Aquihelicascus yunnanensis W. Dong, H. Zhang & K.D. Hyde
Index Fungorum number: IF557921; Facesoffungi number: FoF09263
Etymology: referring to Yunnan, where the holotype was collected
Holotype: MFLU 18-1170
Saprobic on decaying wood submerged in freshwater. Sexual morph: Pseudostromata 150–180 μm high, 420–480 μm diam., scattered, comprising brown to black fungal tissues growing in cortex of host, uniloculate, lenticular, immersed with blackened ostiolar dots on the host surface. Ostiole central, opening rounded, periphysate. Peridium 15–25 μm thick, comprising several layers of brown to dark brown, thin-walled, compressed, elongate cells of textura angularis, pale brown to hyaline inwardly. Pseudoparaphyses 1.5–2.5 μm diam., numerous, cellular, hypha-like, short, hyaline, sparsely septate, unbranched. Asci 120–140 × 13.5–19 μm (x̄ = 132 × 17 μm, n = 10), 8-spored, bitunicate, clavate, apically narrowly rounded, with a distinct, trapezoidal chamber, long pedicellate, up to 40 μm. Ascospores 25–28 × 9–10.5 μm (x̄ = 27 × 10 μm, n = 10), biseriate, ellipsoidal, rounded at both ends, straight or slightly curved, hyaline, 1-septate, constricted at the septum, symmetrical, guttulate, two prominent guttules near the septa and with additionally smaller ones beside, smooth, thin-walled, lacking a mucilaginous sheath. Asexual morph: Undetermined.
Culture characteristics: On PDA, colony circular, reaching 5 mm in 15 days at 25 °C, white to grey from above, brown from below, surface rough, fluffy, with dense mycelium, dry, raised, edge entire.
Material examined: CHINA, Yunnan Province, Dehong, on submerged wood in a stream, 25 November 2017, G.N. Wang, H35A-1 (MFLU 18-1170, holotype), ex-type living culture MFLUCC 18-1025; ibid., H35A-2 (HKAS 101719, isotype), ex-type living culture KUMCC 18-0069.
Notes: Aquihelicascus yunnanensis clusters with A. songkhlaensis in the multigene phylogenetic analysis of Dong et al. (2020). However, the number of locules in pseudostromata, single gene comparison (see notes under A. songkhlaensis) and phylogenetic analysis separate them to be different species.
Aquihelicascus yunnanensis is morphologically similar to A. thalassioideus in having clavate asci, and ellipsoidal, hyaline, 1-septate, guttuate ascospores (Zhang et al. 2013). However, A. yunnanensis has a thinner peridium (15–25 μm vs. 70 μm) than A. thalassioideus. There are 10 and 32 nucleotide differences in LSU and ITS sequence data between A. yunnanensis (MFLUCC 18-1025) and A. thalassioideus (MFLUCC 10-0911), respectively, which indicates them to be different species.