Christmas Tree Worm

Fascinating facts about the Christmas Tree Worm

• At just 3.8 cm (1.5 in) long, the Christmas tree worm lives inside a calcareous tube that can grow up to 20 cm, providing a fortress that the coral itself often overgrows, locking the worm safely inside. This extreme size disparity lets the worm stay hidden while its bright crowns wave in the water, turning a tiny animal into a permanent fixture of the reef's architecture.
• Each worm sports two spiral crowns made of feather-like, heavily ciliated radioles that act as both gills and nets, pulling microscopic prey from the flow and shuttling it straight to the mouth. The worm can stay completely sealed inside its tube, withdrawing its operculum plug when threatened, a strategy that lets it filter feed without ever leaving its coral home.
• The worm's life cycle is entirely marine: males and females release eggs and sperm straight into the water column, where fertilisation occurs and free-swimming larvae drift with currents until they find a suitable coral head to settle on. Once settled, the larva burrows into the coral skeleton and begins secreting its protective tube.
• Unlike many fan worms, the Christmas tree worm can seal its tube entrance with a specialized operculum that fits like a door. This plug is a modified radiole that snaps shut when the worm withdraws, a unique adaptation among Sabellida.
• Although the worm itself has no fishery value, its vivid crowns make it a favorite subject for underwater photographers and reef hobbyists, who often add coral heads inhabited by S. giganteus to miniature reef tanks.

Sources

Every fact above was checked against these pages, and kept only where one of them states it.

• Wikipedia

At a glance

About the Christmas Tree Worm

Christmas Tree Worms are marine polychaete worms that bore permanent tubes into living coral. The two vivid spiral crowns sticking out of the coral are not flowers, they are breathing gills that double as feeding fans, filtering tiny organisms from the water. They come in almost every colour imaginable.

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