Christmas tree worms are so named because these marine worms have colourful spiral plumes that resemble a Christmas tree! They come in a variety of colours, like red, orange, pink, blue, white, yellow, and brown.
The “Christmas trees” are in pairs, attached to the same worm.
The plumes are radioles — hair-like appendages — measuring about 1.5 inches in length. Each worm has two of these “Christmas trees” to catch dinner and breathe. These worms use their radioles to catch phytoplankton and then pass the food to the worm’s mouth.
The Christmas tree is only a portion of the worm.
The rest of the worm is typically twice as long and bores into live coral. By ingesting sand and other calcium-rich particles, the worm excretes calcium carbonate to form a tube in the coral. The tubes can be eight to ten inches long — much longer than the worm itself. When they are startled, they fully retract into their burrows.
The lifespan of a Christmas tree worm varies greatly.
Depending on the size and health of the coral reef, the worms can live up to forty years, though the average is between ten to twenty years. They are popular for aquariums, though their lifespan in an artificial environment is much shorter.
There are male and female Christmas tree worms.
As broadcast spawners, they shoot their gametes into the water in the hopes that they will meet a match. Fertilized eggs become larvae. After nine to twelve days, they settle on a coral and begin to create their calcium carbonate tube.
We don’t know how Christmas tree worms choose their coral home.
Christmas tree worms appear to be selective about the coral reefs they choose, though more research on their selection process is needed. The jury is still out on whether or not these worms are helpful or a hindrance to their coral hosts.