Christmas Tree Worm (Spirobranchus giganteus) Photo By Nhobgood Nick Hobgood – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6300216

Dear Readers, the Christmas Tree Worm is a feature of Caribbean and Indo-Pacific coral reefs, and quite the sight it is too. The worm burrows into large, live corals and makes itself a tube to live in. This might seem a bit harsh, but it’s thought that the Christmas Tree Worms might protect the coral from predators.  Once established, the worm sieves the water for plankton with its amazing feathery mouthparts (the ‘Christmas Trees’) – our humble limpet does much the same thing, though in a  much less spectacular fashion. Not only do the mouthparts absorb food and oxygen from the water, but they are also light-sensitive, so if the shadow of a predator passes over the worm can instantly withdraw into its tube. If something does take a bite out of the ‘Christmas tree’, the worm can regenerate it over time.

Each Christmas tree worm has two ‘Christmas trees’, so the photo above shows a single worm. There is a huge amount of variation between different worms, in terms of colour and size of appendage. A reef with lots of them is quite the sight to behold. And a single worm can live for up to forty years, a good age for an invertebrate.

Assorted Christmas Tree Worms (Photo By Nhobgood Nick Hobgood – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6262056)

When it’s time to breed, the Christmas Tree Worms release their eggs and sperm in to the ocean at the same time. Fertilised eggs soon become larvae and, if these aren’t eaten by fish they too will settle down on a coral and the whole cycle will start up again. The thought of seeing some Christmas Tree worms  is almost enough to make me think about digging out the wet suit again. Almost.

Indo-Pacific Christmas Tree Worm (Photo By (c) portioid, some rights reserved (CC BY-SA) – https://www.inaturalist.org/photos/331402951, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=146094517)

Orange Christmas Tree Worm (Photo By Nhobgood Nick Hobgood – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6262067)