California Sandcastle Worm

Phragmatopoma californica

California Sandcastle Worms, known scientifically as Phragmatopoma californica, are dark brown polychaete worms that can grow up to 7.5 centimeters in length. They are characterized by a crown of lavender tentacles that they extend from their tubes to capture food particles. These worms inhabit the Californian coast, ranging from Sonoma County to northern Baja California, and are commonly found in colonies that build tube reefs resembling sandcastles. These structures can cover areas up to 2 meters on each side and are typically located on rocky beaches at medium to low tide, often alongside mussel beds and in sheltered areas such as rock faces and overhanging ledges. California Sandcastle Worms are sessile and remain within their tubes, where they close the entrance with a shield-like operculum when exposed to air. They primarily feed on plankton and organic matter, filtering food particles from the water using their tentacles. The larvae of these worms undergo a pelagic development phase before settling, which is influenced by chemical cues from existing colonies. They require contact with adult tubes to metamorphose into adults, highlighting their gregarious settlement behavior. When diving, encounters with these worms may involve observing their distinctive tube structures, but the worms themselves are rarely seen as they remain hidden within their tubes. The species has not been evaluated by the IUCN, and its conservation status is currently listed as Not Evaluated.