Keelworm (Tubeworm)

Spirobranchus triqueter

What do they look like?

Keelworms live inside a white, twisting, calcareous tube that they create themselves. These tubes are smooth, with a ridge that runs along the top. They encrust rocks, shells, and various other hard marine surfaces. The worm that lives inside each tube will vary in colouration between individuals, but each possesses a crown of tentacles which it uses to feed on the plankton and detritus that float by on the currents.

Where can I find them in Scotland?

They can be seen on all coasts across Britain and Ireland. They prefer sublittoral habitat (below the shore) and can occur at depths of 70 meters or above. You can find them in the middle to lower shore on rocky coasts or on shells and pebbles washes up by the waves.

Up to 25mm long and 3.5mm wide
1.5 - 4 years
Conservation Status

Fun Fact
Male and female keelworms can be told apart by their colour. Male worms are a creamy colour, whereas females can be bright orange or pink (note that their calcareous tubes are not this colour)!

When rockpooling, please be careful to leave everything as you found it.

Discover more about how to rockpool responsibly by watching our Beginner's Guide.

Cream-coloured, calcareous keelworm tubes encrust a wet, sandy rock in wavy patterns
© Susan Davies