Tuesday, March 6, 2012

I can shoot a pistol, and so can a SHRIMP?!

Alpheus digitalus (Pistol Shrimp)

The common name of this brightly colored shrimp is Pistol shrimp and its scientific name is Alpheus digitalus.  The pistol shrimp is apart of the phylum Arthropoda and the order Decapoda.  These little pistol shrimp belong to the family, Alpheidae, which contains over 600 species.  Most snapping shrimp dig burrows and common inhabitants of coral reefs, submerged seagrass flats, and oyster reefs.  

Explanation of the shrimp and how it shoots!

The pistol shrimp grows to be 1 to 2 inches long, so they are experts at hiding due to their small size.  They are distinctive from the other shrimp (species) due to their large claw that is larger than half of the shrimp's body.  The shrimp's claw can be found on either arm and does not have pincers at the end.  Instead of pincers like several other individuals, the shrimp's claw is composed of a pistol-like feature made to two separate parts.  A joint in the claw allows the "hammer" to shift backward and create a right angle position.  When the muscle in the claw releases the hammer, it snaps against the other part emitting a wave of bubbles that is capable of stunning larger organisms (fish) and even break small glass jars due to the enormous amount of power the snap creates.

These little fighters can stun much larger prey than themselves, who would think they could possibly have friends?  Well, they do.  Good thing for the goby fish, they are not preyed upon by the pistol shrimp, but live in a symbiotic relationship together.

Goby Fish (goby fishes)
The small little shrimp digs its way through the sand to build a burrow.  The burrow is tended by the pistol shrimp and the goby provides protection to the burrow by watching out for danger.  If both the shrimp and fish are away from the burrow the shrimp maintains contact with the goby by using it antenna.  The goby has better vision in the relationship, might as well be a marriage, so the goby uses its vision to watch for danger and if there is any it alerts the shrimp of danger using a characteristic tail movement.  They both retreat together into safety of their shared burrow.  This has been studied and observed in coral reef habitats.

This is filmed in a tank, but still displays their symbiotic relationship

The pistol shrimp snaps its specialized claw shut to create a Cavitation bubble that generates great pressure for such a little individual.  The bubbles can reach speeds up to 60 mph and the claw releases a sound of 218 decibels.  The collapsing bubbles can produce sonoluminescence (emission of short bursts of light form imploding bubbles in a liquid when excited by sound).  As the bubble collapses it reaches temperature of over 4,700 DEGREES CELSIUS!  That is just a little bit shy of the suns temperature (5,500 degrees Celsius).  This light created in the water cannot be seen by the naked eye.  This is the first known instance of an animal producing light by this effect.

The pistol shrimp uses this adaption for both communication and hunting.  When feeding the shrimp hides (burrow) and sticks out it antennae to determine movement.  When it does it slowly inches outward, pulls back its claw, and FIRES, releasing a shot of hot, pressure filled bubbles to stun the prey.  The shrimp then pulls it into the burrow to feed.

And I thought only humans can shoot, guess I was WRONG!



  1. This is a really interesting post. I never knew or heard anything about this shrimp before this post. The relationship between the Goby and the shrimp is neat, too. And that bubble reaching 4700 degrees Celsius is ridiculous... no wonder that little guy died in the video!

  2. I saw some of these symbiotic goby/shrimp pairs when diving on the great barrier reef. I had read about them, but it was great to see them in person.