These pictures show encrusting marine organisms that have attached to the red plastic part of a lobster pot. There is quite a variety. Most of the white elongated tubes are made by a marine worm Spirobranchus triqueter (previously called Pomatoceros triqueter) but there are a couple of coiled tubes which may be Hydroides norvegica. The other small lace-like structures are sea mats or Bryozoa, at least three species, one of which I have never seen before. I am not at all confident with naming Bryozoans. A good series of professional guides for identifying Bryozoa is produced by the Field Studies Council in their Synopses of British Fauna Series; and a good chapter is included in the Handbook of Marine Fauna of North-West Europe by P. J. Hayward and J. S. Ryland (Oxford University Press, 2nd Edition, 2017, Chapter 11, 603 – 637).

6 Replies to “Worm Tubes & Bryozoa”

  1. Going to be rather dim here, Jessica, but what exactly are these tubes? Exoskeletons? Some kind of cast? I’ve seen them but never given this detail a thought until now… RH

  2. HI, RH. The tubes are secreted (constructed) by the worm for protection. Different species of marine worms make calcareous tubes of different designs – some are spiral – all attached to hard objects like rock, shell, man-made objects that have become flotsam, and even seaweed. There is an earlier post giving some detail about the common type of chalky tube (Spirobranchus/Pomatoceros triqueter or “German writing”) shown in this post – although I do not know the exact mechanism by which they make the tubes. Other species of marine worms make tubes of small shell fragments or sand grains cemented together to line their burrows and these are usually found in colonies on sandy beaches at low tide level. In finer or muddier beach sediments some worm species make tubes entirely of mucous to prevent the sides of their burrow collapsing. Lastly there are the marine worms that live in mud and mucus tubes in small crevices on shells and soft rocks; the worms’ acid metabolic waste products dissolve the substrate in such a way that grooves are etched into the shell or rock to quite a depth, and usually in a U-shape, so that the front and back ends of the worm are at the surface of the object for feeding and excreting.

  3. Many thanks for the excellent explanation. Perfect sense. There’s a worm species on Abaco that produces amazing brown coiled / curly protective tubes – I didn’t make the link with your white ones.

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