Keelworm Spirobranchus triqueter

Keelworm Spirobranchus triqueter

Class Polychaeta (Bristle worms)
Order Sabellida
Family Serpulidae (Serpulids)
Species Spirobranchus triqueter (Linnaeus, 1758)

Tube width 3-5 mm.
Worm length up to 25 mm.

The tube in which the worm hides at low tide is white and smooth, irregularly curved, hard and calcareous with a single prominent ridge along its back. It looks triangular in cross-section. The worm itself is small with varied colouration,  and has a crown of feeding tentacles. Similar to Pomatoceros lamarcki which has two ridges each side as well as a centre ridge.

Seen all year round, encrusting and scarring rocks and shells on the middle to lower shore. Discovered on most types of coastline. Common and widespread on all coasts.

Meadfoot Beach, Torquay, Devon August 2015. © Peter Hillman.