Arthrinium descalsii Pintos & P. Alvarado sp. nov. Fig. 6

Etymology.

Named to honor the eminent mycologist Enric Descals Callisen.

Diagnosis.

Sexual morph: Stromata forming black fusiform spots that merge with each other with age, forming an erumpent black mass visible at the naked eye, 2-10 × 0.2-0.5 mm in size, with the long axis broken at the top revealing the ostioles of pseudothecia. Ascomata pseudothecia, subglobose with a flattened base, arranged in rows, brown to dark brown, 150-220 μm high × 150-250 μm wide (n = 20). Peridium with several layers of cells arranged in textura angularis, with a conspicuous ostiole 50-80 μm in diameter, periphysate. Hamathecium paraphyses hyphae-like, septate, hyaline. Asci cylindrical, clavate, with a short or indistinct pedicel, with rounded apices, measuring (73 –)82–95(– 111) × (16 –)17–20(– 23) μm (n = 30). Ascospores uniseriate to biseriate, hyaline, smooth-walled, apiosporic, composed of a large curved upper cell and smaller lower cell, fusiform to slightly curved in shape with narrowly rounded ends, guttulated, sometimes with a thick gelatinous sheath, (17 –)18–22(– 24) × (6 –)7–9(– 10) μm, and a basal cell 3-5 μm (n = 45). Asexual morph: Mycelium hyaline, septate, branched, hyphae 1.5-4.5 μm in diameter Conidiophores reduced to the conidiogenous cells. Conidiogenous cells solitary on hyphae, ampuliform, hyaline to brown, 5 × 4 μm . Conidia brown, smooth, guttulate, globose to ellipsoid (5 –)7(– 8) µm long (n = 20) in face view, lenticular with a paler equatorial slit and 6-7 μm long in side view (n = 10). Sterile cells elongated, sometimes mixed among conidia. Culture characteristics: ascospores germinating on MEA 2% within 24-48 h. Colonies flat, spreading, with sparse aerial mycelium, pale siena.

Notes.

Arthrinium descalsii is closely related with A. phragmitis and A. balearicum . It was found in the Mediterranean grass Ampelodesmos mauritanicus, although additional samples are needed before concluding if it could be exclusively associated with this endemic host. Ascospore size is often smaller than that of A. balearicum, (23 –)26–30(– 32) × (7 –)9–10(– 12) µm, but it matches that reported in the protologue of A. phragmitis, (20 –)22–24(– 25) × (7 –)8–9(– 10) µm . However, the conidiophores of A. descalsii are reduced to conidiogenous cells, while those of A. phragmitis measure about 10-45 × 1.5-2 µm, and conidia are slightly smaller in face view, measuring (5 –)7(– 8) µm long in A. descalsii and up to 8 –10(– 11) µm in A. phragmitis .

Type.

Spain: Balearic Islands: Mallorca, es Capdella, on dead stems of Ampelodesmos mauritanicus, 31 Jan. 2018, A. Pintos (MA-Fungi 91724 holotype, AP31118A isotype, CBS 145130 ex-type culture).