A bristleworm (Branchiomma bombyx)

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



Branchiomma bombyx is a yellowish-brown, cylindrical, segmented bristleworm that is up to 5 cm in length. The head has two palps, a small prostomium and compound eyes. The head bears a crown of up to 50 stiff, feather-like tentacles (radioles) marked by brown and violet bands with scattered eyespots which lie in between the palps and is divided into two sets. The body is divided into two sections, the first eight segments are thoracic, the remainder, approximately 70, are abdominal. Each segment has paired, epithelial, shoe-horn shaped, lobed flaps on either side, though towards the ends of the body they may have scalloped edges. The first thoracic segment lacks chaetae and forms a short collar that is marked by a ventral cleft that covers the base of the crown. The ventral chaetae of the thorax are small, short and hook-shaped, whereas the dorsal chaetae are slender. The abdominal chaetae are arranged in a C-shape.

Recorded distribution in Britain and Ireland

Branchiomma bombyx is widespread around all coasts of the British Isles but is not often found in great numbers.

Global distribution

Branchiomma bombyx is also found in the Mediterranean.


Branchiomma bombyx inhabits low water and sublittoral zones and is found amongst rock crevices, stones and shells.

Depth range


Identifying features

  • Yellowish-brown, segmented bristle-worm up to 5 cm in length.
  • Crown of up to 50 stiff, featherlike, violet and brown tentacles in two sets.
  • Short, ventrally notched collar on first segment.
  • Segments bear paired, shoe-horn shaped, epithelial flaps on each side.
  • Second to seventh segments are thoracic with short, hooked, ventral chaetae and longer, slender dorsal chaetae on each side.
  • Chaetae of abdominal segments arranged in a 'C' shape.

Additional information

Branchiomma bombyx forms tubes that it inhabits. This species may be mistaken for Megalomma spp. that have identical thoracic chaetae or, Bispira volutacornis with similar abdominal chaetae.

Listed by

- none -


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  1. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset https://www.nmni.com/CEDaR/CEDaR-Centre-for-Environmental-Data-and-Recording.aspx accessed via NBNAtlas.org on 2018-09-25.

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

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

  4. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-06-16


This review can be cited as:

Richards, S. 2007. Branchiomma bombyx 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 16-06-2024]. Available from: https://www.marlin.ac.uk/species/detail/18

Last Updated: 12/09/2007