Acanthocorticium brueggemannii Baltazar, Gorjón & Rajchenb., in Baltazar et al., Botany 93(8): 456 (2015)
Etymology: Named in honor of Fernando M. Brüggemann (Brazilian biologist), in recognition of his work for the research, conservation, and environmental education in the Parque Estadual da Serra do Tabuleiro, type locality of A. brueggemannii.
Diagnosis: Acanthocorticium brueggemannii differs from Aleurodiscus dextrinoideocerussatus Manjón et al. by wider acanthophyses with shorter apical projections, presence of halocystidia, lack of gloeocystidia, and globose, IKI– basidiospores.
Basidiome resupinate, adnate, cartilaginous hard when dry, up to 0.13 mm thick. Hymenophore smooth to tuberculate, even to rimose, pale gray (1C1, 1B1), gray (1D1) to grayish green (1D3), margin thinning out but defined, concolor with the hymenophore.
Basidiospores globose, hyaline, smooth, and thin-walled, with an inconspicuous apiculus, 5–6 µm diameter, IKI–, cyanophilous. Basidia not seen, basidioles few, cylindrical to clavate, hyaline, thin walled. Hyphal system monomitic, generative hyphae simple septate, pale yellowish, slightly thick-walled, 1.5–3.5 (–4) µm diameter. Halocystidia abundant in the subiculum and in the hymenium, rarely projecting, hyaline, finely echinulate at the capitate apex, IKI– to slightly dextrinoid, 3.4 (–4) µm diameter, with a resinous cap up to 12 µm diameter. Acanthophyses present in the subiculum and dominating the hymenium, cylindrical to clavate, hyaline, with short protuberances in the apical portion, (3–) 4.5–10 µm diameter, dextrinoid.
Distribution: Known only from the type locality.
Substrate: Dead unidentified hardwood.
Index Fungorum number: IF812889
Notes: Acanthocorticium brueggemannii is characterized by the resupinate, cartilaginous hard basidiome, smooth to tuberculate hymenophore with grayish tints, abundant halocystidia with echinulate apex and a resinuous cap, variably dextrinoid acanthophyses with short protuberances in the apical portion, and globose, hyaline, smooth, thin-walled, cyanophilous and IKI– basidiospores. Baltazar et al. 2015 could not find any basidia after persistent search, including the study of the specimens in fresh condition. The inner structure of the basidiomes suggests a catahymenium, but further studies with more specimens are desirable to confirm this. This is the only species of Acanthocorticium known at the time being. At first glance, A. brueggemannii is similar to Aleurodiscus dextrinoideocerussatus due to the dextrinoid acanthophyses which dominate the whole basidiome. However, acanthophyses of A. dextrinoideocerussatus are narrower ((4–) 5–7 µm diameter) and have longer apical projections than those of A. brueggemannii. Aleurodiscus dextrinoideocerussatus is also different due to the presence of gloeocystidia and amyloid basidiospores, and the whitish to cream-colored hymenophore. Furthermore, A. dextrinoideocerussatus is a member of Russulales along with most other species of Aleurodiscus s.l. (Larsson 2007; Bernicchia and Gorjón 2010).
Figure 1. Microscopic features of Acanthocorticium brueggemannii, (A) basidiospores, (B) acanthophyses, (C) generative hyphae, and (D) halocystidia.
Figure 2. Microscopic features of Acanthocorticium brueggemannii, JMB 2621 (holotype) in a section of the basidiome.