Shrimpoluminescence

 In the year 2000, scientists from the Technical University of Munich along with scientists from the University of Twente (it's in the Netherlands) discovered something fascinating while researching Pistol Shrimp.  They were examining how such a tiny animal (they're in the range of 2cm long) could make such a loud noise.  How loud?  Well, they're in the running for the loudest animal on the planet.  How loud is that?  Well, here's a handy diagram that shows various levels of volume in decibels:

It should be pointed out that instant perforation of the eardrum is generally estimated at 160dB.  Alright, so where does our little Pistol Shrimp show up in that diagram?  Well, he doesn't.  He's off that scale.  And off every other scale I could find in graphic form.  You see, there's a theoretical limit on how loud things can get in air; any louder and you technically stop getting sound and you start getting shockwaves.  That's somewhere in the neighbourhood of 194dB.

But the limit is different in water.  It is much, much higher.  Our wee little shrimpy friend creates sounds as high as 218dB.  That's loud enough to kill other animals, and has even been known to break glass jars that people are holding the shrimp in.  They do it by clicking one of their claws shut extremely quickly, which creates a cavitation bubble (think the trail of bubbles that a spinning propeller creates).  The collapse of this bubble makes a loud popping sound.  Sound is nothing but pressure waves, and so the sound of this popping bubble literally does concussive damage to the animal the shrimp aims it at (think flash-bang grenades).

Alright, very cool, but what the hell is Shrimpoluminescence you ask?  Well, it turns out that the collapse of this cavitation bubble produces not just sound, but light and heat as well.  A lot of heat.  Almost as hot as the surface of the Sun hot.  It's only a very small amount that quickly dissipates into the surrounding water, but at the center of it, in a very tiny area, the temperature is over 4,700°C.  There's not much light though, it's not visible to the naked eye, but it does exist.  It's technically called sonoluminescence (light formed by imploding bubbles that are formed by sound), but honestly, isn't Shrimpoluminescence much more interesting?



That clicking sound you hear? That's the sound of evolution being awesome.

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Sources
Decibel level image
Wikipedia article on sound pressure (dB)
University of Twente - official, outdated website for the researchers who discovered shrimpoluninescence
Fun article on pistol shrimp
Daily Mail article on pistol shrimp
Wikipedia article on sonoluminescence