Posted by Mead Krowka | 12.20.2022 | Sea Turtle Camp News

Trivia Tuesday- Christmas Tree Worms

Happy Holidays! To ring in Christmas, we thought there was no better Trivia Tuesday topic than Christmas Tree Worms!

What are they?

The Christmas Tree Worm – also known as Spirobranchus giganteus – exists as a marine segmented burrowing worm.  These are some of the most popular polychaete or marine segmented burrowing worms. Each worm has two brightly colored appendages (known as crowns) that protrude from its tube-like body. These are composed of radioles, or hair-like strings extending from the worm’s central spine that are used for respiration and feeding.

Where do they live?

Although festive, you won’t find these worms at the North Pole!  They are most commonly found on reefs ranging in tropical waters from the Caribbean to the Indo-Pacific. They can be found embedded in stony corals, such as Porites and brain corals. Once they select a home, they burrow in and create a calcareous tube, which provides protection. Christmas Tree Worms are sedentary – this means that once they find a burrow in a head of coral, they tend not to leave. When undisturbed, the two crowns are exposed, showing a colorful array among the corals. However, when a curious fish or interested diver comes a bit too close, they quickly retract into their burrow.

What do they eat?

Due to their sedentary lifestyle, Christmas tree worms cannot move around to find food. This is where the crowns come into play. The radioles are covered in hundreds of cilia, allowing them to capture planktonic particles floating by, often exclusively phytoplankton. Once contact is made with the radioles, the cilia transport it down to the mouth of the worm.

Why are they important?

Although there is no commercial importance, Christmas Tree Worms are crucial for the reef ecosystem. They consume algae that can harm corals, preventing them from overgrowing and suffocating the polyps. They also help to keep some invasive species off corals, such as the Crown of Thorns sea star. Christmas Tree Worms also draw the attention of divers and snorkelers.  With their vibrant array of colors, you can see them commonly featured in underwater reef photography. As the species are widespread and fairly common, they are not under any specialized conservation.