The reef is full of interesting creatures and fascinating adaptations and survival techniques used by reef inhabitants to prevent becoming food to predatory fish. Often this survival evolution results in some interesting partnerships between marine creatures. One of the more curious relationships that most divers would have come across, is that between the marine goby fish and the shrimp.
The Pistol Shrimp or Snapping Shrimps of the Alpheus shrimp, family are great diggers, and constantly create and maintain burrows in the sea beds sand using its large claws. However the shrimp have really poor eye-sight and being almost blind, cannot spot their predators until it’s too late. The Goby fish (Gobies in the genus Amblyeleotris, Cryptocentrus, Ctenogobiops, Istigobius, and Stonogobiops) on the other hand are small vigilant fish that form a symbiotic relationship with the shrimp and act as the shrimp’s watchman against predators, in exchange for shelter in the shrimp’s burrow.
The goby will usually sit at the entrance of the burrow maintaining a constant vigil against potential predators, while the shrimp bulldozes away clearing gravel from the burrow. Whenever the shrimp needs to dump gravel outside the burrow, it is usually exposed to potential predators. However with the Goby keeping lookout, the shrimp places one tentacle on the Goby while exposed, so if the Goby darts inside the burrow, the Shrimp instantly is alerted of the presence of a predator and it too darts back inside the safety of its burrow. The partnering between these two creatures is only that of a watchman and housekeeper. Gobies eat micro-fauna and sometimes tiny fish they find near the bottom, the shrimps feed on what they find in their burrowing and hence do not compete for food.
So how do the Gobies and Shrimp find each other in the first place? Shrimp-goby researchers have been trying to figure out this one for a long time, and have conducted numerous experiments to determine whether the Gobies find the shrimp, or vice versa, and also to determine whether they locate each other optically or are attracted chemically. There has been no definitive answer as to who spots who in this symbiotic relationship and it is still one of nature’s mysteries.
So the next time you spot a goby while scuba diving, perched vigilantly near a burrow, look closely and you will more often than not, spot the housekeeper shrimp hard at work bulldozing clawful after clawful of sand. Spend some time watching this interesting relationship and I can tell you , you will not be disappointed.