Photo: Dan Schofield · CC BY 4.0
Snap
A pistol shrimp's snap creates a bubble that briefly gets about as hot as the surface of the Sun.
4 min readLast updated
The short answer
Yes, briefly. Pistol shrimp snap their claws so fast they form a cavitation bubble. As it collapses, temperatures inside are estimated to reach several thousand degrees Celsius, around that of the Sun's surface, for a tiny instant.
Why it's true
Pistol shrimp have one oversized claw. When it snaps shut, it shoots out a jet of water so fast that pressure drops and a bubble forms. This is called cavitation. The bubble then collapses violently, producing a loud crack, a shockwave and a tiny flash of light.
In 2001, researchers in the Netherlands recorded this flash, called shrimpoluminescence. Based on the light, they estimated temperatures inside the collapsing bubble of at least 5,000 kelvin, roughly 4,700 degrees Celsius, close to the Sun's surface temperature. The heat lasts only a tiny fraction of a second and affects a very small space, so it does not boil the water around it.
The sound comes from the bubble collapse, not from the claws striking together.
By the numbers
~4,700 °C
Estimated bubble temperature
2000
Cavitation discovery published
2001
Flash of light reported
Hundreds
Known pistol shrimp species
How we know
Scientists long assumed the snap came from claw parts hitting each other. In 2000, Michel Versluis and colleagues used high speed cameras and hydrophones to show the noise came from a collapsing cavitation bubble. The work was published in Science and transformed understanding of the shrimp.
A year later, the team published results in Nature showing the faint flash of light from the collapsing bubble. Pistol shrimp colonies are so loud that during World War II, their crackling noise interfered with submarine sonar, and navies used the noise to help hide submarines near reefs.
Light from sound
The flash from collapsing bubbles is similar to sonoluminescence, where sound waves in a lab create bubbles that emit light.
Pistol shrimp produce it naturally, making them a living example of this puzzling physics.
Worth remembering
- Pistol shrimp snap claws so fast they form a bubble.
- The collapsing bubble briefly reaches Sun like temperatures.
- The snap's sound comes from the bubble, not the claws.
In context
Cavitation is familiar to engineers. It can damage ship propellers and pumps, eating away metal surfaces as bubbles collapse repeatedly. The pistol shrimp has turned the same physics into a weapon.
Mantis shrimp also create cavitation bubbles when they strike. These bubbles add extra force to each blow, helping them smash shells.
Pistol shrimp sometimes live in partnerships with gobies. The nearly blind shrimp digs a burrow, while the goby keeps watch and warns of danger with tail flicks.
A closer look
Reef noise
Healthy coral reefs crackle with the sound of snapping shrimp.
Scientists use this noise to monitor reef health, and young fish may use reef sounds to find homes.
Claw swap
If a pistol shrimp loses its big claw, its smaller claw can grow into a new snapping claw.
The lost claw's side then regrows as the small claw, reversing the shrimp's handedness.
Living in sponges
Some pistol shrimp live in sponges in colonies with a queen, similar to bees or ants.
These are among the few known social marine animals.
Related facts
Another remarkable crustacean mantis shrimp have 12 colour receptors.
More reef surprises clownfish can change sex.
For where pistol shrimp live coral polyps are animals.
Why reef noise carries so far sound travels faster in water.
Key terms
- Cavitation
- The formation and collapse of bubbles in a liquid due to pressure changes.
- Shrimpoluminescence
- The flash of light from a pistol shrimp's collapsing bubble.
- Hydrophone
- A microphone designed to record sound underwater.
Myth vs reality
Myth
The shrimp's snap sound comes from its claw parts clacking together.
Reality
The sound comes from a collapsing bubble created by the snap.
People also ask
How hot is a pistol shrimp's snap?
The collapsing bubble is estimated to reach at least about 4,700 degrees Celsius for an instant, similar to the Sun's surface.
Does the snap boil the water?
No. The heat lasts only a tiny fraction of a second inside a very small bubble.
Why do pistol shrimp snap?
To stun or kill small prey, to defend territory and to communicate with other shrimp.
How loud is a pistol shrimp?
Colonies create a constant crackling sound underwater that can interfere with sonar and is a major part of reef noise.
What is cavitation?
The formation of bubbles when water pressure drops sharply, followed by their violent collapse.
