Natures wonders: a tiny shrimp's powerful claw (Introduction)

by David Turell @, Friday, October 27, 2017, 23:45 (662 days ago) @ David Turell

A five centimeter shrimp can hurt your hand.Don't go in the water:

https://www.newscientist.com/article/2151700-how-a-tiny-shrimp-fires-a-savage-shock-wav...

"This reef ain’t big enough for the both of us. Two pistol shrimp face each other, each spreading open its giant snapping claw – nearly half the size of its body. One or both of them then snaps the claw shut in its opponent’s direction, firing off a powerful water jet at speeds up to 30 metres per second.

"These shrimp shootouts are rarely fatal, but can leave the loser retreating with missing claws or puncture wounds. But the high-speed squirt isn’t what harms their target – it’s the resulting shock wave. Now we have glimpsed how this unfolds in fine detail.

***

"They found that when the claw snaps shut, friction between the fast-moving jet and the still water surrounding it creates a swirling vortex. Once the vortex starts spinning rapidly enough, it leaves a void in the center, like the dimple in your tea as you stir it.
Eventually that void collapses, and as it does, it releases a powerful pressure wave. All of this happens in less than half a millisecond, Koukouvinis says.

"Because these shrimp only grow to about 5 centimetres, their underwater weapons are limited to targeting animals of a similarly minuscule size. But Nancy Knowlton at the Smithsonian Institution in Washington DC doesn’t recommend sticking your hand in any tank holding the shrimp.

“'You wouldn’t feel anything if you’re just snorkelling near a reef, but if you have your hand in front of a shrimp’s claw you’re definitely feeling it when it goes off,” she says. “It hurts.”

"And that’s the point. Pistol shrimp are scavengers, eating detritus on the sandy ocean floor, so they don’t often use their bubble-gun claws to stun prey, Knowlton says. Instead, they use their shock waves to protect their mates and homes in some of the tiniest gunfights on earth."

Comment: Like the bacterial spear, small organisms can develop amazing weapons.


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