for satellite communications and laser discs was originally invented 400 million years ago by the stomatopod. And we know that, in the mantis shrimp’s eyes, the world is unimaginably brilliant, full of hundreds of thousands of different colors, rich textures, pulsing auras and shining rays. Our eyes would not believe how beautiful the world truly is, which only the mantis shrimp can see. And when a mantis shrimp looks at you, he sees you as you truly are: radiant, gorgeously illustrated with colors for which we have no words, incandescent.
Then he tries to kick your ass.