The largest fanworm crown on these reefs: a double spiral up to 6.5 cm (2.6 in) across in red, orange or white, rising from a hard white tube cemented to shaded rock. Unlike the christmas tree worms it does not live inside coral, and unlike them it has no trapdoor - when the crown retracts, the tube is simply left open.
That missing operculum is the quickest way to tell the group apart, and it says something about where the animal lives: a worm on a shaded wall has less to fear than one embedded in a coral head in full daylight. The crown filters plankton and fine particles from passing water and is exquisitely sensitive to shadow. Walls and overhangs below about 5 m (16 ft) are the place to look, usually as a splash of red against dark rock, and a slow approach is the only way to keep the crown out.
- large double spiral crown, red, orange or white
- hard white calcareous tube on rock, not buried in coral
- no trapdoor - the tube stays open when the crown withdraws
- crowns up to 6.5 cm across
