Crabs Make Coral Castles

a crab next to a coral den
García-Hernández, J.E., de Gier, W., van Moorsel, G.W.N.M. et al.

To avoid predators, gall crabs form depressions in living coral, a small pit or cave that the crab then lives in. The home also provides easy access to food. The crabs feed on mucus that the coral produces and also other algae bits that they can reach from inside their small coral caves.