A flattened pale crab with dark bands across the legs, living between the branches of Acropora. About 1.5 cm (0.6 in) across, it slides sideways along a branch when approached rather than dropping deeper into the colony the way its Pocillopora-dwelling relatives do.
The division is worth knowing: crabs of this genus keep to Acropora, Trapezia to Pocillopora and Stylophora, and finding one tells you which coral you are looking at as surely as the coral tells you which crab to expect. Both act as bodyguards, driving off coral predators and clearing sediment from the branches, and both are paid in mucus. A colony without its crabs suffers measurably more damage from crown-of-thorns and smothering silt, which makes these animals a good example of a partnership that is easy to overlook and hard to replace.
- flattened pale body with dark banding on the legs
- lives in Acropora, not in Pocillopora
- moves sideways along a branch rather than backing away
- width up to 1.5 cm
