Xanthoria

[Chris Johnson]

The last of the pebbles. Collected from the upper and middle tidal zones, growing with Hydropunctaria maura. On first sight I thought Caloplaca with its scant thallus, but the spores said otherwise. On closer examination it became clear that the thallus had been serious erroded by the lichenicolous fungus Monodictys fuliginosa (many would say of rather more interest than the Xanthoria ).

Spore sizes: 13.3-15.4 x 5.4-6.8 µm

I doubt there’s enough here to take much further but posted for interest.

Chris

[Mark Powell]

I think those ascospores are fine for Caloplaca. They are septate, with a broad septum. If you are looking at images in books, bear in mind that the published images will be of ‘cleared’ spores. Your micrograph shows spores that appear to be fresh and mounted in water and hence the cell contents partially obscure what we consider to be the ‘proper’ cleared structure. Mounting in K or N should make the spores look like those in the books. If you don’t like using reagents on microscope slides, you can try heating the slide until nearly boiling. Otherwise you will have to wait a few weeks or months for the cell contents to dry up in storage (in herbarium material the spores are always ‘cleared’ by this drying out.

I think your orange-yellow lichen could be Caloplaca marina. Unfortunately that is not confirmed determination (I am a land-lubber and don’t pretend to do maritime lichens on sight).

The Monodictys is still the most interesting thing to me – I have never found it.

Mark

[Paul Cannon]

I think Mark is right about Caloplaca (now Flavoplaca) marina. There is a very similar image on the FGBI site (which is misbehaving yet again) from the Isle of Muck. And the images are beautiful, though spores mounted in KOH are more useful for ID in this group as that’s how the taxonomists have historically treated them (though they don’t always say).

[JennyS]

Thanks for another post Chris!

I managed to access the FGBI link for Monodictys fuliginosa but as the hosts are given as Lobaria pulmonaria and Xanthoria parietina is the lichenicolous fungus something else as your specimen is a Caloplaca?

[Paul Cannon]

I think Mark is right about Caloplaca (now Flavoplaca) marina. There is a very similar image on the FGBI site (which is misbehaving yet again) from the Isle of Muck. Looking back at the various images I have of this species, most of them have a black encrustation. Attached are three from Caloplaca marina from Galloway, which show what seems to be your Monodictys also. The species appears to be common all down the west coast (I have images from the Scilly Isles too). I think it is overgrowing and not necessarily a direct parasite, it also affects Caloplaca thallincola, unidentifiable maritime Lecanora species, Xanthoria parietina and even “rock”.

In the past this would have been dismissed as cyanobacterial crud, and I guess this remains a possibility – I’m not at all well up in this area. I think that Sue Knight has recently joined the forum, perhaps she would like to comment. The Monodictys images are here – http://fungi.myspecies.info/all-fungi/monodictys-fuliginosa

And your images are beautiful, though spores mounted in KOH are more useful for ID in this group as that’s how the taxonomists have historically treated them (though they don’t always say).

[Chris Johnson]

Mark Powell wrote:

I think those ascospores are fine for Caloplaca. They are septate, with a broad septum. If you are looking at images in books, bear in mind that the published images will be of ‘cleared’ spores. Your micrograph shows spores that appear to be fresh and mounted in water and hence the cell contents partially obscure what we consider to be the ‘proper’ cleared structure. Mounting in K or N should make the spores look like those in the books. If you don’t like using reagents on microscope slides, you can try heating the slide until nearly boiling. Otherwise you will have to wait a few weeks or months for the cell contents to dry up in storage (in herbarium material the spores are always ‘cleared’ by this drying out.

I think your orange-yellow lichen could be Caloplaca marina. Unfortunately that is not confirmed determination (I am a land-lubber and don’t pretend to do maritime lichens on sight).

The Monodictys is still the most interesting thing to me – I have never found it.

Mark

Many thanks for commenting, Mark.

I alway try for a spore-drop if enough material is available as I then know they are mature and will give correct measurements. I then mount in water as some reagents can distort the spores. If I am happy with the result, I don’t take it any further. However, I wasn’t aware how useful KOH was in this respect, so with do two set in future.

