Neohelicascus submersus H. Yang, W. Dong, K.D. Hyde & H. Zhang
Index Fungorum number: IF557927; Facesoffungi number: FoF09269
Etymology: referring to submerged habitat of this fungus
Holotype: MFLU 20-0436
Saprobic on submerged wood. Sexual morph: Pseudostromata 485–540 μm high, 315–510 μm diam., scattered, comprising dark brown to black fungal tissues growing in cortex of host, immersed, unilocular, lenticular, flattened at the base, black, with wide ostiole, visible as elongate, prominent, black neck erumpent on the host surface. Neck 310–320 × 125–165 μm, central, cylindrical, with periphyses. Peridium 20–45 μm thick, comprising several layers of dark brown cells of textura epidermoidea. Pseudoparaphyses 1.5–2.5 μm wide, numerous, cellular, cylindrical, hyaline, indistinctly septate. Asci 120–165 × 17.5–21 μm ( = 143 × 19 μm, n = 10), 8-spored, bitunicate, fissitunicate, cylindrical to narrowly clavate, apically rounded, base of endoascus long, narrow and coiled within ectoascus, up to 150 μm long. Ascospores 23.5–31 × 8.5–11.5 μm, (= 27 × 10 μm, n = 30), obliquely arranged, overlapping uniseriate or occasionally biseriate, ellipsoidal to fusiform, slightly curved, 1-septate, constricted at the septum, upper cell slightly wider than lower cell, hyaline when young, become brown when mature, guttulate, thin-walled, smooth, covered by a distinct gelatinous sheath, 1.5–5.5 μm wide, showing 15–27 μm wide in Indian Ink. Asexual morph: Undetermined.
Cultural characteristics: Conidia germinated on PDA within 24 hours. Germ tubes arising from end of the ascospore. Colonies on PDA reaching 30 mm diameter in 30 days at 20–25 °C, initially white, turning reddish brown to dark brown after 15 days, with dense, hairy mycelium on the surface, with undulate, red margin, reverse reddish brown.
Material examined: CHINA, Yunnan Province, a small river in Puzhehei wetland, on submerged wood, 23 June 2019, H. Yang, P36 (MFLU 20-0436, holotype), ex-type living culture KUMCC 20–0153.
Notes: Neohelicascus submersus forms a well-supported clade with four species N. elaterascus, N. egyptiacus, N. unilocularis and N. uniseptatus (Dong et al. 2020). Neohelicascus submersus resembles N. elaterascus in having unilocular pseudostromata, and ellipsoidal to fusiform, brown ascospores with a distinct gelatinous sheath (Shearer 1993). However, N. elaterascus has shorter and wider asci (95–149 × (14–)18–25(–38) μm vs. 120–165 × 17.5–21 μm) and ascospores are mostly biseriate and verrucose in the holotype C-76-1 (Shearer 1993). Our two collections of N. elaterascus (MFLUCC 18-0993 and MFLUCC 18-0985) have smooth ascospores, which are similar to N. submersus, but phylogenetic analysis separate them as distinct species. Neohelicascus submersus is phylogenetically closest to N. unilocularis. They have overlapping ascospore size, however, N. submersus has longer and thinner asci (120–165 × 17.5–21 μm vs. 70–75 × 22–27 μm) than N. unilocularis (Zhang et al. 2015). Neohelicascus submerses has a distinct gelatinous ascospore sheath, 1.5–5.5 μm wide, showing 15–27 μm wide in Indian Ink, but it is lacking in N. unilocularis. There are two and 39 nucleotide differences in LSU and ITS sequence data between N. submerses (KUMCC 20–0153) and N. unilocularis (MJF 14020), which indicates them to be different species (Jeewon and Hyde 2016). (Notes from Dong et al. 2020)
Freshwater distribution: China (Dong et al. 2020)