Spirorbis worm

Spirorbis worm

Observation - Spirorbis worm - UK and Ireland. Description: The tiny 'shell' is commonly found on the dried surfaces of flat seaweed at the top of the tide line. Picture 1 also shows a desiccated colony of sea mat. Sometimes seen thriving below the low water mark but rarely observed sufficiently closely to see th

The tiny 'shell' is commonly found on the dried surfaces of flat seaweed at the top of the tide line. Picture 1 also shows a desiccated colony of sea mat.
Sometimes seen thriving below the low water mark but rarely observed sufficiently closely to see the animal they contain. Under my new microscope, the small (2-4 mm) coiled polychaete worm, which we almost never see, shows up to ten filter feeding tentacles. These briskly come and go as they are sensitive to movement and light changes.

There are a number of Spirorbis worms but these might be (almost certainly are) Spirorbis spirorbis, the shell being smooth, white, sinistral (coiled left-handed) and about the right size.
See http://www.seawater.no/fauna/annelida/spirorbis.html
Whilst watching and trying to observe detail, a carefree mollusc wanderered into the arena - I'd like to think that it is the edible winkle but it could be one of a number of grazing molluscs. In this case on serrated wrack (Fucus serratus)
Picture five with graticuile shows 0.05mm scale (makes the mollusc about 1.6mm across). The picture also shows (just) the operculum, which seals the opening of the shell and serves to protect the worm from predators. I noticed it was deployed the moment the snail touched the shell.
Core Edit - Added picture 6 and corrected the scale.
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