Protohydnum elasticum (Lowy) Spirin, 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 elasticum (Lowy) Spirin comb. nov.

Fig. 11 C

≡ Ductifera elastica Lowy , Mycotaxon 15: 97, 1982. Holotype. Brazil. Acre: Rio Branco , rotten wood, 11. X. 1980 Lowy BR 646 ( LSUM, isotype – NY 00738327 , studied).

Description.

Basidiocarps effused, up to 3 cm in widest dimension, smooth or indistinctly tuberculate, gelatinous, opaque, dirty ochraceous to brownish, 0.1–0.2 mm thick, in dry condition almost invisible, margin sharply delimited, adnate. Hyphal structure monomitic, hyphae hyaline, clamped; subicular hyphae thin- to slightly thick-walled, interwoven or subparallel, hardly discernible, 1.5–3.5 μm in diam., subhymenial hyphae thin-walled, ascending or interwoven, easily collapsing, 1.5–3 μm in diam. Gloeocystidia abundant, hyaline to yellowish, tubular-clavate, sometimes gradually tapering to the apex, embedded, (35 –) 36–92 (– 102) × (5.0 –) 5.1–8.7 (– 8.8) μm (n = 14 / 1). Hyphidia abundant, variably branched, 1–1.5 μm in diam. at the apex, forming a continuous layer up to 10 μm thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, 14.5–21 × 9.4–15.2 μm (n = 8 / 1), stalk up to 15 × 3.5–4 μm, sterigmata gradually tapering, up to 16 × 3–3.5 μm. Basidiospores smooth, thin-walled, broadly cylindrical to narrowly ovoid, slightly to moderately curved, (7.4 –) 7.8–11.0 (– 11.1) × (4.3 –) 4.6–5.8 (– 6.2) μm (n = 30 / 1), L = 9.10, W = 5.21, Q’ = (1.4 –) 1.5–1.9 (– 2.0), Q = 1.75.

Remarks.

The species was described as a member of Ductifera ( Lowy 1982) , although effused basidiocarps and pedunculate basidia of D. elastica indicate that Bourdotia could have been more appropriate for it. Roberts (2003) studied the type of D. elastica and concluded that it is conspecific with the European Exidiopsis (Bourdotia) galzinii (see under Protohydnum galzinii below). We rechecked the aforementioned type and concluded that D. elastica is similar to B. galzinii but cannot be considered its synonym. The main difference between these species is the spore width and shape – the basidiospores of D. elastica are certainly narrower and more regularly cylindrical than in B. galzinii . We therefore combine D. elastica in Protohydnum as a species of its own. The species is so far known only from the type locality in the Brazilian Amazon, and no verified sequences of P. elasticum currently exist.

Figures

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.