Christmas Tree Worm

Details

Spirobranchus giganteus—the Christmas tree worm—is a tube‑dwelling serpulid polychaete with two vividly coloured, spiral radiolar crowns for filter feeding and gas exchange. After settlement it secretes acalcareous tube, remains sessile and rapidly retracts when disturbed, sealing the tube with an operculum.

Ecology & Biology

• Life habit: sessile tube‑builder; only crowns and operculum are exposed.

• Feeding: ciliary/mucus‑based suspension feeding on micro‑plankton and POM.

• Coral association: often embedded in living coral skeletons; interactions range from commensal to mildly competitive.

• Reproduction: external fertilization; planktonic larvae settle and metamorphose into adults.

Identification

Body inside a white/beige calcareous tube; crowns show diverse colours (yellow, orange, red, blue, white), sometimes different between the two spirals. The operculum may carry spines/coronet and varies geographically.

Size & Longevity

• Tube length: typically 2–4 cm (up to ~5–6 cm); crown diameter 2–5 cm.

• Life: generally several years, longer on stable reefs.

Range & Habitat

Widespread on tropical Indo‑Pacific and Atlantic reefs (Red Sea, Caribbean included), favouring well‑lit reef flats, slopes and lagoons around ~1–25+ m.

Roles & Threats

• Roles: abundant small suspension feeders recycling particulate carbon and providing microhabitats.

• Threats: reef degradation, sedimentation and pollution; mass coral bleaching indirectly affects recruitment/survival.

IUCN: marked here as Not Evaluated (NE).