It was glued to the remains of the warty tunicate's kelp holdfast, where it certainly hadn't been evident before. And the whole contraption, tunicate, holdfast, and tubeworm, had rolled up against the glass where I could see that it was alive and feeding.
|Red-trumpet calcareous tubeworm, Serpula columbiana|
These tubeworms secrete a mucus which precipitates calcium carbonate from seawater, which forms a hard tube, growing from the mouth end. (The calcium carbonate comes from dissolved shells of dead snails and other shelled creatures. Everything is used, reused, recycled.)
They settle on any hard surface. Seaweeds such as kelp aren't solid enough, but the holdfasts are as tough as wood, even when they're old and eroded, such as this one.
|Delicate colours. These tubeworms come in colours from pink and white to brilliant red.|
Each tubeworm has a lid, or operculum, which it pulls in after itself to plug the tube when it retreats. Open, it takes the shape of a funnel, or trumpet, which gives the tubeworm its name. In these photos, it can be seen, fuzzily, at the back, looking sort of like a pinkish badminton birdie.
|Backing off to see the whole tube in context.|
I'll have to take another batch of photos, to see if I can manage to focus on that operculum.