Pyrenomycetes Species Page

Acanthostigma septoconstrictum

small separate ascomata
phragmospore
Acanthostigma septoconstrictum Promputtha & A.N. Mill.

Dothideomycetes
Tubeufiaceae
Figure from ANM536.1 (ILLS 59356, HOLOTYPE) Type Specimen: ILLS 59356 (ANM536.1)
Genbank Accession: GQ856143 (ITS), GQ850491 (LSU)
Complete Description
Ascomata superficial, scattered or gregarious, globose to subglobose, 200–250 µm diam, 150–200 µm high, shiny black when dry, densely setose, non-collapsing. Setae 1-celled, thick-walled, brown to dark brown, straight to slightly curved, with acute tip, 45–120 µm long, 5–7 µm wide in the middle. Ascomatal wall two-layered in longitudinal section, inner layer composed of 4–6 rows of brown, thin-walled, flattened to angular cells, outer layer composed of 1–2 rows of dark brown, angular to elongated cells which sometimes produce setae. Pseudoparaphyses numerous among asci, hyaline, up to 4.5 µm wide. Asci bitunicate, cylindrical-clavate to clavate, broadly rounded and thickened at the apex, short stipitate, 8-spored, 110–140 × 17–22 µm [126 × 20 ?m, n = 10]. Ascospores fusiform, straight or curved, ends asymmetrical, tapering at both ends with basal end more narrow than apical end, 2–3 inner cells near the apical end slightly broader than the others, 7–10 septate, constricted at the septa, hyaline, 40–50 × 5–6.5 µm [45.5 × 5.5 ?m, n = 20].
Occurrence
Scattered to gregarious on decorticated wood in mixed coniferous-deciduous forest. This species is only known from the type specimen.
Similar Taxa Comments
Acanthostigma septoconstrictum is most similar to A. ellisii Sacc. & Syd., but differs in having wider setae, larger asci and broader ascospores that are constricted at the septa.
Reference
Promputtha & Miller 2009, Mycologia 102(3): 574–587.