Oxydothis aquatica Y. Y. Yang & K.D. Hyde, sp. nov.

Index Fungorum number: IF 902262; Mycobank number: MB 902262; Facesoffungi number: FoF 15184; Fig. 1

Etymology – “aquatica” refers to the collection of from aquarium habitats of this fungus.

Holotype – HKAS 131230.

Saprobic on the dead stem of Trachycarpus fortunei. Asexual morph: Undetermined. Sexual morph: Ascomata 220–260×38–48 µm (x̅=243×45, n=5), solitary or clustered in groups, immersed, black, ellipsoidal, forming under slightly raised, split at maturity and contents overflow. Peridium 2–5 µm wide, outer cells merging with the hostepidermal cells, comprising dark brown to hyaline, walled cells of textura angularis. Asci 102–187×7–9 μm (x̅=148×8 μm, n=20), unitunicate, pedicellate, fasciculate, cylindrical, smooth-walled, subapical ring, J+, with a wedg-eshaped. Ascospores 54–69×3–4 µm (x̅=62×3.8, n=30), hyaline, fusiform, smooth-walled, guttulate, tapering gradually, 1–2-seriate (delete), tapering gradually from the center to the ends, centrally 1-septate, constricted at the septum, with pointed ends.

Material examined – China, Yunnan Province, Kunming City, Panlong District, on a dead stem of Trachycarpus fortunei in aquarium. 9 December 2021, Rong-Ju Xu, YYY183 (holotype: HKAS 131230).

GenBank numbers – ITS: OR809208, LSU: OR809209, SSU: OR809210

Notes – The phylogeny based on multi-gene analysis indicates that Oxydothis aquatica is a distinct clade from O. inaequalis with 100% ML,1.00 PP statistical support. Morphologically, O. aquatica differs from O. inaequalis by having short and narrow asci (102–187 × 7–9 μm vs. 200–285 × 11.25–12.5 µm), and small ascospores (54–69 × 3–4 µm vs. 78–87.5 × 5–7.5 µm). Additionally, O. aquatica having bundle arrangement ascospores, but O. inaequalis having 1–2 seriate ascospores. Oxydothis aquatica is similsr to O. calamicola and O. rhapidicola in its in asci and ascospore shape. However, Oxydothis aquatica differs from both species in forming subcircular blackened regions on the host surface, and ascospore more than slender. Oxydothis calamicola forms a black hollow oval on the host surface, O. rhapidicola forming globose to subglobose rims on the host surface, with dark ostiolar dots at the center.

Figure 1 – Oxydothis aquatica (HKAS 131230, holotype) a. Appearance of fruiting bodies on host substrate. b–c. Close-up of ascomata. d–e. Section of ascoma. f–g. Asci. h–m. Ascospores. Scale bars: d–e=50 μm, f=100 μm, g=50 μm, h–m=20 μm