Observation 364262: Acarospora A. Massal.

Notes:
On shale cobble in a semi-arid annual grassland habitat.

Thallus consists of chocolate brown bullate areoles tightly arranged, nearly always with a depression in the center of the areoles that collects dust or a crusty pruina. Cortex C-. All parts POL-. Apothecia originating immersed, 1(3) per areole, without an elevated parathecial crown, with thalline margin, with red-brown disk, emerging to completely envelop the areole and appear sessile with a nearly black disk and rims lacking algae. Algae across the base of the apothecia is thick but becomes sparse. Epihymenium reddish. Hymenium hyaline. Exciple with a hyaline space between cortex and algae, always continuing over the algae into the hymenium. Paraphyses simple, filiform, with oil drops, segmented, slightly enlarged near tip to <2µm. Asci with many tiny spores. Pycnida not observed, but needs further inspection.

Spores many per ascus, small, 4-6×2µm.

This is an interesting Acarospora that shows development of pseudolecanorine-like apothecia. It is similar in micro features to the newly described Acarospora erratica, but that one occurs on calcareous rock. Knudsen didn’t recognize this one from photo. It will be sent to him in Prague for sequencing.

Images

Developing apothecia
100x in C
100x in C
Detail of exciple at 400x
Detail of exciple at 400x
Paraphyses
Asci and paraphyses
Spores

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