Learn About the Life and Times of the Christmas Tree Worm

The Christmas Tree Worm is a colorful marine worm with beautiful, spiraling plumes that resemble a fir tree. These animals can be a variety of colors, including red, orange, yellow, blue and white.

The "Christmas tree" shape shown in the image is the animal's radioles, which can be up to about 1 1/2 inches in diameter. Each worm has two of these plumes, which are used for feeding and respiration. The rest of the worm's body is in a tube in the coral, which is formed after the larval worm settles on the coral and then the coral grows around the worm.The worm's legs (parapodia) and bristles (chatae) protected within the tube are about twice as large as the portion of the worm visible above the coral. 

If it worm feels threatened, it can withdraw into its tube to protect itself.

Classification:

• Kingdom: Animalia
• Phylum: Annelida
• Class: Polychaeta
• Subclass: Canalipalpata
• Order: Sabellida
• Family: Serpulidae
• Genus: Spirobranchus

Habitat of the Christmas Tree Worm

The Christmas tree worm lives on tropical coral reefs throughout the world, in relatively shallow waters less than 100 feet deep. They seem to prefer certain coral species. 

The tubes that Christmas tree worms live in can be up to about 8 inches long and are constructed of calcium carbonate.The worm produces the tube by excreting calcium carbonate that it obtains from ingesting sand grains and other particles that contain calcium. The tube may be much longer than the worm, which is thought to be an adaptation that allows the worm to withdraw fully into its tube when it needs protection. When the worm withdraws into the tube, it can seal it tight using a trapdoor-like structure called an operculum. This operculum is equipped with spines to fend off predators.

Feeding

The Christmas tree worm feeds by trapping plankton and other small particles on their plumes. Cilia then pass the food to the worm's mouth.

Reproduction

There are male and female Christmas tree worms. They reproduce by sending eggs and sperm into the water. These gametes are created within the worm's abdominal segments. Fertilized eggs develop into larvae that live as plankton for nine to 12 days and then settle on coral, where they produce a mucus tube that develops into a calcareous tube. These worms are thought to be capable of living over 40 years.

Conservation

Christmas tree worm populations are thought to be stable. While they aren't harvested for food, they are popular with divers and underwater photographers and may be harvested for the aquarium trade.

Potential threats to the worms include habitat loss, climate change and ocean acidification, which could affect their ability to build their calcareous tubes. The presence or absence of a healthy Christmas tree worm population can also indicate the health of the coral reef. 

Sources

• De Martini, C. 2011. : Christmas Tree WormSpirobranchus sp.. Great Barrier Reef Invertebrates. University of Queensland. Accessed November 29, 2015
• Frazer, J. 2012. The Overlooked Joy of the Christmas Tree Worm. Scientific American. Accessed November 28, 2015.
• Hunte, W., Marsden, J.R. and B.E. Conlin. 1990. Habitat selection in the tropical polychaete Spirobranchus giganteus. Marine Biology 104:101-107.
• Kurpriyanova, E. 2015. Exploring the Diversity of Christmas Treet Worms in Indo-Pacific Coral Reefs. Australian Museum. Accessed November 28, 2015.
• Nishi, E. and M. Nishihira. 1996. Age-estimation of the Christmas tree worm Spirobranchus giganteus (Polychaeta, Serpulidae) living buried in the coral skeleton from the coral-growth band of the host coral. Fisheries Science 62(3):400-403.
• NOAA National Ocean Service. What Are Christmas Tree Worms?
• NOAA Encyclopedia of the Sanctuaries. Christmas Tree Worm.
• SeaLifeBase. (Pallas, 1766): Christmas Tree WormSpirobranchus giganteus. Accessed November 29, 2015.
• University of Queensland. Great Barrier Reef Invertebrates: Spirobranchus giganteus.