synan's picture

Freshwater lichen headache #1

Observed: 6th July 2012 By: synansynan is knowledgeable about Fungi and Lichenssynan’s earned reputation in Fungi and Lichenssynan’s earned reputation in Fungi and Lichenssynan’s earned reputation in Fungi and Lichenssynan’s earned reputation in Fungi and Lichenssynan’s earned reputation in Fungi and Lichens
Trapelia coarctata (2)
Trapelia coarctata (3)
Trapelia coarctata (4)
Trapelia coarctata (5)

Near disused lead mine on siliceous rock in splash zone within stream. Probably regularly immersed. Thallus crustose, green (both wet and dry), C+ red (fleeting), K-; apothecia lecanorine, red-brown, approx. 0.3-0.4mm at maturity, margin becoming excluded; photobiont chlorococcoid; asci 8-spored; ascospores simple, ellipsoid to ovoid, colourless, mostly with a single large oil globule, c. 17-20 x 9-10μm in water; paraphyses branched and anastomosing.


Caution: Do NOT use iSpot to identify fungi to eat!

Some fungi are very poisonous so a mistaken ID could have serious consequences.

Species interactions

No interactions present.


synan's picture

Thanks Phil

I don't know I. lacustris, but its paraphyses are supposed to be unbranched and its apothecia are immersed, so I'm a bit doubtful. The paraphyses in my find are branched and the apothecia are sessile. It seems I. lacustris can be cream-white in the shade, but I don't know about green.

Good suggestion - a lot of other characters match, including the spores.

Edit: I see there is a bit of confusion about the photobiont in Dobson (2011), where it is wrongly given as Trentepohlia.


synan's picture

Trapelia coarctata

I have somehow arrived at this and then returned to check the C-reaction, which is indeed C+ red, but so mild and fleeting that I completely missed it at first.

Sorry for the dud information!


pf339's picture


I have now seen lots of probable examples in Ceredigion of Ionaspis lacustris (e.g and realise that your Trapelia coarctata is nothing like Ionaspis lacustris!
All helping me in trying to find out a bit more about lichens!

synan's picture


Hi Phil

I think we have both learnt a lot in the 2 years since I posted this. I now know I. lacustris better too and have seen plenty of it in Snowdonia this month. I really should look at this specimen again to see if I can be more certain about it.

I edited this observation to change its habitat to freshwater, which is why it must have flagged up in your changes. I was experimenting with iSpot's new projects to see if I could isolate freshwater lichens (not that there are many of those on iSpot!), but it doesn't seem to work.