Pseudogymnoascus russus Childress & Quandt, 2025

Childress, Mary K., Dragone, Nicholas B., Young, Benjamin D., Adams, Byron J., Fierer, Noah & Quandt, C. Alisha, 2025, Three new Pseudogymnoascus species (Pseudeurotiaceae, Thelebolales) described from Antarctic soils, IMA Fungus 16, pp. e 142219-e 142219 : e142219-

Pseudogymnoascus russus Childress & Quandt sp. nov

Figs 7 , 8

Etymology.

The name refers to the russet red color of exudates produced by colonies on PDA at 15 ° C.

Type.

Antarctica • Shackleton Glacier, Mount Wasko , 84°33'34.5"S, 176°48'40.38"W, 321 m, from soil, 4 Jan 2018, coll. I. Hogg, D. Wall & M. Diaz. Holotype 99 ASP 01, stored in a metabolically inactive state in the CFMR Herbarium, while ex-type metabolically active material is stored in the Reference Culture Collection at the CFMR .

Description.

On CMA and PDA hyphae branched, septate, hyaline, smooth, 0.9–2.1 μm wide. Racquet hyphae absent. Fertile hyphae bearing aleurioconidia, sessile or stalked, rarely bearing intercalary conidia. Arthroconidia not observed. Conidiophores abundant, solitary, generally erect, sometimes curved, arising in acute angles with the main axis, hyaline, smooth, usually bearing verticils of two to four branches arising from the stipe at an acute angle. Conidiophores more abundant on CMA than PDA. Aleurioconidia are pyriform to clavate or obovoid with a broad truncate basal scar, 2.8–4.8 × 2.1–3.4 μm (av = 3.7 × 2.8 μm, n = 50), in conidiophores separated by connective cells. Intercalary conidia are rare, pyriform to clavate, or subglobose, 3.0–4.6 × 2.1–3.2 μm (av = 3.76 × 2.5 μm, n = 13), in conidiophores separated by connective cells. Ascomata absent.

Culture characteristics.

On OA, colonies reach 45 mm in diameter after 28 days at 15 ° C, round, appressed, colorless to white, consisting of immersed and hyaline hyphae, small clumps of white cottony aerial mycelium emerging throughout the colony, exudates and diffusible pigments absent; reverse white. On CMA, colonies reach 36 mm in diameter after 28 days at 15 ° C, round, flat, floccose, gray to white, margin filamentous and white, exudates and diffusible pigments absent; reverse rusty brown with white margin. On SDA, colonies reach 31 mm in diameter after 28 days at 15 ° C, irregular, raised, floccose, radial grooves, yellowish to gray, margin filamentous and white, exudates in the form of transparent and colorless droplets, diffusible pigments faint brown; reverse brown. On PDA, colonies reach 30 mm in diameter after 28 days at 15 ° C, irregular, slightly raised, umbonate, floccose, radial grooves, gray, margin filamentous and white, exudates in the form of large russet red droplets, diffusible pigments faint brown; reverse dark brown. Also on PDA, colonies reach 28 mm in diameter after 28 days at 25 ° C, slightly irregular / nearly round, raised, slightly umbonate, floccose aerial mycelium, light pink to gray to white, margin filamentous and white, exudates in the form of rust colored droplets, brown diffusible pigments; reverse dark brown. Conidial production was greater at 25 ° C compared to 15 ° C. Growth occurred at 5 ° C, 15 ° C, and 25 ° C; Growth rates were approximately equal at 15 ° C and 25 ° C. No culture attenuation was observed.

Distribution.

Mount Franke and Mount Wasko, Shackleton Glacier, Antarctica.

Ecology / substrate.

Cultured from Antarctic soil.

Additional specimen examined.

Shackleton Glacier, 390 ASP, ibid.

Genbank accession numbers.

ITS = PQ 453551, LSU = PQ 453556, MCM 7 = PQ 497090, RPB 2 = PQ 497095, TEF 1 = PQ 497099,

NCBI BioSample genome accession.

SAMN 40283452 .

Note.

Pseudogymnoascus russus has been placed as a member of clade B (Figs 1 , 2 ). Clade B is comprised of P. shaanxiensis , P. papyriferae , P. australis , and P. griseus ( Zhang et al. 2020, 2023 b; Villanueva et al. 2021) Clade B also includes unidentified species RMFC 101, 10 KY 12, 14 PA 06, 11 MA 08, 04 NY 17 A, 24 MN 06, ( Minnis and Lindner 2013) VKM F-4517 and VKM F-4515 ( Leushkin et al. 2015). Pseudogymnoascus russus can be differentiated from all other described species in clade B by its production of russet red colored exudate on PDA at 15 ° C. Additionally, it can be differentiated by P. papyriferae , P. australis , and P. griseus by its lack of arthroconidia. Pseudogymnoascus russus can also be differentiated from P. shaanxiensis by its smaller hyphal width (0.9–2.1 μm vs. 1.5–2.5 μm). Phylogenetically our P. russus isolates, strains 99 ASP 01 and 390 ASP, form a well-supported single clade with a bootstrap value of 88, separated from other taxa (Fig. 1 ). Sister to P. russus isolates there is an unidentified strain 11 MA 08; which we are not able to confirm whether it’s conspecific with P. irelandiae as we don’t have access to this isolate to analyze its culture and microscopic characteristics; however, we do know that their isolation sources are quite different, as 11 MA 08 was cultured from soil from bat hibernacula in Massachusetts, USA ( Minnis and Lindner 2013).

Figures

Figure 1. Maximum likelihood (ML) phylogenetic tree of Pseudogymnoascus based on the concatenated dataset of five genes (ITS, LSU, MCM 7, RPB 2, TEF 1). ML bootstrap values ≥ 70 are shown above branches. New species described here are highlighted in bold and red. The scale bar indicates 0.03 nucleotide changes per site.

Figure 2. ML phylogeny of Pseudogymnoascus based on an alignment of 1496 concatenated orthogroups with single-copy genes. ML bootstrap values ≥ 75 are shown above branches. New species are highlighted in bold and red. The scale bar indicates 0.09 amino acid changes per site.

Figure 7. Pseudogymnoascus russus sp. nov. colony morphology at 5 ° C and 15 ° C after 28 days on CMA, OA, PDA, and SDA.

Figure 8. Pseudogymnoascus russus sp. nov. A, B, C conidiophore D fertile hyphae bearing aleurioconidia E conidia. Scale bars: 10 µm.