Christmas Tree Worms (Spirobranchus Giganteus) are famous for making their permanent homes encased inside limestone skeletons of live coral.
Christmas Tree Worms © Nick Hobgood
The spiral ‘branchial crown’ serves as both breathing and feeding apparatus for the worm and is the only part of the worm’s body that is extended into the water column. The feathery appendages, known radioles, collect plankton that drift by the current, which is directed down the spiral to the worm’s mouth.