Dematiodidymosporum aquaticum Y.S. Liang, W. Dong, K.D. Hyde & Doilom, in Dong et al., Fungal Diversity (2025)

Index Fungorum number: IF 903059; MycoBank number: MB 903059; Facesoffungi number: FoF 17152; Fig. 1

Etymology – in reference to the freshwater habitat of the holotype.

Holotype – MHZU 24-0827

Saprobic on dacaying, submerged wood. Sexual morph: Ascomata 220–250 µm high, 180–190 µm diam., clustered, erumpent to almost superficial, subglobose, black, glabrous, unilocular, central ostiolate, with shot papillate. Peridium 25–40 µm thick, two-layered, outer layer composed of several layers of dark brown to black, thick-walled, compressed cells of textura angularis, inner layer composed of several layers of pale brown to hyaline, thin-walled, large cells of textura angularis. Pseudoparaphyses 1–2 µm wide, numerous, cellular, sparsely septate, unbranched, hyaline. Asci 67–85 × 12.5–16.5 µm (x̄= 75 × 15 µm, n = 10), 8-spored, bitunicate, clavate, apically rounded, with a short, inflated subglobose pedicellate. Ascospores 12–16 × 5–7 µm (x̄= 13.5 × 6 µm, n = 30), biseriate, becoming uniseriate near the pedicel, loosely arranged in the asci, fusoid, straight, 1-septate, slightly constricted at the septum, darkened at the septum when mature, asymmetric, apical cell slightly wider and with rounded apex, basal cell slightly narrower and with tapering but rounded end, subhyaline to pale golden brown when young, becoming golden brown when mature, rough walled, verrucose both in early and mature stages, without conspicuous sheath when mounted in water. Asexual morph: undetermined.

Material examined – China, Guangdong Province, Guangzhou City, Baiyun District, Zhongluotan Town, Zhongkai University of Agriculture and Engineering, on submerged decaying wood of an unidentified plant, 23 March 2024, W. Dong, L8 (MHZU 24-0827, holotype); ex-type culture, ZHKUCC 24-1452.

GenBank accession numbers – ITS: PQ605120, LSU: PQ605122, SSU: PQ605121, tef1-a: PQ614179, rpb2: PQ614180.

Notes – Dematiodidymosporum aquaticum is the type and, thus far, the only species of Dematiodidymosporum. It represents a new genus in the Dictyosporiaceae due to its unique combined morphological characteristics of superficial ascomata, clavate asci with rounded apex and subglobose pedicellate, and golden brown, rough-walled, asymmetric ascospores loosely arranged in the asci, and mature ascospores with a darkened septum. Dematiodidymosporum aquaticum was isolated from submerged wood. Additional investigations with more collections are required to determine whether it is an obligate freshwater fungus.

Figure 1 – Dematiodidymosporum aquaticum (MHZU 24-0827, holotype). a Colonies on natural substrate. b Vertical section of ascoma. c Peridium. d Asci with pseudoparaphyses. e–g Asci. h Young ascospores. i Mature ascospores. Scale bars: b = 100 µm, c, e, h, i = 20 µm, d = 50 µm, f, g = 30 µm.