Protohydnum ocellatum Alvarenga & K. H. Larss., 2025

Spirin, Viacheslav, Malysheva, Vera, Viner, Ilya, Alvarenga, Renato Lúcio Mendes, Grebenc, Tine, Gruhn, Gérald, Savchenko, Anton, Grootmyers, Django, Ryvarden, Leif, Vlasák, Josef, Larsson, Karl-Henrik & Nilsson, R. Henrik, 2025, Additions to the taxonomy of the Auriculariales (Basidiomycota) with pedunculate basidia, MycoKeys 120, pp. 339-392 : 339-392

Protohydnum ocellatum Alvarenga & K. H. Larss. sp. nov.

Fig. 11 K

Holotype.

Brazil. Rondônia: Porto Velho, Cunião Ecological Station , angiosperm wood in lowland rain forest, 13.III.2012 Larsson 15431 * ( URM).

Etymology.

Ocellatus (Lat., adj.) – ocellate; in reference to abundant mineral inclusions.

Description.

Basidiocarps effused, up to 10 cm in widest dimension, tuberculate, gelatinous, semitranslucent, amber-yellow to ochraceous-reddish, 0.5–1 mm thick, containing numerous small whitish grains, in dry condition vinaceous-brown, vernicose, margin sharply delimited, adnate or partly detaching. Hyphal structure monomitic, hyphae hyaline, clamped, thin-walled, homogeneous throughout, ascending, rather tightly arranged, 3–5 μm in diam. Cystidia absent. Hyphidia abundant, richly branched, 1–1.5 μm in diam. at the apex, usually forming a continuous layer up to 15 μm thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, (12 –) 13–14.5 (– 15) × (8.2 –) 8.8–11.1 (– 11.3) μm (n = 20 / 1), stalk up to 30 × 3–5 μm, sterigmata gradually tapering, up to 12 × 3–4 μm. Basidiospores smooth, thin-walled, cylindrical to subfusiform, (7.7 –) 7.9–10.2 (– 10.3) × (3.1 –) 3.6–4.8 (– 4.9) μm (n = 30 / 1), L = 8.91, W = 4.07, Q’ = (1.8 –) 1.9–2.6 (– 2.7), Q = 2.20, cytoplasm usually aguttulate.

Distribution and ecology.

South America ( Brazil); decayed angiosperm wood.

Remarks.

Protohydnum ocellatum is introduced here as a sibling species of P. cartilagineum (Figs 1 , 2 ). The species are confusingly similar under the microscope, and they are phylogenetically closely related. The only reliable morphological difference is the hymenophore construction: the hymenophore is nearly smooth in P. ocellatum but consists of robust (up to 3 mm long), regularly distributed spines in P. cartilagineum . Nevertheless, this striking macroscopic difference and the substantial genetic distance (2.6 % difference in the LSU region) allow us to distinguish between these two species. Protohydnum ocellatum has so far only been found in the type locality in Brazil.

Figures

Figure 1. Bayesian majority-rule consensus ITS + LSU-based tree of the Auriculariales overlaid with bootstrap support values from the maximum likelihood analysis. Support values are given as Bayesian posterior probabilities / ML bootstrap percentages. Species with stalked basidia are marked with a red X. I – Protohydnum clade; II – Elmerina clade; III – Hydrophana clade; IV – Endoperplexa – Mycostilla clade; V – Protoacia – Gelacantha clade; VI – Protomerulius clade; VII – Myxarium clade. The Sebacinales (Ditangium P. Karst., Sebacina, and Serendipita P. Roberts spp.) and Exidiopsis gloeophora were used as outgroups.

Figure 2. Bayesian majority-rule consensus ITS-based tree of the Protohydnum clade. Support values are given as Bayesian posterior probabilities. Basidiodendron spp. were used as an outgroup.

Figure 11. Basidiospores of: A. Protohydnum album (specimen Miettinen 196583); B. P. aureum (holotype); C. P. elasticum (holotype); D. P. elevatum (holotype); E. P. erumpens (holotype); F. P. galzinii (three left – specimen Miettinen 15900.4, three right – lectotype of S. galzinii); G. P. lactescens (four left – specimen TAAM 192048, three right – holotype of S. lactescens); H. P. livescens (specimen Spirin 13913); I. P. microperum (holotype); J. P. nudum (holotype); K. P. ocellatum (holotype); L. P. pallidum (holotype); M. P. pululahuanum (three left – lectotype, three right – specimen FH 00783538); N. P. sucinum (three left – lectotype of A. brasiliensis, three right – specimen BPI 701268); O. Protomerulius amiliavi (holotype); P. P. deceptorius (holotype). Scale bar: 10 µm.