When: 2014-03-30

Collection location: Papôa, Peniche, Portugal [Click for map]

Who: zaca

No specimen available

Another pleasant surprise from the same place of several others the same day. This time it seems clearly an Opegrapha sp., due to the pratically inexistent thallus and the form of apothecia – slit-like with acute ends – well visible to the naked eye. Some other features of this specimen include:
- Growing over a piece of calcareous rock;
- Thallus ver thin only noticeable with magnification (see the attached close up), cream-greyish coloured with some thin pruina;
- Apothecia slit-like up to 1.3 mm long, scattered, sessile, furrowed;
- Hymenium light coloured; epithecium and hypothecium brown, the latter a bit darker than the former;
- Asci long clavate with a small apical beak disposed among branched and anastomosing paraphyses;
- Ascospores first hialine, then brownish and finally becoming dark-brown, 5-septate with middle cells more enlarged, presenting a perispore when young, with the following average dimensions: Me = 26.5 × 8.6 um ; Qe = 3.1 (N=28); Most of the ascospores were mature or over-mature in the apothecia analyzed;
- All chemical reactions negative.
Using the key available for the genus in the British Flora (Ref. 1) I conclude that this must be Opegrapha mougeotti. In the description one can see that the number of septa may vary from 5 to 7(-8). I also saw in Ref. 2 a specimen with 7-septate spores according to the photo of the microscopy shown there. After some search on the web I see that this species has at least 3 varieties – var. meugeotti, var. garganica and var. lutescens – but I was not able to found the differences between them.


Close up:
Microscopy 1: Apothecial sections;
Microscopy 2: Inside the hymenium – A – Hypothecium; B – Epithecium; C – Exciple;
Microscopy 3: Asci,
Mycroscopy 4: Spores and algal cells (Trentepohlia).

Proposed Names

87% (1)
Used references: Ref. 1 (British Flora): Smith et al. (Editors), The Lichens of Great Britain and Ireland, British Lichen Society, 2nd edition, 2009; Ref. 2: Irish Lichens – http://www.irishlichens.ie/index.html.
Based on microscopic features
Based on chemical features

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= Observer’s choice
= Current consensus


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