Sunday, July 3, 2011

Mantis Shrimp

Mantis shrimp.
Ah... In cantonese we call it 攋尿蝦(pissing shrimp). Why pissing? Because they tend to shoot a jet of water when picked up.
Anyway, this seemingly harmless crustacean is actually one of the wonders of nature. Mantis shrimp is neither mantis nor shrimp, and the name was given simply because of their resemblance to praying mantis and shrimp.
There are around 400 species of mantis shrimp worldwide, and they are categorized based on the types of claw they possess.
So what's so special about this shrimp? Er...sorry, crustacean.
I watched Animal Planet several years back and there was this documentary listing the top ten loudest animals of the animal kingdom. And surprisingly this little crustacean topped the chart. Why loudest?

To understand that we must first understand the source of the sound, the claws. The claws of mantis shrimp are really special, and they use it to smash the life out of their prey, literally. They strike their prey by rapidly unfolding and swinging their raptorial claws at the prey, and are capable of inflicting serious damage on victims significantly greater in size than themselves.
And I'm talking about really severe damage. The claws of a mantis shrimp travels with an acceleration of 10,400 g (102,000 m/s2) and speeds of 23 m/s from a standing start, about the acceleration of a .22 calibre bullet. The velocity of the strike generates an instantaneous force of 1,500 newton, and at the same time generating cavitation bubbles between the appendage and the striking surface. The collapse of these cavitation bubbles produces shock wave that is enough to kill or stun the prey.
And this shock wave is the reason why they are so loud-it's a sound wave that is strong enough to kill its prey. Larger species of mantis shrimp, in rare cases, could break aquarium glass with their strikes. Amazing huh~?

Apart from its powerful claw, the mantis shrimp also possesses the most advanced eye of any animals on Earth. Its compound eyes sit on independently moving stalks, and they can see in twelve colours (humans see in only three). Humans can't distinguish between polarized and nonpolarized light, whereas the eyes of a mantis shrimp can detect circular polarized light which can’t be detected by any other creature.
We do have this application, in the form of DVD and CD players, where a device called quarter-wave plate converts polarized light signals inside DVD and CD players. Quarter-wave plates are also used inside satellite transmitters and other high-tech communication systems, which rely on the data-dense, loss-free transmission properties of circular polarized light.

But even our best quarter-wave plates can only detect circular polarized light in a few colors. The quarter-wave plates of mantis shrimps work across the visual spectrum, for any color of CPL.


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