The Christmas Tree Worm, scientifically known as Spirobranchus giganteus, is a type of tube-building polychaete worm.
It belongs to the family Serpulidae and is found in tropical oceans all over the world.
This worm is named for its two colorful spiral structures that look like Christmas trees.
What Does a Christmas Tree Worm Look Like?
A Christmas Tree Worm has a tubular, segmented body that is about 1.5 inches (3.8 cm) long.
It’s covered with small appendages called chaetae, which help it move.
The most distinct features of this worm are its two ‘crowns’ that resemble Christmas trees.
These crowns are made up of feather-like tentacles called radioles, which the worm uses for feeding and breathing.
How Does a Christmas Tree Worm Feed and Breathe?
The worm’s radioles are heavily ciliated, meaning they have tiny hair-like structures that move.
When the worm catches prey in its radioles, the cilia transport the food to its mouth.
The radioles also act as the worm’s gills, allowing it to breathe underwater.
Where Can You Find a Christmas Tree Worm?
These worms are found in tropical oceans across the globe, from the Caribbean to the Indo-Pacific.
They usually live embedded in massive corals, such as stony corals and brain corals.
How Does a Christmas Tree Worm Protect Itself?
Christmas Tree Worms secrete a calcareous tube around their bodies, which serves as their home and protection.
They often settle onto living coral before making their tube, so the coral tissue grows over it.
When a worm needs to hide, it can retreat into its tube and close the opening with a special structure called an operculum.
What Is the Christmas Tree Worm’s Role in The Ecosystem?
As sedentary inhabitants of coral reefs, these worms primarily feed by filter feeding.
They use their radioles to catch microorganisms from the water and deposit them into their digestive tract.
Few organisms are known to eat tube-dwelling polychaetes like the Christmas Tree Worm.
The relationship between these worms and their host corals is not well understood, but their movement can sometimes cause damage to the coral tissue.
Why Are Christmas Tree Worms Important to Humans?
Although they don’t have any commercial value, Christmas Tree Worms are popular with marine aquarists and divers.
Their colorful crowns make them attractive subjects for underwater photography.
Many people who keep small reef aquariums purposely include coral heads that are home to these worms.
What Is the Conservation Status of The Christmas Tree Worm?
Since the species is widespread and relatively common, there are no specific conservation efforts focused on Christmas Tree Worms.
Their host species, however, may have varying conservation statuses.
What Are the Subspecies of Christmas Tree Worm?
There are two recognized subspecies of the Christmas Tree Worm:
- Spirobranchus giganteus corniculatus, and
- Spirobranchus giganteusa giganteus.
The name “Spirobranchus” essentially means “spiral gills,” referring to the worm’s unique crown shape.
Christmas Tree Worm Characteristics
| Reef Safe? | Yes |
| Care Level: | Expert |
| Maximum Size: | 2.0 in (5 cm) |
Scientific Classification
| Kingdom: | Animalia |
| Phylum: | Annelida |
| Order: | Sabellida |
| Family: | Serpulidae |
| Genus: | Spirobranchus |
| Scientific Name: | Spirobranchus giganteus |
| Also Known As: | Christmas Tree Worm |
| Conservation Status: | Unknown |