Odontia parvispina Y.H. Mu, H.S. Yuan & Y.C. Dai, sp. nov.
Index Fungorum number: IF 840456; MycoBank number: MB 840456; Facesoffungi number: FoF 09973; Figs. 1, 2, 3
Etymology – The specific epithet “parvispina” refers to hymenophoral surface with very small spines.
Holotype – Yuan 10652
Basidiomata annual, resupinate, easily separable from the substrate, arachnoid, continuous, without odour or taste when fresh, becoming cottony upon drying, up to 0.25 mm thick. Hymenophoral surface yellowish brown to brown (5D8–6E8) when dry, smooth or hydnoid to the naked eye; spines conical, up to 0.06 mm long, 0.02–0.03 mm wide at the base, evenly distributed, 4–6 per mm, turning darker than subiculum. Subiculum mostly brown. Sterile margin determinate, byssoid, paler than hymenophore, brown. Rhizomorphs present in subiculum and margins, 10–60 μm diam.; rhizomorph surface rather smooth; hyphal structure in rhizomorphs dimitic, differentiated, of type C (according to Agerer 1987–2008), compactly arranged; generative hyphae in center of rhizomorph simple-septate, slightly thick-walled, 3–4 μm diam., colorless in KOH; skeletal hyphae at outer part of rhizomorph thick-walled, 1–2 μm diam., grayish yellow in KOH, cyanophilous, inamyloid. Hyphal structure subicular hyphae monomitic, generative hyphae simple-septate, thin- to slightly thick-walled, 3–4 μm diam., occasionally collapsed, without encrustation, grayish yellow in KOH, acyanophilous, inamyloid. Subhymenial hyphae simple-septate, thin-walled, 2–3 μm diam.; hyphal cells more or less uniform, colorless in KOH, acyanophilous, inamyloid. Spine tramal hyphae monomitic, generative hyphae with clamp connections, thick-walled, 3–5(–6) μm diam., grayish yellow in KOH, cyanophilous, inamyloid (Fig. 4).
Hymenium cystidia and cystidioles absent. Basidia 15–44 μm long and 3–8 μm diam. at apex, 2–4 μm at base, simple-septate at base, clavate, stalked, sinuous, with transverse septa, grayish yellow in KOH and in distilled water, bearing 4 sterigmata; sterigmata up to 5 μm long, 1–3 μm diam at base. Basidiospores (5.5–)6–7(–8)×(4–)5–6.4(–7) μm in lateral and frontal face, L=6.39 μm, W=5.68 μm, Q =1.13–1.15 (n=60/2), irregular subglobose frontal and ellipsoid lateral face, oil drops absent, verruculose, light brown in KOH and in distilled water, acyanophilous, inamyloid; warts usually grouped in 2 or more, bi- to trifurcate alike, 1–2 μm long. Chlamydospores absent.
Material examined – CHINA, Liaoning Province, Huanren County, Laotudingzi Nature Reserve, on fallen angiosperm trunk, 20 October 2015, H.S. Yuan (Yuan 10652, holotype); Kuandian County, Baishilazi Nature Reserve, on fallen angiosperm branch, 22 October 2015, H.S. Yuan (Yuan 10716).
GenBank numbers – Yuan 10652: ITS=MW033328, Yuan 10716: ITS=MW033329.
Notes – Odontia parvispina is closely related to O. fibrosa in the phylogenetic tree (Fig. 4) and share similar morphological and anatomical characteristics: annual, resupinate, arachnoid basidiomata, smooth or hydnoid hymenophoral surface, brown subiculum, the presence of rhizomorphs with dimitic hyphal system, thin- to slightly thick-walled and simple-septate generative hyphae in the subiculum and clavate basidia of similar size (Figs. 1, 2 and 3). However, O. fibrosa can be differentiated by thicker basidiomata (up to 0.4 mm vs. up to 0.25 mm in O. parvispina), dark brown and granulose hymenophoral surface when dry, longer spines (up to 1 mm vs. up to 0.06 mm in O. parvispina), simple-septate and wider hyphae (5–7 μm vs. 3–5 μm in O. parvispina) in spine trama and larger basidiospores (7.1–9×6.1–8 μm vs. 6–7×5–6.4 in O. parvispina). Odontia sparsa resembles O. parvispina in having resupinate and arachnoid basidiomata, a dimitic system in the rhizomorphs with simple-septate and slightly thick-walled generative hyphae and thick-walled skeletal hyphae and verruculose basidiospores. However, the former species differs by thin and clamped generative hyphae, the presence of skeletal hyphae in the subicular and reddish brown basidiospores in KOH with shorter warts (0.3–0.8 μm vs. 1–2 μm in O. parvispina) (Yuan et al. 2018).
Figure 1 – Odontia parvispina (Yuan 10652, holotype): Basidiomata
Figure 2 – Odontia parvispina (Yuan 10652, holotype): SEM of basidiospores
Figure 3 – Odontia parvispina (drawn from the holotype), microscopic structures. a Section through basidiomata. b Section through rhizomorph. c Basidiospores in frontal and lateral view
Figure 4 – Maximum likelihood tree illustrating the phylogeny of Odontia huanrenensis, O. parvispina and related taxa based on ITS sequence dataset. Fifty sequences are included in the analyses. Polyzellus multiplex SMI299 was selected as the outgroup taxa. Branches are labeled with maximum likelihood bootstrap support greater than 50% (MLBS), parsimony bootstrap proportions greater than 50% (MPBS) and Bayesian posterior probabilities greater than 0.95 (BYPP). The new species and new record are in bold