Monday, August 22, 2005

Nature is always stranger than you think:
The snapping shrimp (Alpheus heterochaelis) produces a loud snapping sound by an extremely rapid closure of its snapper claw. It was commonly believed that the sound is generated when the two claw surfaces hit each other. We show that the sound, in fact, originates from the collapse of a cavitation bubble. During the rapid snapper claw closure a high-velocity water jet is emitted from the claw with a speed exceeding cavitation conditions. Hydrophone measurements in conjunction with time-controlled high-speed imaging of claw closure demonstrate that the sound is emitted at the cavitation bubble collapse. A model for the bubble dynamics based on a Rayleigh-Plesset type equation quantitatively accounts for the time dependence of the bubble radius and for the emitted sound.

We now also report that a short, intense flash of light is emitted as the bubble collapses, indicating that extreme pressures and temperatures of at least 5,000 K must exist inside the bubble at the point of collapse. We have dubbed this phenomenon 'shrimpoluminescence' — the first observation, to our knowledge, of this mode of light production in any animal — because of its apparent similarity to sonoluminescence, the light emission from a bubble periodically driven by ultrasound.
"Shrimpoluminescence"?