Details
Spirobranchus giganteus
The Christmas tree worm is a reef polychaete with two bright spiral crowns. Hidden in a calcareous tube, it filters food from passing water.
Map: Ecoregions 2017 © RESOLVE (CC BY 4.0) · Natural Earth (PD)
It lives on coral reefs of the Atlantic, Indian, and Pacific oceans. Calcareous tubes are built in living coral or hard rock where light and current are available.
Length 1.5-4 cm; weight 0.2-3 g. Most of the body stays inside the tube, while two spiral feeding crowns protrude like miniature trees. Colors include red, blue, yellow, white, and many mixes.
Diurnal and solitary, it spreads the crowns to feed. Shadows or vibration trigger a rapid withdrawal into the tube.
A filter-feeder, it uses fine hairs on the crowns to trap plankton and organic particles. Captured particles are carried to the mouth.
Adults release eggs and sperm into the water. Larvae drift before settling on coral or other firm substrate and extending a tube.
It is listed as Least Concern. Because it depends on reefs, bleaching and heavy sediment can affect local populations.
