[2] Serpula vermicularis lives in a calcareous tube which is attached to a rock, boulder or other hard surface.

The anterior part of the worm protrudes from the tube and has a plume of about 40 feather-like radioles projecting from the second segment, or peristomium, which also houses the two eyes and the mouth.

A funnel-shaped lid or operculum covers the entrance to the tube when the animal retracts inside.

The tube is fabricated by the glandular ventral shields on the other thoracic segments, where calcium is mixed with an organic secretion to make a paste.

This may be the reason why the worm may settle and grow on brown seaweeds such as Fucus, but avoids giant kelp, Nereocystis.

[4] Coldwater reefs built up by S. vermicularis take many years to develop and provide a hard substrate which other organisms use.

The reefs around the United Kingdom support a diverse community of sessile invertebrates, including sponges, hydroids, ascidians, bryozoans, the worm Pomatoceros triqueter, the sea anemone Metridium senile and bivalves such as Chlamys spp., Modiolus modiolus and queen scallop, Aequipecten opercularis.

Macrofauna include crabs such as Cancer pagurus, the sea urchins Echinus esculentus and Psammechinus miliaris, the brittle star Ophiothrix fragilis, the starfish Asterias rubens and the whelk Buccinum undatum.

[4] Predators of the worm include sea urchins, starfish, and the wrasses Crenilabrus melops and Ctenolabrus rupestris.