Collection location: Peniche, Portugal [Click for map]
Continuing my series of rare lichens, this time I report my first Thelopsis. It was growing on the a palm tree, in the empty space left by the fall of old leaves. The thallus is inconspicuous and it is only noticeable by the intense shine of the exposed parts of perithecia, similar to what one can observe with some stalked myxogastria like Physarum when the daylight follows on it. Such shine seem to be originated by the pruina (?) that covers the verrucas or perithecia-like fruits. Here are some of its microscopic features:
- Very big asci with very many (hundreds?) of spores;
- Spores hialine 0/1-septate;
- Hymenium hialine;
- Ascoma wall light brown, prosoplectenchymatous consisting of several rows of periclinally arranged hyphae;
- Algal layer of a green alga, whose cells are either green or orange-brown in color.
Step 1 – Delimitation of possible genera:
Since it is clearly a pyrenocarpus lichen with spores arranged in asci, each one with dozens or hundreds of spores, only a limited number of genera is possible, namely the following: Epigloea, Thelocarpon and Thelopsis. This can be achieved using Key 3 of British Flora (Ref. 1).
The first one of them can be immediately excluded, since the species in this genus are associated with free algae and are gelatinous. So, we are left with two genera.
Step 2 – Look for the alga:
It is known that the lichenized species in Thelocarpon have a Chlorococcace alga as photobiont whereas those in Thelopsis have Trentepohlia as photobiont. It happens that recently I´ve been envolved in the identification of many species in the genus Arthonia, which also has Trentepohlia as photobiont (to be considered in future observations). Thus, I´m pretty sure that the alga associated with this specimen is belongs to the genus Trentepohlia (see the corresponding photo attached).
Step 3 – Which Thelopsis sp.?
To go further it is necessary to give some more detailed information from microscopy:
- Average dimension of the spores: Me = 14.7 × 5.6 um ; Qe = 2.6 (N=21);
- Average dimensions of the algal cells: Me = 14.7 × 5.6 um ; Qe = 2.6 (N=10).
Looking for the species mentioned in Ref. 1, only one has 1-septate spores: T. isiaca, for which are not given the dimensions of the spores. However, it is mentioned there that this species grows on rock, though it is also mentioned there that the description given for it is based on extra-British material.
I decided to get further information and found Ref. 2, which introduces a new species of Thelopsis found in Spain at the time, T. foveolata. In that paper it is written and I quote:
“The only known European species with uniseptate spores is T. isiaca Stizenb., but this is a mainly epiphytic species that only sporadically grows on rocks.”.
It is also represented there a picture of the spores of T. foveolata, which are very similar to what I observed. The difference is that that species has an endolithic thallus and smaller spores: (6–)7–11(–13) x (3–)4–5 um. In addition a table is presented where the dimensions of the spores of T. isisaca are given: 12–15 x 5–8 um.
Thus I think to have found a name for my specimen: Thelopsis isiaca.
Let me also mention that all the photos from microscopy where obtained using the software Combine ZP, by Alan Hadley.
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Someone else asked me a few months ago why I don’t use CombineZP on compound microscope images. It’s just doesn’t look like it would be possible! But I keep telling myself I’ll try someday anyway, just to see what happens. Now I’ve definitely got to try it. Thanks for mentioning it!
re; Thelopsis — Sorry, I really wouldn’t know. Just as you say, there are very few peritheciate genera with polysporous asci. Your algae look like they have golden oil drops, so I agree they must be Trentepohlia. I’ve never seen anything from that genus, myself. (I’ve seen a couple lichenicolous specimens with polysporous perithecia, but that doesn’t count!)
Let me say that part of this belongs to you, since you always gave me good advises and explained the techiques whenever I was in doubt. I´m very grateful for you continued support.
That said, I was incredulous with your question about Combine ZP. I thought I was using it how you mentioned before. It doesn´t matter if it is a dissecting or a compound scope, we just get photos with a slightly diferent depth of field. I started to use it right now and I still don´t know all the possible tricks and I was lazy to read the explanations contained in the program.
How about Thelopsis? Did you collect any recently? The name I got for mine seems plausible to you?
You’re full of surprises today!
I was additionally surprised that you use CombineZP for your micrographs. I use this software regularly to achieve greater depth of field for photos through my dissecting stereoscope. But I’ve never worked out how it could be used to improve photos through a compound microscope. Would you mind sharing your secrets? Do you take multiple photos, focusing a tiny bit between each photo? Does that actually work??? (I confess I’ve never tried, it always seemed so implausible…)
Created: 2014-05-06 18:21:21 CDT (-0400)
Last modified: 2014-05-06 18:26:24 CDT (-0400)
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