The newest additions to our tank are a Pistol Shrimp and a Watchman Goby. These two animals are usually purchased as a pair because they work and live together, and have a very unique relationship.
The Pistol Shrimp is blind, and needs the Goby to alert him if there is any danger nearby. The Watchman Goby is not a good burrower, so thus needs the shrimp to give him a home to stay in. Together, they live in the same burrow and are in constant communication with each other. The shrimp will often scavenge for bits of shell or rock to improve the burrow, and the Goby always accompanies him, keeping watch.
From our observations, the Goby is almost always at the mouth of the burrow watching, while the shrimp constantly bulldozes claw-fulls of sand out of their burrow and tunnels. If there is any apparent danger nearby, the Goby flicks his tail, alerting the shrimp to go back into the burrow. When the shrimp decided to go exploring, the Goby is right there with him, and the shrimp always has an antennae touching the Goby, so he always knows where he is. If they are several inches from their home and they get spooked, the speed in which they can move back to home base is astonishing.
The shrimp has two claws; one is small, and the other much larger. The larger claw has the ability to snap at a speed so fast it creates what is known as a cavitation bubble. This bubble causes acoustic pressure, which creates a snapping sound clearly audible outside of the aquarium, and can kill small fish. I have read that the bubble can reach 60 miles per hour and over 200 decibels. We had some reservation at first of adding this pair to our tank, hearing some rumours about the cavitation bubble causing aquariums to crack. Our LFS assures us that that is not the case.
In the wild, the shrimp snaps as a way to communicate, as well as to hunt. We do hear this snap noise sometimes, but I doubt it is a result of any hunting; our shrimp and Goby eat pellets as well as mysis shrimp every day. They stay to themselves and are not very social, so I think this snapping is more a way to communicate to each other.
Below you can watch the way the Goby communicates with the shrimp, and how the shrimp’s antennae is always touching the Goby.