A Polychaete is Not Just for Christmas

Christmas tree worms, otherwise known as Spirobranchus giganteus or Spirobranchus corniculatus (‘Spiro’ as in spiral, and ‘branchus’ as in lung) are species of polychaete worms that build a tube and are easily recognized by the spiral structures that rise above the corals they live inside. These structures are used for both respiration and feeding by the worms.As filter feeders, these worms use the feather like tentacles, also called radioles, to direct prey items toward and into the mouth. adioles can also be seen on other polychaete species such as feather duster worms.

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The “crowns” make up a 1/3 of the total length of the worm’s body, with the remainder inside a calcium carbonate tube that is usually grown over by the coral host species. Here on Koh Tao, we commonly find these worms growing on Porites or Montipora corals. But, a recent student visiting out program, Roel vaan der Shoot of the Naturalis Biodiversity Center published a short paper describing these worms as epibionts of Giant Clam species such as Tridacna squamosa.

Hidden beneath the surface of the corals is a tube that can measure up to 10 inches in length.
The worm builds the tube by excreting out calcium carbonate that its has gained through filter feeding. sand particles in particular are a great source of calcium. The tubes themselves offer protection for the worm should anything larger come along and try to feed on it. The worm is able to fully withdraw into the tube and use its operculum to block off the entrance allowing it to remain protected.

Despite their abundance in reef ecosystems, there is still very little work being done regarding the interaction they have with their host species. In some areas these worms can be found in incredible numbers which can potentially cause problems for the tissue of the host species.

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In high abundance they can essentially smother the coral, preventing the polyps from being able to gain energy through photosynthesis between zooxanthellae and the light penetrating the water column. They may also abrade the corals with their opperculumn when they retract to avoid predation, an effect that Roel is currently taking under study.

 Spirobranchus species have both male and female individuals and take part in broadcast spawning with the release of their eggs and sperm into the water column. Once fertilized the larvae will settle onto coral before beginning to bore their way into their new host.
The spawning of these gametes ties in with moon cycles, along with other species such as corals, clams, and crown of thorns and is just as mesmerising to observe.

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So the next time your swimming through a coral reef stop and take a minute to marvel at these amazing species. Not only are they bright and colorful and great for photographers, they are also important indicators of a healthy reef ecosystem

 

 

Spirobranchus species have both male and female individuals and take part in broadcast spawning with the release of their eggs and sperm into the water column. Once fertilized the larvae will settle onto coral before beginning to bore their way into their new host.
The spawning of these gametes ties in with moon cycles, along with other species such as corals, clams, and crown of thorns and is just as mesmerising to observe.

 

 

So the next time your swimming through a coral reef stop and take a minute to marvel at these amazing species. Not only are they bright and colorful and great for photographers, they are also important indicators of a healthy reef ecosystem

 

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New Heaven Reef Conservation Program