What You Need to Know about Pistol Shrimps
Pistol Shrimps are shrimps that comprise over 1000 species across 38 genera. Together they form the Alpheidae family. Snapping shrimp get their nickname from their signature large snapper, which allows them to hunt and communicate among the world’s coral reefs. The snapping is a major source of noise in the ocean, and has disturbed human activity.
1. A Pistol Shrimp’s Snapper Can be Over Half the Size of its Body
Snapping Shrimps have one small claw called a pincer, and a much larger claw-like snapper. Some shrimps have snappers that are bigger than half its body. The agility of a snapping shrimp is a testament to its strength for its size. The snapper is the shrimp’s weapon for killing or stunning prey. However, they don’t grab or choke prey the way a crab does. Instead, the snapper has a complex mechanism that gives it much more power.
2. The Snapper Has Two Halves that Turn Water into Bullets
The snapper of each Bullet Shrimp has two halves. The first half is the propus, which has a socket and does not move. The other half is called the dactyl, which moves and has a plunger that fits snugly into the socket. The shrimp opens the dactyl using special muscles, letting water enter the socket. When the dactyl slams its plunger into the socket, it releases a jet of water bubbles at 25 miles per second.
3. The Pistol Shrimp’s Snapper is Regenerative
Snapping Shrimps can grow new snappers. Shrimps will shed their snapper during molting, or to make a desperate escape from a predator. When the shrimp loses its snapper, a pincer grows in its place. The pincer that the shrimp already had will molt into a new snapper. So the pistol shrimp can be considered ambidextrous. In rare cases, pistol shrimps have grown two snappers.
4. Pistol Shrimps Snap at 97km/hr
Since Pistol Shrimps are so small, they have to be fast to survive in the wild. Tiger Pistol Shrimps snap at 97 km/hr (60m/hr). The snap is too fast for humans to see without a slow-motion camera. Scientists had to use an ultra-high definition camera that took 40,000 frames per second in order to see that the propus and dactyl do not make full contact.
5. Bullet Shrimps are Louder than a Gunshot
The snap reaches 210 decibels. An actual gunshot usually only reaches between 165-175 decibels. Pistol Shrimps rank among Sperm Whales and Baleen Whales for the loudest creatures in the ocean. Sperm Whale clicks reach around 230 decibels, while the calls of Baleen Whales reach around 188 decibels. Shrimps live in large colonies, so the snapping of hundreds of shrimps create significant noise in the ocean.
6. The Snapping is Loud Enough to Interfere with Sonar Radio
Military Officers are very familiar with the constant popping of snapping shrimps. The sound of hundreds of shrimps snapping at once creates enough noise to disrupt underwater Sonar activity. During World War II, the popping disrupted Japanese sonar radios enough for allied ships and submarines to sneak into Japanese territory undetected. In recent years, snapping shrimp have disrupted underwater drone operations in Singaporean waters.
7. Cavitation Bubbles, Not the Snapper, Make the Deafening Pop
The shrimp’s signature snapping sound doesn’t come from the force of the snapper closing. It comes from the jet of water pushed out. Pistol Shrimps create cavitation when they snap. The pressure of the water bubbles released is lower than the normal vapor pressure of water. This causes the bubbles of water already there to swell and burst. When the bubbles burst, they make the snapping sound.
8. When Cavitation Bubbles Burst, they reach 4000℃
When Pistol Shrimps snap, the jet of water released creates little areas with a vapor pressure lower than the vapor pressure of water. Little bubbles of air already present in the water expand rapidly. When the bubbles return to regular water pressure, they implode. The energy released is so intense that a bubble can heat up to 4000℃. This is four times hotter than Lava (1000℃) and almost as hot as the surface of the sun (5500℃).
9. Pistol Shrimps Produce a Sonic Boom Powerful enough to Break Glass
The low frequency of a pistol shrimp’s sonic boom ranges between 2000hz and 5000hz. For reference, a sonic boom that’s only 550hz will shatter glass. Tiger pistol shrimp are popular pets because of their mild temperament. However, keeping a pistol shrimp in an aquarium is risky, because the snap could shatter the glass.
