Christmas tree worms are "polycheates", a sedentary worm living in hard corals. When they find a piece of live coral and burrow a home, they stay there.
They are small, about 3 - 4cm, but their bright colours and distinctive spiral shapes make them easy to spot. They can be found on hard coral formations in the reefs off Koh Lanta.
Their colourful "Christmas Tree" , feather like structures found on the surface of corals, are called Radioles. The main body of the worm in burrowed into the coral.
The feather like radioles, are the worms complex mouth appendages, allowing the worm to breathe and feed. By waving their feathers, they can catch passing plankton, moving it down to the mouth for eating.
The worms are very sensitive to movement and will retract in to their tubes if startled by shadows or moving objects. Wait a little, they will slowly open their tube and release their feathers.
Unlike other polycheates, Christmas tree worms have a third radiole, which covers the tube of the retracted worm, giving added protection. Although there are no real predators of adult worms.
This species reproduce by spawning and fertilising their eggs in the water, the larvae will then settle in the coral where it will burrow and grow into an adult.