A small anemone, under 2 cm (0.8 in), with tentacles gathered into knobbed clusters - and the animal at the centre of one of the better double acts on the reef. Boxer crabs carry one in each claw and hold them out like pom-poms, using the anemone's stinging cells as a weapon they do not have to grow themselves.
The arrangement is not a partnership of equals. The crab feeds by wiping the anemones over the substrate and taking what sticks to them, so the anemone loses part of its catch, and a crab deprived of one will tear its remaining anemone in two rather than go without - both halves regrow, which is where new anemones for the trade come from. Free-living individuals do exist, in rubble crevices, and a diver more often finds them that way than by spotting the crab, which is nocturnal and secretive. Stinging power is out of all proportion to size, and that is exactly why the crab wants it.
- tiny, under 2 cm, with knobbed tentacle clusters
- often seen gripped in the claws of a small crab
- translucent brown with white-tipped clusters
- free individuals sit in rubble crevices
