A scale worm (Malmgrenia lunulata)

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



The body is 10-35 mm long, broad, flattened and more or less straight-sided. The frontal parapodia are not well marked. The dorsal parapodia extend only as far as the chaetae. It has 15 pairs of oval scales that overlap and cover the back except for the last two segments. The dorsal scales are smooth and unfringed and decorated with very variable patterns. The scales are pale reddish brown in colour with a dark circle on each scale. The underside surface has a median dark-red band and transverse brownish stripes posterioirly. The head is reddish in colour with brown markings on the antennae and parapodia. This species displays bioluminescence.

Recorded distribution in Britain and Ireland

Common around Britain with isolated records in Northern Ireland.

Global distribution

Recorded from the western coasts of Europe to the Mediterranean.


This species is found at low water and under stones or in crevices. Has been found among holdfasts of kelp on the Breakwater in Plymouth Sound.

Depth range


Identifying features

  • The body is 10-35 mm long, broad and flattened.
  • Dorsal parapodia extended only as far as chaetae.
  • 15 pairs of overlapping, oval scales.
  • Pale reddish brown in colour.
  • A dark spot on each scale.
  • Bioluminescent.

Additional information

Often found living as a commensal with other worms, sea cucumbers and the brittlestar Amphiura brachiata. The pigmentation of the worm often perfectly mimics the hosts colouration.

Listed by

- none -


  1. Gibson, R., Hextall, B. & Rogers, A., 2001. Photographic guide to the sea and seashore life of Britain and north-west Europe. Oxford: Oxford University Press.

  2. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  3. 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.]

  4. Rouse, G.W. & Pleijel, F., 2001. Polychaetes. New York: Oxford University Press.


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

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-07-25


This review can be cited as:

Carter, M.C. 2003. Malmgrenia lunulata A scale worm. 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 25-07-2024]. Available from: https://www.marlin.ac.uk/species/detail/1952

Last Updated: 10/09/2003