On the tropical reefs of Western Australia the stunning Neopetrolisthes maculatus is always found living on or around large sea anemones. Like the clown fish, these spotty little crabs are protected from potentail predators by the stinging tentacles of the sea anemone. Only a single pair of crabs can be found on each host as the crabs will defend their territory from rivals. Despite their impressive claws these are not used for capturing food, but are probably used fend off potential home invaders. Neopetrolisthes maculatus is actually a filter feeder; their mouthparts have long setae (bristles) which they use like a broom to sweep small organisms, like planktonic algae and crustaceans, out of the water column.
These crabs belong to the family Porcellanidae, which are often called porcelain crabs, half crabs or false crabs. While superficially resembling the so-called true crabs, like the blue swimmers or ghost crabs, they are actually more closely related to the hermit crabs. Unlike the true crabs, the abdomens of porcelain crabs still retain a tail fan similar to that of lobsters or shrimp. The abdomen is very mobile and when the crab is threatened they flick the abdomen to swim out of danger. The porcelain crabs also possess a pair of very long whip-like antennae whereas the true crabs have only a small stumpy pair between the eyes.
From top to bottom: Neopetrolisthes maculatus sitting amongst the tentacles of sea anemones on Hibernia Reef, Kimberley and the Montebello Islands and a preserved specimen collected during the Museum’s recent survey of Scott Reef.