Christmas Tree Worm

The Christmas tree worm is a small reef animal with a surprisingly architectural appearance. Each Spirobranchus giganteus displays two spiraling crowns above a hard tube. The paired crowns can be orange, white, brown, maroon or mixed in color. They belong to one segmented worm, not to a tiny coral colony, and most of that animal remains concealed below the visible spirals.

Local South Florida evidence

A published underwater photograph collection identifies living Christmas tree worms at the Benwood wreck and French Reef off Key Largo. These provide specific Upper Keys field records rather than relying on a broad Caribbean range. Farther north, the 2014 St. Lucie Inlet Preserve State Park inventory lists the species. That inventory is historical evidence, not a current census or a guarantee of visibility on a Stuart dive.

Think of this as a reef and hard-substrate subject, not a sand-flat burrower to seek by disturbing the bottom. A colony of host coral may support several worms, but two adjacent crowns can be the feeding apparatus of a single animal. Take time to trace the pairing visually without touching the surrounding coral.

How the crowns work

The finely divided structures are called radioles. They help the worm exchange gases and intercept food suspended in passing water, including microscopic phytoplankton. A stationary animal can therefore feed without chasing its meal. The attractive “trees” are working body parts, not decorative growths.

When startled, the worm can pull the crowns into its tube. A protective lid, the operculum, closes the opening; the Caribbean identification guide describes its two horn-like projections. An animal that disappears has not detached from the coral or vanished into another burrow. It has withdrawn into its own shelter.

Reproduction and recognition

Christmas tree worms reproduce by releasing eggs and sperm into the water. Their larvae spend a period in the plankton before settlement. This general life history does not establish a particular spawning month for Key Largo, so no local breeding calendar is implied here.

Look for two tightly spiraled crowns, rather than the more open fans of many feather-duster worms. Color alone is not a species diagnosis. If photographing one, make a wide habitat image and a closer view from the same non-contact position. Avoid repeatedly waving a hand over it to force retraction.

Responsible diving

Do not chip coral or pull out a worm to see its tube. FWC regulates marine-life collection and prohibits harvest of stony corals; local sanctuary and park restrictions also matter. Enjoy this animal in place and consult the applicable current rules rather than treating an identification guide as collecting permission.

References

• Key Largo field photographs: Benwood and French Reef
• 2014 St. Lucie preserve inventory
• NOAA: Christmas tree worm feeding and crowns
• Naturalis Caribbean guide: tube and operculum
• Oregon Coast Aquarium: reproductive life history
• FWC marine-life rules

Collection and habitat protection

Calcareous tube worms are regulated marine life. Do not chip host coral or remove live rock; FWC prohibits stony-coral harvest and recreational live-rock harvest. Current FWC marine-life guidance. Guidance reviewed November 12, 2026. No location-specific collection clearance is given.

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