The Pom Pom Crab (Lybia tessellata) also known as the Boxer crab and Mosaic Boxer Crab is a species of small crab in the family Xanthidae. As with other members of the genus Lybia they obtain their common names because of their habit of carrying a sea anemone around in each of their claws. These anemones in Tanzania are mainly Triactis producta which reportedly carry a powerful sting that can affect humans and do quite some damage despite their size.
They crabs are decapod crustaceans in the Infraorder Brachyura, in the Xanthidae family and are true crabs, they were first described by Latreille in 1812. They obtain their name from the mosaic pattern on the body with a tessellata being a tool used to make mosaics.
The Pom Pom crabs are small with a maximum width of 2.5 cm. The legs are a light brown/orange color with dark purple lines around them and numerous small white dots. The body is a darker brown color with geometric patterns created by dark brown lines making them a very attractive little crab. The front chelipeds have small claws that are well suited to carrying anemones in them and are effectively too small for any other purpose. They are surprisingly well camouflaged on some surfaces.
POM POM CRAB IN THE WILD
In Tanzanian waters we see rarely see the Pom Pom crab although they are likely very common. The deepest we have seen one is at 16 meters and they seem to come out and feed at night. They are very shy and generally shoot off into hiding at the sight of a diver. The anemones that they use in Tanzania are Triactis producta and these are reasonably common if one knows where to look for them. They are generally found in small crevices on the reef top in small communal groups.
The Pom Pom crab are found from the east coast of Africa including the Red Sea across to Japan in the north and eastwards to Hawaii.
Pom Pom crab use the anemones in their claws to gather plankton out the substrate and also use them to pickup food of the bottom, using them as mops. The crabs steal most of the food picked up by the anemones and in so doing control their size. They are omnivores but apparently prefer animal matter to plant matter. The front claws are not used for feeding at all, and the first pair of working legs are used for feeding.
The females are sometimes seen with a large red egg mass on the lower part of the body. The eggs hatch and undergo several stages before settling down on the sea floor. It seems no one has captive bred them yet.
The Pom Pom Crab are reportedly very easy to keep and are popular in nano tanks. Apparently they are suitable for beginners and are very peaceful and easy to feed as well as being fun to watch. They apparently can live for up to six years in an aquarium provided they are kept in a low competition environment.
POM POM CRAB CLASSIFICATION
Species: L. tessellata