Aquihelicascus songkhlaensis W. Dong, H. Zhang & K.D. Hyde
Index Fungorum number: IF557919; Facesoffungi number: FoF09261
Etymology: referring to songkhla, where the holotype was collected
Holotype: MFLU 18-1511
Saprobic on decaying wood submerged in freshwater. Sexual morph: Pseudostromata 380–430 μm high, 820–870 μm wide, scattered, comprising brown to black fungal tissues growing in cortex of host, with two locules, flattened at the basal region, horizontally arranged under the pseudostroma, visible on the host surface as blackened ostiolar dots. Locules 170–270 × 350–430 μm, immersed, lenticular, coriaceous, with ostiolate papilla. Ostiole converging at the centre, subcylindrical, black. Peridium of locules, 25–35 μm thick, comprising 8–11 layers of brown to dark brown, thin-walled, compressed cells of textura angularis, fusing with the host cells. Pseudoparaphyses 3 μm diam., numerous, cellular, hypha-like, hyaline, distantly septate. Asci 110–145(–160) × 16–18 μm (x̄ = 130 × 17 μm, n = 10), 8-spored, bitunicate, clavate, long pedicellate, up to 50 μm long, apically rounded with an indistinct ocular chamber. Ascospores 24–28 × 8–10 μm (x̄ = 25.7 × 9.4 μm, n = 20), overlapping biseriate, straight or slightly curved, hyaline, 1-septate, constricted at the septum, symmetrical, ellipsoidal with rounded ends, with 2–4 prominent big guttules when immature, smooth, thin-walled, lacking a mucilaginous sheath. Asexual morph: Undetermined.
Culture characteristics: On PDA, colony circular, reaching 10 mm in 13 days at 25 °C, white to pale grey from above, dark brown from below, surface rough, dry, raised, edge entire.
Material examined: THAILAND, Songkhla Province, on submerged wood in a stream, 10 May 2018, W. Dong, 20180508-1 (MFLU 18-1511, holotype), ex-type living culture MFLUCC 18-1154; ibid., 20180508-2 (HKAS 105006, isotype), ex-type living culture KUMCC 19-0022; Nakhon Si Thammarat Province, on submerged wood in a stream, 10 May 2018, W. Dong, hat6107-1 (MFLU 18-1716), living culture MFLUCC 18-1273; ibid., hat6107-2 (HKAS 105028), living culture KUMCC 19-0043; Songkhla Province, on submerged wood in a stream, 10 May 2018, W. Dong, hat8114-1 (MFLU 18-1702), living culture MFLUCC 18-1278; ibid., hat8114-2 (HKAS 105036), living culture KUMCC 19-0051.
Notes: Aquihelicascus songkhlaensis clusters with A. yunnanensis in the phylogenetic tree of Dong et al (2020). They share similar morphological characters of clavate asci, ellipsoidal, hyaline, 1-septate, symmetrical ascospores and are from freshwater habitats and they have overlapping ascospore size. However, A. songkhlaensis can be distinguished by its two-loculate pseudostromata contrasting with one-loculate in A. yunnanensis. There are 12, 16 and 14 nucleotide differences between ex-type strains of the two species in LSU, ITS and TEF sequence data, respectively.