Super Family: Alpheoidea
The pistol shrimp competes with much larger animals like the Sperm Whale and Beluga Whale for the title of ‘loudest animal in the sea’. Amazing, given that the pistol shrimp is only 1–2 inches (3–5 cm) long.
It is distinctive for its disproportionately large claw, (larger than half the shrimp’s body) which does not have pincers at the end. Rather, it has a pistol-like feature made of two parts. A joint allows the “hammer” part to move backward into a cocking position like a gun. When released, it snaps into the other part of the claw, creating a cavitation bubble capable of stunning fish and breaking small glass jars.
As the bubble extends out from the claw, it reaches speeds up to 60 miles per hour (97 km/h) and releases a sound reaching 218 decibels. The duration of the click is less than 1 millisecond.
The snap can also produce sonoluminescence [light] from the collapsing bubble. As it collapses, the cavitation bubble reaches temperatures of over 5,000 K (4,700 °C). In comparison, the surface temperature of the sun is estimated to be around 5,800 K (5,500 °C). The light is not visible to the naked eye. It is likely a by-product of the shock wave. It was the first known instance of an animal producing light by this effect.
The snapping is used for hunting, as well as for communication. When feeding, the shrimp usually lies in an obscured spot, such as a burrow. The shrimp then extends its antennae outwards to determine if any fish are passing by. Once it feels movement, the shrimp inches out of its hiding place, pulls back its claw, and releases a “shot” which stuns the prey; the shrimp pulls it into the burrow and feeds. Source
Excellent video of the Pistol Shrimp in action:
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The science behind pistol shrimp is really cool. The speed at which their claw can move and the resulting bubble’s effect are incredible. We should all be thankful that such a small animal has this capacity, imagine if even the claws of your average coconut crab had that kind of power (not that they aren’t fierce themselves already!)