Science of the Day I

Worms : The Christmas Trees of the Deep

Published by JK Kristie
July 26, 2009, Category: Marine Biology

Who would have thought that worms can be so beautiful?

Who would have thought that worms can be so colorful?

Found on coral reefs in tropical waters worldwide, these worms are not only the most interesting looking; they also are the most beautiful.

Spirobranchus giganteus, commonly called as Christmas tree worms are small Christmas tree-shaped serpulid tube-dwelling worm with spectacular twin spirals of plumes used for feeding and respiration. Though tiny in its less than 1 ½ in (3.8 cm) size, its cone-like shape and magnificent twin spiral plumage called radioles makes it widely admired and easily recognized by divers.

Spirobranchus means “spiral gills”, referring to the worms unique crown.

Christmas tree worms come in a wide variety of colors including orange, yellow, blue and white as well as different color combinations. Though the spectacular plumes are visible, most of the worm’s body is anchored in its burrow that it bores into live calcareous coral. These undersea creatures are ultra sensitive to disturbances that even a passing shadow can cause an instant retraction into its hideaway. The plumes usually re-emerge about a minute later, very slowly, to test the water before fully extending all its glory.

They are commonly found embedded in entire heads of massive corals. Like members of its family, serpulidae, it can secrete a calcareous tube around its body, which serves as its home and protection.

Spirobranchus giganteus are filter feeders—they use their beautifully-colored radioles to filter microorganisms in the water, which are then delivered straight into their digestive tract.

These sedentary inhabitants of the deep reproduce by casting their eggs and sperm into the water where they are fertilized and develop into larvae that settle on coral heads and burrow into the coral.