Pistol Shrimp & Goby Mutualism

Brandon here. Some of my favorite saltwater organisms are the pistol shrimp. There are several hundred species of these shrimp found throughout the world. They are not only found in tropical reefs but closer to home. I have heard these little guys snapping away in muddy areas right offshore in Virginia. Despite the characteristic that gives these creatures their name, snapping shrimp are usually peaceful little critters and interesting additions to a reef tank.

Pistol shrimps belong to the family Alpheidae. They are characterized by their one large claw responsible for the snapping sound they produce. These shrimp are usually known for their mutualistic relationship with certain gobies. The shrimp will dig and tend to a burrow in a sandy or muddy substrate while the goby stands guard at the entrance, watching for prey and predators. The shrimp will even close the entrance to the burrow at night to keep predators out. There are also colonial species of shrimp that live in sponges, somewhat like ants in an anthill.

What makes pistol shrimp fascinating is their enlarged claw. The closing of the claw in itself does not produce the snapping sound. Rather there is a groove in the claw which channels water out as it closes. The water is forced out at around 60 miles per hour. This speed produces an area of low pressure and forms a bubble. When the bubble collapses, intense sound, heat, and even light are produced. This is where the snapping sound that we hear comes from. Temperatures of about 5000 degrees Kelvin, or about 8500 degrees Fahrenheit, can be reached. This blast of pressure is enough to kill small fish and invertebrates. The snapping shrimp is considered one of the loudest creatures in the ocean, and large colonies of them are loud enough to white out the sonar of submarines.

To give you a better idea of what this all looks like (or just to see a shrimp get blasted) watch this video:

Until next time,
Brandon