'The Christmas Tree Worm'
(Natural History Episode 5)
Christmas tree worms (Spirobranchus giganteus) are an abundant creature on Floridian reefs, making their permanent homes encased inside the limestone skeletons of live coral. Found in a seemingly endless variety of colors and measuring 2-3 cm in diameter, dozens of these worms will typically adorn massive coral heads in local waters.
Using only the perception of light and vibration, these animals will retract at lighting speed at the first sense of something ominous approaching. Fortunately the worms come equipped with a a protective double-horned operculum that seals the worm safely inside the inpenetrable coral. A sharp, calcareous spike extends forward of the tube's opening, acting as a further deterant to a would-be predator.
The spiraled, '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 in the current. The radioles are lined with cilia that direct the captured food down the spiral to the worm's mouth.
Video, Aquarium + Original Soundtrack: Coral Morphologic
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