Christmas tree worm

X-mas tree worm finds a home in Orbicella faveolata

Spirobranchus giganteus, commonly known as the christmas tree worm, has to be one of my favorite marine invertebrates. They are found commonly throughout the tropics but can be hard to spot since they are very small and quite shy. Living at depths ranging from ten to one hundred feet down. When startled they will quickly retract into their calcareous tubes.

The visible part that we see is called the crown and contains two spiraled plumes. If you look at the plumes from the side you can see why they get the name christmas tree worm. The rest of the worm is not visible, but altogether the worms body is bigger than what is visible. Like other worms in the phylum Annelida and class Polychaeta, they have parapodia and chatea. In other Annelids parapodia and chatae aid in motility but as an adult they are sessile, or not motile.

Photo's by Antonio Aidan Arruza

Sexual reproduction occurs when male and female worms release a lot of gametes into the water, called broadcast spawning. Once a larvae develops it finds a nice spot to settle. For a cool video on how they spawn check this out: spawning christmas tree worm.

The plumes have two functions, feeding and respiration. Christmas tree worms passively feed on suspended particles and phytoplankton using tentacles with pinnules attached for filtering food that flows by via currents.

pinnules visible (tiny yellow, brown, and white hairs sticking off the tentacles) 

Interestingly, when sand particles are caught the worm stores them for tube building. Their tubes can get up to around 8inches long. Crowns are only around one to one and a half inches big. Christmas tree worm vary in color but are usually varying shades of brown, blue, orange, white, and maroon.We learned about coral reef decline throughout the week and this could be bad for these guys since they rely on the coral as a place to live. One of the major causes of coral reef decline is ocean acidification, and for these guys this poses a double threat because of habitat loss and a more acidic, or lower pH, ocean. Since their tubes are calcareous, with decreasing pH this means they would not be able to make their tube without it dissolving. As an important indicator of reef health, christmas tree worms truly are "larger than they appear".