Hydrophana sphaerospora (Bourdot & Galzin) V. Malysheva & V. Spirin, in Spirin et al., Nordic Journal of Botany 37: 8 (2019)
Diagnosis: Basidiocarps semitranslucent, effused, continuous, smooth or slightly tuberculate, gelatinous, hyaline or greyish, adnate, 0.05–0.2 mm thick, margin indistinct; detectable mineral inclusions absent.
Hyphal structure monomitic; hyphae clamped. Basal hyphae thin-walled, subparallel, 2–2.5 μm in diam.; subhymenial hyphae ascending, thin-walled, glued together, 1–2.2 μm in diam. Cystidia absent; hyphidia abundant, simple to branched, 0.7–1.5 μm in diam. at the apical part. Basidia 4-celled, (7.3–) 7.7–9.7 (–9.8) × (6.2–) 6.3–8.3 (–8.8) μm (n = 30/3), embedded; enucleate stalk up to 16 × 2–3 μm; sterigmata up to 16 × 1–2 μm. Basidiospores broadly ellipsoid to subglobose, (3.8–) 4.0–6.2 (–6.3) × (3.2–) 3.4–5.2 (–5.3) μm (n = 210/7), L = 4.60–5.22, W = 4.15–4.57, Q = 1.10–1.18.
Distribution and ecology. Europe (Denmark, France, Norway); fallen logs and twigs of deciduous trees in moist places.
Index Fungorum number: IF 829008
Notes: This species was described as Sebacina sphaerospora (Bourdot & Galzin 1924) and later moved to Myxarium (Reid 1973). Roberts (1998) suggested that M. sphaerosporum is a later synonym of Stypella glaira (Lloyd) P. Roberts. However, the data do not confirm these taxonomic replacements and show that S. sphaerospora is not closely related to either Myxarium spp. or S. glaira (= Ofella glaira in Spirin et al. 2019). Therefore, we have introduced a new genus for it. Morphologically, H. sphaerospora is very similar to Myxarium spp. except for the small, broadly ellipsoid to subglobose basidiospores. Differences between H. sphaerospora and O. glaira are more subtle: the latter species has on average longer spores with higher Q values and it occurs exclusively on coniferous hosts.
Figure 1. Combined phylogenetic nrITS+nrLSU topology from maximum likelihood analysis showing main lineages within Auriculariales. All sequences generated for this study are indicated in bold faces. Collection numbers of specimens are given for all sequences. Full red circle indicates clades that include taxa with sphaeropedunculate basidia (empty circle indicates absence of this feature). Support values (ML/BA) are given above the branches. Scale bar shows expected changes per site.