Cyphellostereum mucuyense V. Marcano 2022, sp. nov.
Creators: name: Marcano, Vicente
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Agaricales
Hygrophoraceae
Cyphellostereum
Cyphellostereum mucuyense

description: 2) Cyphellostereum mucuyense V. Marcano, sp. nov.; (Fig. 5)
Mycobank MB#838446
Diagnosis:— Sicut Dictyonema metallicum, sed cellulis quadrato-rhombici nullis differt. Thallus muscicola vel terricola, sat tenuis. Prothallus nullus. Hyphae fibulatae. Haustoria nulla. Hymenocarpus resupinatus. Hymenium N non reagens. Basidiosporae subglobosae, 5–7 μm crassae.
Type:— VENEZUELA. Mérida: Sierra Nevada de Mérida, San Jerónimo cloud forests, near Mucuy Alta, elev. 2150 m, terricolous; 30 October 2020, V. Marcano 20-567 (holotype MER, isotype B, private herb. V. Marcano).
Etymology:—The epithet refers to the locality where the type specimens were collected.
Description:— Thallus growing on and among bryophytes or soils, crustose-filamentous, dark green, developing a mat of ± individual to slightly interwoven fungal-cyanobacterial fibrils connected by a very thin hypothallus; prothallus absent. Fibrils horizontally arranged and closely appressed. Photobiont layer (50–120 μm) composed of cyanobacterial filaments covered by thin elongated fungal cells, not forming jigsaw-puzzle-shaped cells; cyanobacterial filaments not branched, composed of 8–10 μm wide and 4–9 μm high, green cells, mostly square to elongate–cylindrical, in chains, not penetrated by tubular fungal hyphae (haustoria); heterocytes rare, pale to slightly bright yellow, 7–8 μm wide and 4–5 μm high; cells of hyphal sheath regular in lateral outline, 2–4 μm thick; hyphae of medulla and hypothallus straight, hyaline, much branched, 3.5–5 μm thick. Clamp connections present, not common; hypothallus formed by interwoven, strongly agglutinate, generative hyphae.
Hymenophore (when fresh) developed as effuse patches, resupinate-corticioid, 30–80 mm diameter, white, without distinct margins, with finely arachnoid surface; composed of a paraplectenchymatous layer resting on hyphae emerging from supporting thallus; in section 40–50 μm thick, composed of 3.5–5 μm thick hyphae; hymenium composed of numerous, palisade–like basidioles and scattered basidia; basidioles 20–30 × 5–6 μm; basidia 25–40 × 5–7 μm; basidiospores subglobose, non-septate, hyaline, 5–7 μm.
Chemistry:—Thallus K–, C–, KC–, P–; medulla K–, C–, KC–, P–, N–, ER–; basidiocarp K–, C–, KC–, P–, N–, ER– (n = 6). No lichen compounds detected by TLC.
Distribution and Ecology:—This species is known only from the well-developed type collection. It was found growing on mosses and acid soils in shady and very humid rainforest at 2150 m (Fig. 4A). This is the first record of the genus Cyphellostereum in Venezuela.
Remarks:—Morphologically, C. mucuyense is a typical representative species of Cyphellostereum. It is characterized by an appressed filamentous thallus, a distinct, thin hypothallus, clamp connections, resupinate basidiomata (hymenophore) and absence of jigsaw-puzzle-shaped hyphal cells. Morphologically it resembles Dictyonema metallicum Lücking, Dal Forno & Lawrey (Lücking et al. 2013a: 22) in having appressed, horizontal fibrils and absence of a discernible medulla. The latter differs in the presence of a prothallus, an irregular photobiont layer, the dark greenish color of the cyanobacterial photobiont, a hyphal sheath formed by jigsaw-puzzle-shaped cells, and the absence of clamp connections. Cyphellostereum mucuyense could also be confused with D. obscuratum Lücking, Spielmann & Marcelli (Lücking et al. 2013a: 24) as both species are characterized by a strongly compressed mat of irregularly arranged, densely interwoven fibrils, but the latter species forms jigsaw-puzzle-shaped cells and lacks clamp connections (Lücking et al. 2013).
Anatomically, C. mucuyense agrees with other Cyphellostereum species in the simple hyphal sheath around the cyanobacterial filaments, the comparatively narrow filament cells, and the absence of haustoria (Yanez et al. 2012, Lücking et al. 2013a, Dal Forno 2015; Dal Forno et al. 2013, 2016). The tiny fibrils of C. mucuyense are also reminiscent of those of Cyphellostereum. However, the resupinate-corticioid hymenophore is more reminiscent of Dictyonema s.str. (Lücking & Timdal 2016). Another species confirmed in the latter genus based on molecular data, D. huaorani, also lacks jigsaw-puzzle-shaped hyphal cells and haustoria (Schmull et al. 2014). Molecular studies are needed to determine the position of this taxon in the Dictyonema clade.
description: Published as part of Marcano, Vicente, 2022, Eight new species of lichenized Basidiomycota in the genera Acantholichen, Cyphellostereum and Dictyonema s. str. (Agaricales, Hygrophoraceae) from northern South America, pp. 199-225 in Phytotaxa 574 (3) on pages 208-210, DOI: 10.11646/phytotaxa.574.3.1, http://zenodo.org/record/7380966