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Fun Facts about Christmas Tree Worms

[Phylum: Annelida] [Clade: Pleistoannelida] [Family: Serpulidae] [Species: Spirobranchus giganteus]

Christmas tree worms are sedentary tube-building polychaetes of the phylum annelida that live almost exclusively on large stony brain corals and Porites compressa (finger coral).

This section contains facts and information about Spirobranchus giganteus, including where they thrive best, what they eat, and how these invertebrate tube-dwellers reproduce.

Spirobranchus Giganteus Habitat and Range

The best place to find Christmas tree worms is the shallow waters (not deeper than 30 metres) of tropical oceans.

As a matter of fact, they are superabundant in the Indo-Pacific regions and around the Caribbean Sea.

Here's the thing:

Unlike most marine annelids, tree worms are sedentary creatures living inside a tube. They can't swim, float, or move around the ocean.

Instead, they anchor themselves to hard stony porites (brain corals).

Because these multicoloured, cone-shaped, spiral structures never completely leave their tube, the Christmas tree worm relies on flowing water currents to provide them with nutrients.

Its "helter skelter" tree-shaped cone extends outside the central tubular spine, filtering suspended microorganisms and floating food particles (called phytoplankton).

The outcome...

Being a typical omnivore means they are a "sit and wait for it" creature. Unlike the voracious predator, the bearded fireworm (Hermodice carunculata), these tiny tree worms are certainly not deadly scavengers.

The popular name of the species comes from its festive, fir tree appearance - not its diet or habitat. Yet, to some it is simply known as a sea worm.

Christmas Tree Worm Characteristics

The tubular segments of the Christmas tree worm species are lined with tiny appendages (called chaeta) that help with movement in and out of its tube. By and large, these calcareous tubes grow up to four centimetres long (1.5 inches).

As it extends outwards, the multicoloured spirals create feeding structures and function as a respiratory system or gills.

Christmas Tree Worm Facts and Information (Spirobranchus giganteus)Christmas tree worms are ciliary feeders - meaning they filter their food from the water column.

But wait - there's more:

They have tiny hair-like feathers which form circles protruding outwards from the central spine.

These structures also contain plumes of feather-like ciliated radioles which trap prey and guide it towards the mouth and digestive tract, called a prostomial palp.

Anatomy of Spirobranchus Giganteus

The vast majority of Christmas tree tube worms are magnificent chromatically hued species of the phylum annelida (ringed worms). They have a fully functional digestive system and a well-developed circulatory system.

Its central brain facilitates an efficient nervous system. Like most polychaetes, they excrete waste matter through a nephridium (the equivalent of a kidney in marine invertebrates).

In case you were wondering:

Touching it, light changes, and any undue motion will ensure that it retracts from life - momentarily disappearing out of sight until the perceived danger, or disturbance is gone.

Sport divers need patience to see S. giganteus at their best. But, they often lose some of their tiny appendages to fish nipping at them before they can retract back inside the safety of the tube.

Calmly wait a few moments and the organism will usually re-emerge, unfurling cautiously and "testing the water" before it fully expands its beautiful spiral feather plumes and vivid colours.

Christmas Tree Worm Fun Facts

Christmas Tree Worm Reproduction

During reproduction, males and females shed their "gametes" directly into the sea. The casting of male sperm cells into the water coincides with the release of eggs from the females.

If fertilisation is successful, the eggs drift along with zooplankton in the ocean currents while they develop into tiny larvae.

When their larvae find a coral head in which to settle, the microscopic baby Christmas tree worms settle and begin burrowing tiny holes to create their distinct tube-like dwellings.

Threats and Predators

Christmas tree worms are not harmful to human life. But, their natural predators include most large crustaceans, crabs, and some echinoderms (e.g. sea urchins).

They have no obvious fishery or culinary importance. However, their multicoloured crowns of orange, blue, yellow, and white make them a favourite with some fishkeeping hobbyists, and they are popular photographic objects for scuba divers and snorkelers.

Important: The IUCN Red List of Threatened Species is a comprehensive source of information about the global conservation status of animals, fungi, and plants. Currently, the IUCN lists Spirobranchus giganteus as stable but under threat in some areas due to uneducated divers.

Related Information and Help Guides

Note: The short video [1:29 seconds] presented by "ContentMint" contains footage of a Christmas Tree Worm (Phylum Annelida) retracting into its tube and re-emerging to feed.

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