Dr. Patek and fellow researchers have clocked the shrimp's punt at more than 45 miles an hour – underwater. That makes it the new world champ for so-called feeding strikes – the movement animals make to nail their prey. It's nearly twice as fast as a punch a boxer typically throws in open air and delivers a force of more than 200 pounds, with the club accelerating with a force of some 10,000 Gs – 500 times more acceleration force than humans can endure.
And that isn't all. Patek's team also found that the strike imparted a second rattling impulse to a creature's shell that came quickly on the heels of the first strike. When the researchers examined high-speed video, they saw a brief flash of light at the point of contact – the telltale signs of cavitation.
Cavitation is a destructive process marine engineers know well. In this case, the club is moving so fast that it creates an area of intense low pressure between the club tip and the object it's striking. The water there literally vaporizes, forming a bubble that quickly collapses, generating sound, light, heat, and its own impact with a force comparable to the impact from the shrimp's club.
When Dr. Kisailus was hunting for natural materials that could help humans engineer better materials, he and colleague James Weaver, now with Harvard University's Wyss Institute for Biologically Inspired Engineering, came across the research.
"We're, like, wow!" recalls Dr. Kisailus.
So the team went to work analyzing the club's structure and composition. The results appear in the June 8 issue of the journal Science.
One surprising discovery was that the club is not one uniform unit but is composed of three regions, Kisailus says.