Worm Tubes or Scaly Tube Snails (Serpulorbis squamigerus) ~ Worm tubes are a mollusk or sea shell that are attached in colonies to rocks from low intertidal to 65 ft. deep water. Special cells produce the calcium carbonate that is used to construct the tube. They have a black operculum (or trap door) which covers the tube; when threatened, they can withdraw into their tubes and close off the opening.  The opening is closed when the tide is out and the animal is out of the water.   To eat, worm tubes secrete a mucus to capture tiny drifting particles.  They are prey for some of the drilling shells like the Pteropurpura festiva which can drill a hole through the tube and eat out the worm tube animal.