Watch out for this little guy!

Do you like shrimp for dinner? Well don’t mess with this pistol packing hombre! Despite being a diminutive 1–2 inches (3–5 cm) long, the pistol shrimp normally has one regular claw but also has an oversized claw which operates as an acoustic weapon capable of producing ‘gunshots’ reaching over 200 decibels (much louder than a jet engine!).

Unwary victims approaching within an inch or so (~4 cm) of this oceanic ‘bush-whacker’ may find themselves staring down the barrel of a gun that is literally cocked and triggered in a fashion reminiscent of a Wild West six-shooter.

Reach for the sky!

The sound the shrimp makes is not produced by its claws snapping together but by a bubble formed by a fast water jet (travelling at speeds of up to 60 miles/100 kilometres an hour) squeezed out from a socket in the claw when it snaps shut (this generates a low-pressure bubble).

The violent implosion of this cavitation bubble produces the sound blast, the pressure of which is strong enough to kill small fish. (This is similar to the pistol shrimp’s larger cousin, the 4–6 inch-long (6–10 cm) mantis shrimp’s use of cavitation to boost its ‘super powered’ punches). Researchers using high-speed cameras and sound equipment say this whole process occurs within 300 microseconds from when the shrimp ‘pulls the trigger’. The implosion also briefly generates a temperature as high as the sun’s surface.

The shallow ocean gang

Not only are these shrimp armed and dangerous, they are also a rowdy bunch (“ … the shrimps’ snapping is the dominant source of background noise in the shallow ocean”1). They can easily compete with 40 ton heavyweights like whales in terms of ability to create noise….

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