Note: original notes have been revised based on further information.

On limestone in mixed forest, on side of ravine. Associated with Caloplaca sp. and Lecidea sp. Thallus C-. Sections through immersed perithecia show round algal cells and hyaline muriform spores. Spores averaged 20 × 12 um (n=24) and a range of 15-25 × 9-15. Although around 6 or 7 perithecia total were examined, all spores fit this description; none were brown. No asci were seen, but one clump of about 8 spores was observed which could have come from an ascus.

The specimen is parasitized by a lichenicolous apothecial parasite, presumed to be Opegrapha pulvinata. See Observation 316951.


Studio shot
Photographed in field.
Photographed in field.
At 1000x oil immersion.
Taken with a Leuchtturm digital microscope camera.

Proposed Names

52% (1)
Recognized by sight
52% (1)
Based on microscopic features: Algae in perithecia, muriform spores.
78% (1)
Based on microscopic features: Large hyaline, muriform spores, about 20 × 12 um

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= Observer’s choice
= Current consensus


Add Comment
By: Dr. Gary Coté (gcote)
2018-06-19 06:02:41 PDT (-0700)

Hi Jason,
Glad you got a chance to view my Observation and that you agree with the ID. I sectioned and/or squashed a fair number of perithecia but the only muriform spores I found were hyaline. Those were abundant. The only brown spores were not muriform and appeared to associate with the parasite. S. clopimoides would thus be unlikely.

Great observation
By: Jason Hollinger (jason)
2018-06-13 10:06:08 PDT (-0700)

We don’t see this species very often (although it may not be as rare as the lack of observations would indicate). Striking how similar it looks to Staurothele clopimoides. Except for the smaller, hyaline (and presumably more numerous) spores, and the determinate margin.

Great ID!
By: J-Dar
2018-05-30 19:26:14 PDT (-0700)

Thanks for following through on this ID, it’s an interesting species, having those hyaline muriform spores. And as is always maddeningly frustrating but simultaneously fascinating with rock crusts is the parasitic organisms that make us think seven times about what we are seeing. Whenever I get stuck in the keys now I go back and make sure the ascomata I’m evaluating actually go with the thallus that I think it does! I’ve often been wrong…

By: Dr. Gary Coté (gcote)
2018-05-30 10:18:13 PDT (-0700)

Much thanks J-Dar for your comments that helped me figure out this species. I’m pretty new at identifying crustose species.

Your educated guess is probably good
By: J-Dar
2018-05-23 11:49:57 PDT (-0700)

I don’t have any experience with species out there but hyaline spores is a good start for Willeya diffractella.

I agree Staurothele, but which?
By: Dr. Gary Coté (gcote)
2018-05-23 08:08:23 PDT (-0700)

I agree with you that this is probably a Staurothele. But which? S. diffractella (Willeya diffractella) seems likely, except it is rather darker, and has 8-spored asci. But the species is reported in our area, likes shaded limestone, and has colorless muriform spores in the right size range. Need to find young asci with immature spores.

Your suggested S. fissa is ruled out by being much more verrucose, and living semi-aquatically on siliceous rock (and not being reported from around here).

S. monica, S. areolata and S. drummondii all have much larger brown spores arguing that I need to find more mature spores, if it’s one of them. Back to the cutting board!

Those structures should be immature muriform spores
By: J-Dar
2018-05-22 11:20:01 PDT (-0700)

I’m not sure what goes on with asci development in Staurothele, but my notes in observation 239956 are similar in that no asci were observed. For western species it didn’t matter too much, but I think you may need to determine number of spores per asci, unless there are other characters that can help you key it out.

Possible, but are those spores or asci?
By: Dr. Gary Coté (gcote)
2018-05-22 11:07:16 PDT (-0700)

I’m not familiar with Staurothele, so I will do some research on that. You are assuming that the spores are what is shown in the lower picture, which I thought were asci. No evidence of asci containing muriform spores. The ascomatal tissue did contain what appear to be algal cells — very small — see picture.

By: J-Dar
2018-05-22 10:51:03 PDT (-0700)

Spores are muriform, ascomata are perethecioid. Thallus a rimose brown crust.

Created: 2018-05-22 09:17:09 PDT (-0700)
Last modified: 2018-06-19 06:02:43 PDT (-0700)
Viewed: 100 times, last viewed: 2019-07-30 05:16:45 PDT (-0700)
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