How can a little thing like this, create such an incredible amount of energy?
In: Biology
The shell of their pistol claw is flexible and acts like a spring, along with springy tendons. The pistol shrimp opens its claw against the spring action of the claw shell and tendons, which stores the energy as tension. When the shrimp releases its claw, it pulls it shut with muscles *and* the stored tension in the spring, slamming it closed with great force.
One half of the claw has a groove in it, and the other has a slot that fits into that groove. The groove is full of water until the claw closes and the slot shoves the water out of the way with all of that force. The groove has a narrow outlet that limits how much water can leave. A quirk of fluid dynamics is that when you narrow the flow without decreasing the force behind it the fluid has to accelerate. This means that as the water is forced out of the groove it rapidly accelerates until it’s going faster than the speed of sound in water.
This creates a shockwave not unlike a [mach cone](https://upload.wikimedia.org/wikipedia/commons/e/e1/FA-18_going_transonic.JPG), except water can’t flow fast enough to fill the space caused by the shockwave. This creates the cavitation bubble – a bubble of vacuum that rapidly collapses. As the sides of the bubble slam into each other, it creates *another* shockwave that is the loud pop of the pistol shrimp.
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