Two bright spiral crowns rising from the surface of a live coral head, each a helix of feathery filaments about 3.5 cm (1.4 in) across, in blue, orange, yellow or white. The worm itself is never seen: it lives in a calcareous tube built into the coral, and only the crowns are outside.
Those crowns do two jobs at once, straining plankton from the water and taking up oxygen, and they withdraw in a fraction of a second when a shadow crosses them - which is why photographing one means approaching slowly and waiting for the crown to reopen. A trapdoor called an operculum seals the tube behind it. This species was described from this sea in 2012, split off from the widespread Christmas tree worm on the strength of that trapdoor's shape, so what older guides here call Spirobranchus giganteus is frequently this animal instead.
- two spiral crowns rising from a live coral head
- crowns in a single colour - blue, orange, yellow or white
- vanishes into the coral instantly when a shadow passes
- crowns up to 3.5 cm across
