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  • Writer's pictureKim Hanlon

Oh Christmas Tree Worm, Oh Christmas Tree Worm...

How lovely are your... radioles.

We love them all year round, but 'tis the season to show some extra love to these little critters that brighten up any dive - from your very first open water experience to your 10,000th dive, from shallow reefs to up to 100 feet deep.

To celebrate their month, we have compiled some fun facts about these cute little buggers to share with you.

While the rest of us are digging into mince pies, chocolates and eggnog, our wormy friends prefer to chow down on plankton and other small particles that cruise by and get trapped in their plumes.

Not quite the hankering I get in the yuletide season, but each to their own... These pretty feathers are lined with both sticky mucus and spiky bristles (called cilia) , which not only helps to feed them, but also harnesses oxygen.

Think you've got it bad holed up in one place for lockdown? After conception and a little swim, Christmas Tree Worm babies build a calcium carbonate tube in the coral as their home, which take root like a tree and they can stay there for up to 40 years until their demise. And they don't even have Netflix! Just like a land tree, the colourful part of their bodies that we can see is just the tip. Along with their central tube, these worms have two spiraling structures called radioles that give them their tree-looking shape. You only can see the colourful feathery part of them, whilst anchored below the coral the rest of their bodies - the worm's legs (parapodia) and bristles (chatae) - are actually about twice as big.

Our wormy friends are notably good at doing as little as possible. Once they've chosen their forever homes, instead of doing some heavy drilling to set up shop, they nestle their bodies against the corals' living tissues, and force the polyps to build around them.

Work smarter, not harder! Occasionally though, they do have to do a bit of work to earn their keep. Spirobranchus ( their official Latin name ) are automatically enrolled into an environmental volunteer program from birth. Despite their small size, the presence of Christmas tree worms is crucial on coral reefs. They have an important role in keeping marine ecosystems healthy. They can protect the corals from invasive sea stars like the crown of thorns sea star and also help prevent the overgrowth of algae. Not only that, but it has been recently confirmed that they help coral reefs to recover after coral bleaching events.

That's some serious college credit right there!

If you've ever gotten a little too close a little too quick, you probably have noticed the Spiro's Houdini act. This is because they sense movement in the water and can retract when feeling threatened. It's not just curious divers they have to be alert for, but some predators that like to have a nibble on their flamboyant plumes include crabs, shrimp, urchins and even larger reef fish.

But they have to be quick!

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.

Enter at your own peril.

So essentially Christmas Tree Worms are a bit like moody teenagers, they mostly reside in their rooms, and just occasionally make an appearance to look pretty and get some fresh air and snacks.

Merry Christmas Tree Worm month, you filthy animals!


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