Coil Worm

Appearance

They have a smooth, white, sinistral coiled shell encasing an orange body about 3 mm in length. The tube has a peripheral flange where it attaches to the substrate.

The worm has a short abdominal region and a slightly broader thorax terminating in ten stiff tentacles, used to filter food from the water. One of the tentacles is slightly larger than the rest and shaped like a saucer, which is used as an operculum. This seals the opening of the shell and serves to protect the worm from predators and desiccation when out of water.

Distribution

All around Britain and Ireland; North Norway to the English Channel. Cape Cod.

Habitat

It lives primarily on toothed wrack and bladder wrack, but is also found on the basal part of thongweed . Numerous individuals can be found on any one surface.

Reproduction

''Spirorbis spirorbis'' are cross fertilising hermaphrodites, who brood their young in a tube attached to the worm inside the shell. The larvae are released at an advanced stage of development and spend just a few hours as free-living organisms before attaching themselves to the nearest suitable surface, often the same seaweed as the parent.