Photo of the Week: April 26, 2010

Hi Gang!

This week’s POTW is an image of a pair of shrimpgobies standing watch over their burrow as snapping shrimps works outside of their shared home. The image is from the Indonesian island of Bali.

At least 70 species of gobies described in eight genera are commonly known as shrimpgobies (aka shrimp gobies and watchman gobies). These gobies form mutually beneficial symbiotic relationships with a variety of snapping (aka pistol) shrimps described in the genus Aplheus. These seemingly unlikely partners live together in a shared burrow. The nearly blind shrimps spend their days digging and maintaining the burrows, and they would be easy winners in any kind of underwater good housekeeping contest as they do superb jobs of keeping the burrow neat and orderly.

The sandy or muddy burrows tend to collapse fairly frequently. The shrimps are excellent excavators, and these earth-moving invertebrates spend extraordinary amounts of time clearing out a collapsed burrow and, in some instances, reinforcing the burrow walls.

The shrimpgobies are incapable of digging a burrow, but do serve as excellent look-outs. The shrimps depend on their ever-watchful partners to keep an eye out for potential danger. When working outside of the burrow, the shrimps keep at least one antenna in contact with a shrimp goby. If the goby detects a threat it will quickly retreat into the burrow, and the shrimp will instantly get the message to “retreat now” as contact between shrimp and shrimp goby is broken. In essence, the gobies serve as early warning detection systems for the sight-challenged shrimps.

The shrimp gobies rarely display any aggression toward other fishes their own size, the exception being that they do show aggression toward other members of their own species unless the two fish in question are a mated pair.

The shrimps and their partner gobies work and patrol the area outside of their home burrows during the day. Studies have indicated that the shrimps spend more time building and maintaining burrows during morning hours, and spend their afternoons foraging for food and taking care of their own grooming needs. Both the shrimps and the shrimpgobies retreat into the safety of the burrow around sunset, and they will remain there throughout the night.

It is obvious to ichthyologists that there is a strong attraction between the shrimp gobies and their partner shrimps, but it is not exactly clear how the fishes and shrimps find each other in the wild. It is believed that the shrimpgobies primarily rely on vision to find the shrimps, while the shrimps depend mostly upon chemical cues to find the shrimpgobies.

I do hope you enjoy this week’s POTW and the natural history information that accompanies the photograph.

See you next week!

Marty