Collected at the Coastwise bioblitz. This purple mass is encircling the branches of Cladophora rupestris.
No interactions present.
I think this is more common than the Web would have you think. Why can't sponges be epiphytic on seaweed fronds and why is it not, apparently, normal?
See my post here - http://www.ispot.org.uk/node/366005 which shows, undoubtedly, a sponge using the frond as a home.
Whilst, like you, I couldn't find good evidence, it seems that mine could be Amphilectus fucorum and so could yours - just an immature colony perhaps.
Searching the Web under its old name Esperiopsis fucorum is much more 'fruitful' - get it?
Of course, I could agree to 'Sponge' but will wait (that's the way in Marines)
The bryozoan Alcyonidium hirsuitum appears on Page 254 of Collins Complete - worth considering - and see here http://www.ispot.org.uk/node/343947
(A.diaphanum - watch out for Doggerbank itch!)
So, over two weeks have passed and we still don't know if this is a sponge, (a primitive group near the front of H & R) or a bryozoan (near the back of the book). An unusual position to be in....
Aha yes Jo. What we need are better photos and a 'cooler' description of the structure. It's not like you to be so 'drab'.
...and now I see you are languishing in the Help with confirming Identification carousel. None of nine have made it there - so unfair!!
..quoted here http://www.ispot.org.uk/node/371917
Still pondering this one, I suddenly remembered Peter Hayward’s small book Animals on Seaweed (written on his own) and there, on cover, is a blue ascidscian. Which set me thinking… I had originally, when the specimen was fresh, dissected a bit under the high power microscope, but could see no sign of zooids and so gave up on the idea of an ascidian. However, in the ascidian key of this small book is “Didemnum candidum. Colony developing a flat, coarse-surfaced, bluish-grey or light purple incrusting kelp stipes. Individual zooids not readily recognisable". WoRMS has this as an ‘accepted’ species, but I have yet to see any recent records as a British species. However, Didemnum maculatum is British and H & R say of it ‘On rocks stones, Laminaria holdfasts, Cystoseira, Delesseria etc.” So, if we include C. rupestris in ‘etc’ we may have a result. What do ‘mariners’ think?
Hayward P. 2001. Animals on Seaweed. Richmond publishing.
The ascidian Didemnum (unlike the obvious ones we know) is worth following because (I think!) they seem sponge lookalikes; though yours no longer looks like a sponge to me.
Your link takes us to D.maculosum - I think you would remember if it was spotted - it doesn't appear to be.
Here http://en.wikipedia.org/wiki/Didemnum is a list (Wiki) but D.candidum and D.maculatum are missing and, in any case, only two links show enough detail for 'our' investigation.
I have seen squirts that could easily fit onto (colonise) seaweed fronds and, possibly, take on a form not normally seen.
There is a really interesting pic here http://en.wikipedia.org/wiki/File:Didemnum_overgrowing_dark_green_algae.jpg
and it makes me wonder whether I need to re-evaluate my recent post here http://www.ispot.org.uk/node/371917
One thing against you Jo., is the quality of your photo and the absence of REAL close ups.
If you want to increase your headache then check this - Eudistoma capsulatum - to find that it can and does colonise a flexible friend. Whilst it appears to be absent from UK waters, it might, via Google Images, give you ideas.
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