Protohydnum lactescens (Burt) Spirin & V. Malysheva, 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 lactescens (Burt) Spirin & V. Malysheva comb. nov.

Figs 10 A , 11 G

≡ Sebacina lactescens Burt , Annals of the Missouri Botanical Garden 13: 336, 1926. Holotype. Grenada. Grand Etang , [angiosperm branch], 1912–1913 Thaxter 153 ( FH 00488322 , studied).

Description.

Basidiocarps first adpressed-orbicular, up to 1 cm in diam., gelatinous, semitranslucent, pale ochraceous or greyish to brownish, 1–2 mm thick, then fusing together and forming compound effused basidiocarps up to 5 cm in diam., in dry condition brown and rather tough, margin adnate or partly detaching. Hyphal structure monomitic, hyphae hyaline, clamped; context hyphae thin-walled, interwoven or subparallel, anastomosing, embedded in gelatinous matrix, 2–4 μm in diam., subhymenial hyphae thin-walled, ascending or interwoven, 1.5–3 μm in diam. Gloeocystidia abundant, hyaline to yellowish or brownish, tapering or more rarely tubular-clavate, embedded or only slightly projecting (up to 10 μm) above hymenial layer, 48–112 × 5–11 μm. Hyphidia abundant, richly branched, 1–2 μm in diam. at the apex, forming a continuous layer up to 25 μm thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, sessile or rarely with a reduced stalk up to 4 × 3 μm, (18 –) 19–26.5 (– 29) × (10.8 –) 11.7–16.0 (– 18.0) μm (n = 30 / 3), sterigmata gradually tapering, up to 20 × 3.5–4 μm. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, occasionally slightly curved, (9.4 –) 9.9–15.6 (– 16.8) × (5.8 –) 5.9–8.3 (– 8.9) μm (n = 90 / 3), L = 13.05–14.04, W = 6.77–7.33, Q’ = (1.4 –) 1.5–2.4 (– 2.5), Q = 1.78–1.99.

Distribution and ecology.

North America ( USA – California, the Caribbean – Grenada); decayed angiosperm wood.

Remarks.

This species was originally described from the Caribbean ( Burt 1926) and later placed among the synonyms of Ductifera sucina ( Wells 1957). We restudied the type specimens of both Sebacina lactescens and Exidia sucina (see under Protohydnum sucinum below) and concluded that they belong to two different species. Protohydnum lactescens produces effused basidiocarps, while they are cerebriform-exidioid in P. sucinum . Microscopically, the species can be easily separated based on size of gloeocystidia (much shorter in P. lactescens than in P. sucinum ), basidia, and basidiospores (considerably larger in P. lactescens than in P. sucinum ). DNA sequences of D. sucina published by Weiß and Oberwinkler (2001) and Wells et al. (2004) represent P. lactescens instead. Wells (1957) listed Exidia cystidiata Olive as another synonym of D. sucina . We did not study its type; as we could judge from the protologue, it is likely that E. cystidiata is a synonym of P. lactescens .

Figures

Figure 10. Microscopic structures of: A. Protohydnum lactescens (specimen TAAM 192048) (hymenial cells and tramal hyphae); B. P. livescens (specimen Spirin 13913) (hymenial cells and subhymenial hyphae); C. P. pallidum (holotype) (gloeocystidia and a basidium); D. P. sucinum (lectotype) (1 – basidia and basidiospores; 2 – gloeocystidia). Scale bar: 10 µm.

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.