Young snapping shrimps’ tiny claws can accelerate in water like a bullet, new research suggests.
The adult animals, Alpheus heterochaelis, use the technique to stun passing fish and foes with a simple click of a spring-loaded claw.
This squirts a high-speed jet that rips through the water and creates a vapour-filled bubble (a cavitation bubble), invisible to the naked eye, that then implodes.
The action creates a catastrophic shock wave – complete with a sharp popping sound and minute flash of light – to incapacitate their opponent.
Jacob Harrison, from the Georgia Institute of Technology in the US, said: “We can’t see the bubble with our naked eyes, it happens too fast, but we can hear when the bubble collapses.”
Found in the western Atlantic Ocean and the Gulf of Mexico, the adult shrimp’s claws crash together at eye-watering speeds of up to 30 metres per second and the whole process is over in less than a millisecond.
Researchers looked at what stage in life this trigger claw developed.
While a graduate student in Sheila Patek’s Duke University laboratory, Mr Harrison became a surrogate parent to a group of developing snapping shrimp.
He discovered that the youngsters are capable of accelerating their upper claws in water as fast as a bullet from a gun and 20 times faster than their parents.
Having collected four snapping shrimp females carrying eggs from the mudflats off Beaufort, North Carolina, Mr Harrison nurtured the shrimp youngsters after hatching, keeping track of their growth, until they began snapping their claws at around the age of one month.
The researcher aggravated the shrimps with toothpicks so they would snap, and after filming more than 280 claw snaps, he reconstructed 125 of the manoeuvres.
He calculated the acceleration of the claws as they crashed shut, the amount of energy used and the power required to produce the water jet.
The study found that even the tiniest snapping shrimp – with 1mm long claws and weighing just 0.03mg – could occasionally squirt a jet of water producing an explosive cavitation bubble.
Mr Harrison said: “I was completely ecstatic. This snapping shrimp was about the length of a staple and it could move fast enough to cavitate water.”
He was astonished to discover the acceleration of the snap was as fast as a bullet and around 20 times faster than the adult’s claw.
However, he suggests the youngsters have to fire a few blanks before they build up to producing cavitation bubbles.
The discovery that snapping shrimp youngster’s claws are the fastest accelerating reusable body part in water is published in the Journal of Experimental Biology.