10. Pistol Shrimps Create Light When they Snap
When a low pressure bubble implodes, it briefly emits a flash of light. This effect is called sonoluminescence, and happens in bubbles with a high energy concentration. Scientists first discovered wildlife producing this effect when they observed Pistol Shrimps snapping. The flash only lasts for 300 microseconds. Additionally, the intensity of the light is below the average light intensity from sonoluminescence. Thus, the flash isn’t visible to the naked eye.
11. Some Pistol Shrimps Live in Colonies of Three Hundred or more, like Bees
Bullet Shrimps are very social creatures. They typically live in colonies of three hundred or more. The colonies of the species Synalpheus regalia are eusocial, like bee colonies. Each regalia colony is centered around a queen. The queen is the only shrimp who reproduces. All the other shrimps are responsible for raising the young and protecting the colony. Snapping Shrimps are the only known marine life to live in this type of structure.
12. Most Snapping Shrimp are Monogamous
Most Snapping Shrimp species are monogamous. Females become receptive to male mates just after molting. Mating is only possible for a few hours after the female molts. The male shrimp will mate and then protect the female. The shrimps can mate more than once throughout their lifetime, so the couples stay together for life. Studies have shown that males with larger snappers have better success in attracting females.
13. Pistol Shrimps also Use the Snapper to Communicate
Pistol Shrimps don’t just snap to hunt, they also snap to communicate. Within their reef colonies, the shrimps like to make their own dens. Pistol shrimps “talk” to each other from their burrows by snapping. The rapid movement means that a shrimp who senses food or predators can instantly alert other shrimps in the colony instantly.
14. Pistol Shrimp and Goby Form Alliances
Pistol Shrimp and goby form symbiotic relationships. While the snapping shrimp blasts into the coral to make a home or look for food, the goby will stay outside and look out for predators.
The shrimp’s antenna will keep contact with the goby’s tail. If the goby senses danger, it can flick its tail against the shrimp’s antenna as a warning. The shrimp uses its snapper to deter predators, but might knock the goby unconscious on accident.
Is There a Consensus to What Snapping Shrimp Sound Like?
Some people think the snapping of Pistol Shrimps sounds like bacon frying. Others think it sounds like Popcorn in the microwave. Some even say the static of a broken TV. Comment below what you think the snapping sounds like.
How endangered is this animal?
- Pistol Shrimp Snapping is a Sign of a Healthy Coral Reef.
Experienced divers are used to the cacophony around coral reefs. Even though military officers consider the noise an obstacle, marine biologists embrace it. Scientists listen for snapping to determine the health of a coral reef. Rising ocean temperatures present a growing threat to coral ecosystems. But the sound of snapping shrimps offers hope. A noisy reef is a healthy reef, because it can support hundreds of snapping shrimps.
- Global Warming Threatens the Health of Coral Reefs Worldwide.
Scientists believe that a global temperature increase of 2℃ will kill 99% of the world’s coral reefs. Pistol shrimps, like millions of other species, need healthy reefs for food and shelter. Without these reefs, pistol shrimps will suffer.
- Warmer Oceans will Make Pistol Shrimps Even Louder.
Scientists studying Pistol Shrimps both in the ocean and in labs found that the shrimps are more active in warm water. Pistol Shrimps are already a major source of ocean noise. As ocean temperatures rise, scientists are concerned that the even louder snapping will affect other species. Louder snapping can increase stress in marine life, or inhibit fish from communicating.
Also Known As
Bullet Shrimp, Snapping Shrimp
3-5cm (1.2-2.0in) long
Tropical Western Pacific and Indian Oceans
Coral Rocky Bottoms, Coral Reefs
Small Fish, Prawns, Krill
4 years in the wild, 2-3 years as pets