---
title: Christmas Tree Worm (Spirobranchus giganteus)
scientific_name: Spirobranchus giganteus
common_name: Christmas Tree Worm
taxon: Annelid
published: 2023-12-24T05:17:35.893Z
updated: 2026-08-12T13:38:10.951Z
tags: Christmas Tree Worm, Spirobranchus giganteus, Annelid, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/worms/annelid/christmas-tree-worm
---

# Christmas Tree Worm (*Spirobranchus giganteus*)

## Quick facts

- **Group:** Annelid (*Annelida*)
- **Size:** crowns 2 cm across; worm to 4 cm
- **Depth:** 1-30 m
- **Diet:** Filter feeder
- **Activity:** Diurnal
- **Rarity:** Common
- **Habitat:** Embedded in living hard coral, mostly Porites heads
- **Reproduction:** Broadcast spawner, Gonochoric

## How to recognise it

- a pair of spiral crowns rising from a coral head, in almost any color
- vanishes instantly if a shadow or a hand comes near, then reappears
- the worm itself is never visible - only the crowns and a small trapdoor
- crowns about 2 cm across

Two spiral crowns rising out of a living coral head, in orange, blue, white, yellow or all of them at once. What is visible is a fraction of the animal: a tube worm sits in a calcareous tube built into the coral, and only the crowns come out.

The spirals do two jobs at once. They are gills, and they are a net - fine branches lined with beating hairs that trap plankton and move it down grooves to the mouth. The spiral shape packs the maximum filter area into the minimum diameter, which matters when the animal has to fit its whole apparatus back down one small hole.

The disappearing act is a reflex, not a decision. Light and pressure sensors in the crowns fire directly into the muscle, the worm is inside in a few milliseconds, and it seals the tube behind it with a plug tipped with spines. Divers who wait a minute and stay still get the second show, which is the crowns unfolding again.

The color means nothing. Crowns come in orange, blue, white, yellow, brown and combinations of them, and the variation is individual: it does not mark sex, age, health or the species of coral underneath. Two worms a centimeter apart on the same head are routinely different colors, and the assumption that blue ones are males is folklore.

Sexes are separate and impossible to tell apart from the outside. Everything sexual happens in the abdominal segments deep inside the tube; in a worm removed from its tube the ripe gametes show through the body wall, pinkish in females and pale in males, and that is the only way anyone can tell. Spawning is done blind and into open water: both sexes release gametes through pores near the crown, fertilization happens in the water column, and the larvae drift for a week or two before settling. A larva that settles on live coral is the one that survives - the colony then grows up around the young tube, which is why a head studded with a dozen crowns is a partnership decades old, and why they die when it does.

## Also known as

- **English:** Christmas tree worm, Horned Feather Worm, spiral-gilled tubeworm
- **German:** Bunter Spiralröhrenwurm, Spiralröhrenwurm, Tannenbäumchen-Röhrenwurm
- **Japanese:** イバラカンザシ
- **Russian:** Спиробранхус гигантский

## Scientific synonyms

- *Cymospira bicornis* (Abildgaard, 1789)
- *Cymospira cervina* Quatrefages, 1866
- *Cymospira gigantea* (Pallas, 1766)
- *Cymospira megasoma* Quatrefages, 1866
- *Cymospira rubus* Quatrefages, 1866
- *Olga elegantissima* Jones, 1962
- *Penicillum marinum* Seba, 1758
- *Pomatoceros oerstedi* Voss & Voss, 1955
- *Serpula (Cymospira) gigantea* Pallas, 1766
- *Serpula (Galeolaria) gigantea* (Pallas, 1776)
- *Serpula bicornis* (Abildgaard, 1789)
- *Serpula gigantea* Pallas, 1766
- *Spirobranchus (Cymospira) giganteus* (Pallas, 1776)
- *Spirobranchus giganteus giganteus* (Pallas, 1766)
- *Spirobranchus giganteus microceras* Mörch, 1863
- *Spirobranchus giganteus tricornis* Mörch, 1863
- *Spirobranchus megasoma* (Quatrefages, 1866)
- *Spirobranchus tricornis* Mörch, 1863
- *Terebella bicornis* Abildgaard, 1789

## Range

Caribbean Sea, Gulf of Mexico, Hispaniola, Indian Ocean, Mozambique, Red Sea

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/worms/annelid/christmas-tree-worm)*
*Updated: August 12, 2026*