Not the most convincing example, if it's an example at all, but could the pits seen here be the perithecia of this lichen?
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Some fungi are very poisonous so a mistaken ID could have serious consequences.
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I think you must have posted the wrong photo, these are acorn baranacles
... for the ID on the barnacles, about which I am clueless, but it's the potential lichen (Collemopsidium foveolatum) on the barnacles that I intended to be the focus here.
Edit:... but while we're at it: the small grey barnacles and the larger buff ones are the same species, but at different stages of development?
Sorry it's my ignorance of lichens, I hadn't known that they could grow where they could be immersed in the sea. Always something new to learn.
Yes the small grey ones are the juveniles, and I can't be certain but I think the species of barnacle is Chthamalus montagui.
As you said - always something new to learn.
Just seen the conversation after posting my ID - 'Fraid I can't see any lichens on my screen...
I googled the name then relooked at the photo at max magnification & you can see the pits on the buff barnacles,some seem empty some with green & afew near the bottom with blackish dots
Hmm, it might have been a good idea to be more detailed with the original notes, but yes, this is indeed Collemopsidium foveolatum. Interestingly, it is not only on the barnacles, but a few perithecia can also be seen set into the limpet shell that the barnacles have colonised.
Books don't specify which barnacle species host the lichen but personally I have only ever seen it on Chthamalus montagui. Yet it also occurs on limpet shells and on chalk and limestone rock. I suspect that it is not the species of barnacle that is actually important, but its position in barnacle zonation on a typical rocky shore.
More details and my own photo at http://www.lichens.lastdragon.org/Collemopsidium_foveolatum.html
It still appears in marine biology textbooks under its older and incorrect name, Pyrenocollema halodytes.
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