Observation 165134: Arthonia stellaris Kremp.

When: 2014-03-28

Collection location: Sintra, Portugal [Click for map]

Who: zaca

No specimen available

Some features of this specimen:
- Growing on bark;
- Thallus light coloured (whitish-greenish) well delimited by a pale brown zone;
- Apothecia small linear to stellate, purplish brown, dispersed by the whole thallus;
- Chemical reactions negative;
- Asci rounded, very small (dimensions of 30-40 × 15-20 um);
- Spores septate, mostly with 3 or 4 septa, hialine when young becoming brown with age, with average dimensions: Me = 16.5 × 6.1 um ; Qe = 2.7 (N=26);
- Algal layer of Trentepohlia.


Chemical reactions;
Microscopy 1: Asci, Algal cels and paraphysoids;
Microscopy 2: Spores.

Proposed Names

58% (1)
Eye3 Eyes3
Used references: Smith et al. (Editors), The Lichens of Great Britain and Ireland, British Lichen Society, 2nd edition, 2009.
Based on microscopic features
Based on chemical features

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Arthonia is certainly a very philosophical entity
By: Jason Hollinger (jason)
2014-05-13 15:56:07 CDT (-0500)

Yes, I suppose you are right: I’m avoiding work, but trying my best to engage in lichens anyway. :)

I’ve always wondered about these lichens that produce abundant apothecia, but no spores. Your comment about Graphidaceae naturally reminded me. I can’t help asking the questions. Too bad I’m so bad at answering them! And how, indeed, does one go about answering this question: why would a species invest so many resources into producing something with no apparent value — either lots of apothecia which fail to produce spores, or lots of spores which fail to disperse? Where does one start to devise an experiment? What sorts of observations would help shed light on the question?

No need to respond. I’m just avoiding work!

PhIlosofical stage?
By: zaca
2014-05-13 15:41:54 CDT (-0500)

I understand from your words that you are passing to another stage: the philosophical one. Since you have no time to analyse the material of your observations, you are trying to find answers for questions that are to be posed by the humanity as a whole. I’m thinking about your question related to: Why are they (the spores) not ejected??
If you put a big lab working on this, certainly a (partial) answer to the question will appear after some time, because we have already scientific means to deal with that question or with related ones. But this requires money and political discernment , which are not so abundant.
Therefore, it is a question of each one of us to find its small piece of understanding. Let´s perform that step.

About our Collemataceae and Caloplaca and several others, I´m proud to have so abundant material. Unfortunately, it is not studied as it deserves and, as you know, I´m always “rediscovering” things that should be trivial for someone who really knows about the matter. But, that is life.
Thanks, Jason, for this exchange opinions and thoughts.

Thanks, Jason, for this exchange opinions and thoughts.

Too many specimens, too little time
By: Jason Hollinger (jason)
2014-05-13 14:45:26 CDT (-0500)

This is a very common problem, as it turns out, one which applies seemingly equally well to all nationalities! I salute you for taking the time to continue to post such fully-documented observations. I keep promising myself to post things some day. Perhaps automate the process, since I have all my notes on my computer and readily available. Maybe some day…

Well, congratulations on having such fertile Arthonia species. Yet another way in which Portugal lichens are superior to our scrawny, infertile lichens in North America. :) (I’m still jealous of your Collemataceae and Caloplaca!)

re: Graphidaceae — Yes, I find the same problem with many graphids, too. Spores are either hard to find or all shriveled up and post-mature. (Why are they not ejected?? What’s the point in producing all those complex spores, only to let them shrivel up and die in the ascus?? Bizarre. There’s got to be some factor in their reproductive process we’re missing. Maybe an animal vector or some other external condition which is required for spore dispersal. Sort of like how giant sequoias require fire in order to germinate.)

Arthonia spores are beautiful!
By: zaca
2014-05-13 13:37:21 CDT (-0500)

I cannot complain of the existence of many sterile specimens, in general, and certainly not in Arthonia, in particular. Sometimes what happens is that there are only few spores, or either only baby spores or extra-mature ones. This is particularly the case of species in Graphidaceae.
Presently my problem is that I have to many samples for the time I have to analyze them. In this past the problem was that I hadn´t a convenient scope, so that I avoided to collect specimens which were impossible to analyze.

Love those Arthonia spores
By: Jason Hollinger (jason)
2014-05-13 13:04:24 CDT (-0500)

You seem not to have any trouble finding spores in your material, either specimens on bark or on soil or rock. I frequently find sterile specimens in North America: apothecia are abundant, lack exciple, even asci are present and arthonioid (so you can guess the genus confidently), but no spores are to be found anywhere. This seems particularly common with the species which lack photobiont. Do you also find lots of specimens that refuse to give up spores? (Meaning, I guess, we’re just seeing a biased sample of your fertile specimens only on MO?)

Created: 2014-05-12 20:18:20 CDT (-0500)
Last modified: 2014-05-12 20:18:27 CDT (-0500)
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