A bristleworm (Janua heterostropha)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



The Spirorbidae, with their tightly coiled white tubes of calcium carbonate, are unmistakable. Janua heterostropha is one of the smaller spirorbids and is found on a variety of hard substrata and algae on rocky shores. The calcareous tube is coiled with the opening facing anti-clockwise (dextral), the coil having a diameter of up to 2 mm. Tube with three longitudinal ridges which may be lost by scour in larger individuals. There are two colour morphs of the adult. Bright orange adults occur in shallow water while pale coloured adults occur in deeper water. When the branchial crown of tentacles is everted, the brood chamber is obvious. Early embryos are brown/black but become pale later on with red eyespots.

Recorded distribution in Britain and Ireland

Recorded from a few locations in Britain but is probably under recorded and common on all rocky shores.

Global distribution

Considered to be the most common spirorbid in the world, especially in Britain, extending from the Arctic Circle to the tropics.


Occurs on stones, shells and algae from high water of neap tides to depths of 120 m. In the intertidal it can be found from sheltered to wave exposed shores, which it survives by inhabiting crevices.

Depth range


Identifying features

  • Tube is coiled with the opening facing anti-clockwise (dextral).
  • Coil diameter up to 2 mm.
  • Tube with three longitudinal ridges (which may be lost by scour in larger individuals).
  • Embryos are brooded in a brood chamber attached to the operculum.

Additional information

No text entered

Listed by

- none -


  1. Bruce, J.R., Colman, J.S. & Jones, N.S., 1963. Marine fauna of the Isle of Man. Liverpool: Liverpool University Press.

  2. Crothers, J.H. (ed.), 1966. Dale Fort Marine Fauna. London: Field Studies Council.

  3. Foster-Smith, J. (ed.), 2000. The marine fauna and flora of the Cullercoats District. Marine species records for the North East Coast of England. Sunderland: Penshaw Press, for the Dove Marine Laboratory, University of Newcastle upon Tyne.

  4. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  5. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  6. Knight-Jones, P. & Knight-Jones, E.W., 1977. Taxonomy and ecology of British Spirorbidae (Polychaeta). Journal of the Marine Biological Association of the United Kingdom, 57, 453-499.


  1. Fenwick, 2018. Aphotomarine. Occurrence dataset http://www.aphotomarine.com/index.html Accessed via NBNAtlas.org on 2018-10-01

  2. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  3. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-07-21


This review can be cited as:

Neal, K.J. 2004. Janua heterostropha A bristleworm. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-07-2024]. Available from: https://marlin.ac.uk/species/detail/2037

Last Updated: 19/08/2004