ITALIC 8.0

Placopyrenium pseudocinereoatrum Thüs & Nascimbene

in Nascimbene & al. , J. Fungi, 9, 380: 14, 2023 (as "pseudocineroatrum")

Synonyms:

Distribution: C - Sar (Nascimbene & al. 2023).

Description: Thallus crustose to subsquamulose, well-delimited, up to 0.46 mm thick, rimose-areolate, starting the development on the thalli of Circinaria ochracea, later becoming independent, the areoles angular, constricted at base, 0.5-1 mm wide, flat to slightly convex, the peripheral ones slightly elongated, pale grey to mid-brown with black sides, faintly to distinctly pruinose (due to the epinecral layer); young thalli thinner, at first visible as a brown-grey patch on the host. Cortex poorly differentiated, paraplectenchymatous, the cell walls often with a brown pigment, locally with a more or less developed, c. 10 μm thick epinecral layer of dead but not collapsed cells; photobiont layer c. 200 μm thick, the algal cells arranged in clusters; medulla white or, in lower parts of thallus, with a brownish pigment in parasitic forms, brown-black in independently growing specimens. Perithecia immersed, globose, the apex often visible as a small brown dot. Involucrellum absent; exciple dark black-brown in upper part, brown in lower part, up to 240 μm in diam.; hamathecium of periphyses and periphysoids measuring c. 30 x 2 μm, interascal filaments absent; hymenial gel hemiamyloid. Asci 8-spored, clavate, I-, fissitunicate, the wall thickened above with an indistinct ocular chamber, Verrucaria-type. Ascospores 1-celled, hyaline, ellipsoid, 11-21 x 6.5-9.5 μm, without a distinct perispore, occasionally of distinctly different sizes in the same perithecium. Pycnidia immersed, the tips slightly projecting over the thallus, the wall colourless in lower part, black near the ostiole, multilocular, Dermatocarpon-type. Conidia simple, hyaline, bacilliform, straight or slightly curved, 4-7 x c. 1 μm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.

Note: a recently-described species growing in the splash zone of Mediterranean creeks which are sometimes dry in summer, starting the life-cycle on Circinaria ochracea. It is similar to P. cinereoatratum (Degel.) Orange, differing in the (on average) slightly shorter ascospores, the different host, and different ITS sequences. Hitherto known only from Sardinia

Growth form: Crustose

Substrata: rocks

Photobiont: green algae other than Trentepohlia

Reproductive strategy: mainly sexual

Periodically submerged (e.g. in creeks)

paras Circinaria ochracea

Commonnes-rarity: (info)

Alpine belt: absent

Subalpine belt: absent

Oromediterranean belt: absent

Montane belt: rare

Submediterranean belt: absent

Padanian area: absent

Humid submediterranean belt: absent

Humid mediterranean belt: absent

Dry mediterranean belt: absent

pH of the substrata:

1

2

3

4

5

(info)

Solar irradiation:

1

2

3

4

5

(info)

Aridity:

1

2

3

4

5

(info)

Eutrophication:

1

2

3

4

5

(info)

Poleotolerance:

0

1

2

3

(info)

Altitudinal distribution:

1

2

3

4

5

6

(info)

Predictive model

Source: Nascimbene & al. 2023

Italy, Sardinia
(A) Holotype of Placopyrenium pseudocinereoatrum with young perithecia (=SMNS-STU-F- 0002927) on Circinaria ochracea (=SMNS-STU-F0002797). (B) Isotype specimen with sectioned mature perithecia, SMNS-STU-F-0002808. (C) Section with young perithecium in subsquamulose Thallus part. (D) Thallus section with pseudocortex and photobiont layer from the holotype. (D) Scale bars in (A) = 5 mm, in (B) = 1 mm, (C) = 0.2 mm, (D) = 0.02 mm.