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Message:

> 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-wave-using-just-its-claw/
> 
> "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.