Christmas Tree Worms: Facts & Everything You Need To Know About This Colorful Aquatic Worm

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Christmas tree worm is a name that is commonly given to the Spirobranchus giganteus worm, belonging to the Sepulidae family. 

The reason these worms are so distinctive is because of their bright colors and interesting shapes. 

What are Christmas tree worms?

Christmas Tree Worms are colorful aquatic animals that live on coral reefs all around the globe. 

They have a very beautiful appearance resembling fir trees, with a variety of colors like 

•  yellow

•  blue

•  orange

•  white

• red 

It is their spiky shape, similar to a Christmas tree that gives them their popular name.

On average, christmas tree worms have an average size of 3.8 centimeters. 

The Christmas tree worms are found on the heads of corals. 

An interesting fact is that these worms are incredibly sedentary, which means that they often spend their entire lives in the same place. 

They live in waters that are less than 100 feet deep.

What do Christmas tree worms look like?

The body of the worm consists of a tube that is up to about 8 inches long and a crown. The worms are 1 to 1.5 inches in diameter. 

If you’re wondering what these worms look like, they are made most recognizable by the two shiny colored crowns that bulge out from their tube-like bodies. 


These crowns are composed of radioles, which are similar to hair-like appendages radiating from a central spine. 

The worms use these appendages to breathe and catch microscopic plants as food, which are floating in water or phytoplankton. 

While submerged in water these crowns help the worms to filter out tiny plants and animals for their food. 

These plumes have sticky mucus and cilia (Spiky bristles) which help them catch the prey. 

These visible pretty looking crowns not only help these worms to eat but also trap the oxygen and are often known as “grills”.



The worm generally produces their “tube” from excreting calcium carbonate that it absorbs from particles containing calcium or sand grains. 

The tube of the worm provides protection from predators as it is much longer than the worm. 

The worm withdraws into the tube when it feels like it is in danger and can seal it using an operculum or trapdoor. 

These opercula are equipped with spines for fending off predators.

How do Christmas tree worms feed?

Christmas tree worms filter feed using their plumes to trap microorganisms present in the water. 

This food is then directly deposited into their digestive tract. 

As these animals consume organic matter they are considered a decomposer.

How long do Christmas tree worms live?

Christmas tree worms are very picky about their corals and are largely sedentary. These worms don’t move much and live for around 40 years. 

Their life span largely depends upon the condition of the reef and the water in which they live. 

Since the worms spend their entire lives in the same area they do not move to find cleaner water or more favorable living conditions. 

So if the coral reef fails or the ocean is polluted the worms simply die out. 

Scientists believe that this coral species aids in the reproduction of the coral reef and attracts lesser predators.

How do Christmas tree worms reproduce?

Similar to many other aquatic species, Christmas tree worms are broadcast spawners. 

There are male and female Christmas tree worms that reproduce by releasing eggs and sperm into the water. 

Both the gamete contact and fertilization processes thus happen externally. 

Larvae are developed from fertilized eggs. 

Larvae live as plankton for 9-12 days before settling on a coral to produce a mucus tube that grows into a calcareous tube. 

Overall, broadcast spawning is quite effective and used by corals, oysters, and many other aquatic species. 

The timing of gamete release takes into account factors like currents, tides, water temperature, and the density of potential partners and mates available to reproduce.

Are Christmas tree worms under threat?

Human-caused climate changes and ocean pollution creates unfavorable conditions for tree worms. 

Broadcast spawning is triggered by changes in water temperature. If these natural cycles are altered because of global warming then their reproductive system is affected.

The common predators of these species are crabs, shrimps, and some tropical reef fish like butterflyfish. 

These predators generally eat the plumes of the worms and if some part remains intact, they have the capability to regrow within a few days.

Christmas tree worms respond quickly to threats by withdrawing into the tubes. They retract if they sense light changes, motion, or touch. 

They protect by sealing themselves in their operculum which is equipped with spines to fade off the predators. They reappear only when they sense that threat has passed. 


Christmas tree worms are thought to be stable and their populations are not considered endangered species. 

These worms are not yet harvested for food or for medical purposes but yet are considered popular amongst sea divers and underwater photographers. 

They may be harvested for aquarium businesses.

However, some potential threats for the survival of the worms include habitat loss due to climate changes and acidification of oceans which could lead to their loss of ability to build calcareous tubes. 

Their presence or absence indicates the well-being of the coral reef and water quality. 


Despite their colorful and wild appearance Christmas tree worms are nonpoisonous and pose no threat to humans. 

Their bright appearance attracts large numbers of marine photographers to the coral reefs they inhabit. 

Protecting this species of worm is important because of the essential role they play in the coral reef ecosystem.

Their inbuilt mechanism with its crown and tube system protects them from minor predators as they can simply pull themselves into the calcium carbonate tube and seal it off until the threat leaves. 

They live for around 40 years in a mostly sedentary lifestyle and their presence in a coral reef is an indication that the reef is healthy.