In Florida’s coral reefs, it is Christmas year-round with an abundance of Christmas tree worms! Scientifically known as Spirobranchus giganteus, these tropical worms are identifiable by their spiral plumage, bright color, and skittish behavior. The spiral arrangement of their plumage is what earned them the name Christmas tree worm, since they closely resemble fir trees. Their plumage is known as ‘radioles’, which spiral in two ‘crowns’ around their tube-shaped body. Radioles are tentacles used for both respiration and feeding.

Christmas tree worms are sessile organisms, meaning they are attached to a base that prevents them from moving around. Once that base attaches to a surface, the worm will likely remain on that surface for the rest of its life. Their inability to move does not prevent them from eating, as the ocean’s currents will bring the food to them.

Phytoplankton are the main food source for Christmas tree worms. These are microscopic plants that float throughout the water column and serve as food sources for many marine organisms.  As they drift past the worm, phytoplankton stick to the ends of the worm’s radioles and are transported to its mouth. 

They live in a tube that can be up to ten inches long and provides protection from predators. At the end of the tube, Christmas tree worms have an operculum, a hard, plate-like door. When disturbed, these worms rapidly retreat into their tube, tucking in their radioles and sealing the entrance with their operculum. When they feel safe, they will timidly open that operculum and poke their radioles out to make sure the coast is clear.

Despite only sitting about an inch and a half above their protective tube, these worms have made an impact on all who explore the coral reefs they call home. Their bright colors and eccentric tree-like shape make them stand out amongst the busy reef and add to the allure that attracts millions of people to visit and snorkel above them.

Article by Izzy Lutz

Sources

(1) https://www.inaturalist.org/taxa/49519-Spirobranchus

(2) https://oceanservice.noaa.gov/facts/xmas-tree.html

(3) https://oceana.org/marine-life/christmas-tree-worm/

(4)https://newheavenreefconservation.org/8-blog/158-a-polychaete-is-not-just-for-christmas#:~:text=Hidden%20beneath%20the%20surface%20of,a%20great%20source%20of%20calcium.

(5)https://www.cambridge.org/core/journals/journal-of-the-marine-biological-association-of-the-united-kingdom/article/substrate-selection-of-christmas-tree-worms-spirobranchus-spp-in-the-gulf-of-eilat-red-sea/CBEDA606343BDBA72CD1CAF21C309C6F

Foreword by Jordyn Sateren:

Christmas tree worms are just the best! They combine my love for Christmas with the love for super tiny cool and weird things you can find living along a coral reef. While scuba diving along coral reefs, it’s one of my favorite things to observe these little creatures displaying their bright colors in the shape of little trees on coral heads. When you swim near the coral the worm’s beautiful display of colors will all of a sudden suck back into the coral for protection, then if you are patient enough they will pop back out for you to see again. It’s a great reminder of how the creatures along the reef are interacting with you as much as you are interacting with them.