Chris

[Chris Johnson]

JennyS wrote:

Thanks for another post Chris!

I managed to access the FGBI link for Monodictys fuliginosa but as the hosts are given as Lobaria pulmonaria and Xanthoria parietina is the lichenicolous fungus something else as your specimen is a Caloplaca?

Hi Jenny

There is no doubt regarding Monodictys fuliginosa as I examined it carefully under the microscope. Paul has now clarified the situation.

Chris

[Chris Johnson]

Paul Cannon wrote:

I think Mark is right about Caloplaca (now Flavoplaca) marina. There is a very similar image on the FGBI site (which is misbehaving yet again) from the Isle of Muck. Looking back at the various images I have of this species, most of them have a black encrustation. Attached are three from Caloplaca marina from Galloway, which show what seems to be your Monodictys also. The species appears to be common all down the west coast (I have images from the Scilly Isles too). I think it is overgrowing and not necessarily a direct parasite, it also affects Caloplaca thallincola, unidentifiable maritime Lecanora species, Xanthoria parietina and even “rock”.

In the past this would have been dismissed as cyanobacterial crud, and I guess this remains a possibility – I’m not at all well up in this area. I think that Sue Knight has recently joined the forum, perhaps she would like to comment. The Monodictys images are here – http://fungi.myspecies.info/all-fungi/monodictys-fuliginosa

And your images are beautiful, though spores mounted in KOH are more useful for ID in this group as that’s how the taxonomists have historically treated them (though they don’t always say).

Paul

Thanks for the support of Flavoplaca marina and the insight into Monodictys fuliginosa‘s hosts.

I’m keen to get as many spore-drops as possible as I find Smith et al., Dobson and others all quote the same sizes which suggest being cribbed from a common source, and possibly from the asci or squashes, as mine are often at variance.

Chris

[Mark Powell]

This has been a fascinating subject for me so I am glad that you posted about your ‘last pebble’.

I don’t know any lichenologists who do spore drops but we might get better results if we did… I have ever known lichenologists to measure spores in squash preparations, measuring the ones released from the ascus. This of course does introduce a variable because some people might be more aggressive in their squashing than others and so end up with a greater proportion of immature spores from asci that weren’t really ‘ready’ to give up their contents.

The Monodictys is interesting too. I might have overlooked it as cyanobacterial. One would think that separating eukaryote cells from prokaryote ones ought to be easy since they are so distantly related but I suspect that it is not easy to distinguish them using ordinary light microscopy?

I often find what I take to be cyanobacteria on Xanthoria parietina:

[Chris Johnson]

Not sure what you have there, Mark, but it doesn’t look right for Monodictys fuliginosa. The conidia are quite variable in size but do have a set form and are dark brown.

This is my ten-penneth: http://www.outerhebridesfungi.co.uk/species.php?id=448

Chris

[Chris Johnson]

Mark

I’ve finished with this sample if you would like it for the Monodictys fuliginosa?

Chris

[Mark Powell]

Hi Chris,

That’s a really kind offer. You wouldn’t necessarily need to send the whole pebble. You could just scrape a bit of the ‘infected’ Caloplaca off into a packet if that makes it easier/cheaper for you. It would interest me to compare the Monodictys microscopically with cyanobacterial cells from similar black gunge.

If you don’t have my address, one way of contacting me is via the Garden Survey section of the BLS website:

http://www.britishlichensociety.org.uk/activities/garden-survey

Many thanks,

Mark

[Chris Johnson]

Mark

It’s no longer a pebble – I use a diamond disk-cutter to make them more user-friendly.

Can’t see your address on that site, are you suggesting I send to:

The British Lichen Society, c/o Lichen Herbarium, Dept of Life Sciences, Natural History Museum, LONDON SW7 5BD?

If not, you could send me a PM.

Chris

[SueK]

The dark spherical cells on Chris’s photos in the Xanthoria post look like cyanobacteria to me, but then I’m not familiar with any fungi that might have a similar appearance. SueK

[Chris Johnson]

Welcome to the forum Sue, and thank you for commenting on the thread.

I wonder if you meant Mark’s photos?

Chris

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