The Blue Speckled Shrimp Goby (Cryptocentrus caeruleomaculatus) is a common inhabitant of the silty shallow areas of the Tanzanian coasts. They are also known as the Eight-barred Shrimp-goby. As their name implies they have a symbiotic relationship with species of alpheid shrimp.
The shrimp constructs a burrow in the sand and both parties live in the burrow. The goby acts as a guard for the shrimp which has poor eye sight. Both species gain protection and more from this relationship making it a true symbiotic relationship.
The Blue Speckled Shrimp Goby has a proportionally elongated body and large eyes on the top of their head giving them a good field of vision. The base body colour is a light yellow greenish colour and there are eight darker reddish colored bars on the body. These bars seem more prominent on the smaller specimens. As their name suggests the body is covered in light blue spots. On some specimens there are red dots as well. The pelvic fins are well developed and the fish use these to perch on. They grow up to 9 cm in length.
BLUE SPECKLED SHRIMP GOBY IN THE WILD
The best way to observe these fascinating fish in the wild is on a low tide in the shallows when one can use a snorkel to breathe. With a scuba tank when one breathes out even if very carefully, the bubbles usually frighten the fish and they dart back down the burrows. If one approaches the burrows very carefully with a camera with video lights on it the fish seem to ignore one.
Once in position if one sits very still the fish will even leave the burrow to go off and feed. If one is lucky the shrimp acting like a bulldozer will clean the burrow out while one is watching. In some burrows there are pairs of shrimp and fishes and in others there is a single shrimp and fish.
The fish and the shrimp remain in physical contact with each other for most of the time, with the gobies tail almost constantly in touch with the shrimp. If one moves while the shrimp is out the burrow the gobies gives its tail a fast flick and both shoot down the burrow at quite some speed. If one waits the goby will eventually stick its head out the burrow and when it feels safe will partially emerge again.
OTHER INTERESTING FACTS AND OBSERVATIONS
At times both the shrimp and the goby leave the burrow together to search for food staying in close contact with each other. The fish have also been observed taking food back to the burrow for the shrimp and the two species have a complex inter relationship which is mutually beneficial for both parties. The burrows have been found to be up to two feet long, having numerous branches.
In some shallow areas on the west coast of Mafia Island we have observed the burrows to be completely out the water on a large spring tide and it is assumed that the goby and its shrimp companion head down the burrow which goes down into the water table, to wait the low tide out.
While the size of the burrow seems to correlate with the size of the shrimp, the size of its partner goby does not necessarily go along with the size of the goby. We have observed large shrimp with small gobies.
The Blue Speckled Shrimp Goby is found across the Indo west Pacific area from East Africa to Southern Japan, south to the Great Barrier Reef. They seem more common in areas of scattered sea grass in protected shallows.
The Blue Speckled Shrimp Goby feed on planktonic matter passing by their burrows. They have also been observed leaving their burrows and feeding on benthic organisms in the sea grass.
Mating takes place in a side corridor off the main burrow and the eggs are guarded in the side burrow by the male. The eggs hatch at night and the larvae exit the burrow, becoming planktonic.
Blue Speckled Shrimp Goby can be kept in aquariums but generally more colorful species of Shrimp gobies are kept in aquariums. If more than one is being kept then it is best to have a mated pair as the same sex gobies may fight.