Mycena oboensis A. C. Cooper, Desjardin & B. A. Perry 2018, spec. nov.
Creators: name: Cooper, Alexandra C.
name: Desjardin, Dennis E.
name: Perry, Brian A.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Agaricales
Mycenaceae
Mycena
Mycena oboensis

description: 13. Mycena oboensis A.C. Cooper, Desjardin & B.A. Perry, spec. nov. (Fig. 23)   
MycoBank no.: MB 825515  
Holotype:—AFRICA. São Tomé, Parque Nacional Obo, Lagoa Amelia Trail, N 00˚16.922’, E06˚36.062’, 25 April 2008, D.E. Desjardin and B.A. Perry, BAP 669 (SFSU).  
Etymology:—referring to the site where the holotype was collected, Parque Nacional Obo.  
 Diagnosis:— Pileus 1.5–3 mm diam, initially paraboloid, becoming plane with a central depression, striate; surface dull, dry, minutely granulose, disc with black pruinae, less pruinose towards the margin, white. Lamellae adnate with a short decurrent tooth, subdistant with 1 series of lamellulae, broad, white. Stipe 8–14 × <0.5 mm, central, terete, cylindrical, arising from a small, pubescent basal disc; surface dull, dry, pubescent, white. Odour and taste not recorded. Bioluminescence undetected.   
 Basidiospores (6.4–) 7.2–8.8 × (4.0–) 4.8–5.6 μm [x m = 7.92 ± 0.73 × 4.84 ± 0.41 μm, Q = 1.33–1.83, Q m = 1.64 ± 0.12, n = 20, s = 1], ellipsoid, smooth, hyaline, amyloid, thin-walled. Basidia 11.2–16.8 × 7.2–10.4 μm, clavate, hyaline, inamyloid, thin-walled, 2-spored, sterigmata up to 1.5 μm long. Basidioles clavate. Cheilocystidia absent. Pleurocystidia absent. Pileipellis a cutis with acanthocysts and cherocytes; hyphae 2.4–4.0 μm diam, repent, cylindrical, smooth, hyaline, dextrinoid, thin-walled, non-gelatinous. Cherocytes scattered, 21–51 × 18–39 μm, globose to ovoid or pyriform, with knob-like projections over the upper half, apically thick-walled (3–10 (–23) μm), walls hyaline, contents greyish brown; projections 1.5–5 × 1.5–3.2 μm, solid. Acanthocysts common, 15.2–39 × 11.2–24 μm, globose, densely spinulose, thin-walled, hyaline, inamyloid; spinulae 0.8–1.6 × 0.5–0.8 μm. Marginal cystidia common, 16–53 × 10.4– 14.4 μm, clavate to fusiform, densely spinulose on the upper half or apex, thin-walled, hyaline, inamyloid; spinulae 0.8–1.6 × 0.5–0.8 μm. Hypodermium composed of inflated hyphae up to 21 μm diam, hyaline, inamyloid, thin-walled. Hymenophoral trama hyphae 2.4–8.8 μm diam, hyaline, dextrinoid, non-gelatinous, thin-walled. Stipitipellis a cutis; cortical hyphae 2.4–7.2 μm diam, parallel, cylindrical, hyaline, dextrinoid, thin-walled; medullary hyphae 9.6–29 μm diam, smooth, hyaline, dextrinoid, thin-walled. Caulocystidia abundant; 23–79 × 5.6–10.4 μm, cylindrical to fusiform, densely spinulose, hyaline, inamyloid, thin-walled; spinulae 1.6–2.4 × 0.8–1.6 μm. Clamp connections present in all tissues.   
Habitat and known distribution:—Gregarious on decaying seed of undetermined dicotyledonous tree in upland forest. (São Tomé). Only known from the holotype.  
 Notes:— Mycena oboensis is distinguished by tiny basidiomata with a white, striate pileus with scattered black pruinae, white, adnate lamellae with a decurrent tooth, a white, pubescent stipe arising from a small basal disc, basidiospores with mean 7.9 × 4.8 μm (Q = 1.6), 2-spored basidia, an absence of cheilocystidia and pleurocystidia, pileipellis with acanthocysts, very thick-walled cherocytes with brown contents and knobby projections, distinctive marginal cystidia, and cylindrical caulocystidia covered with spinulae. The macromorphology of M. oboensis is nearly indistinguishable from that of M. lasiopus, but the latter has a more grey pileus, shorter stipe (up to 7 mm), grows on sticks, has longer basidiospores with mean 9 × 4.8 μm (Q = 1.9), spinulose cheilocystidia, irregular-shaped cherocytes with tiny spinulae, lacks distinctive marginal cystidia, and has much longer caulocystidia with apically more sparse spinulae. The European M. rhenana Maas Geest. & Winterh. shows some affinities with M. oboensis (lacks cheilocystidia), but forms a pileus without black pruinae, has narrower basidiospores (3.8–4.3 μm), 4-spored basidia, non-spinulose caulocystidia, and lacks cherocytes (Maas Geesteranus & Winterhoff 1985).   
 Pairwise comparisons of aligned, overlapping ITS sequences of the São Tomé specimen (BAP 669) with the top ten BLAST results show 88.2% similarity to four sequences determined as M. corynephora, a European species in sect. Sacchariferae. Interestingly, the ITS sequence of M. oboensis is only 71.2% similar to that of M. lasiopus because of multiple insertions in M. oboensis. In the ITS phylogeny (Fig. 2), M. oboensis clusters with two additional members of sect. Sacchariferae from ST&P (M. lasiopus, M. alphitophora) in a clade with other members of the section (92% BS, 1.0 PP support).
description: Published as part of Cooper, Alexandra C., Desjardin, Dennis E. & Perry, Brian A., 2018, The genus Mycena (Basidiomycota, Agaricales, Mycenaceae) and allied genera from Republic of São Tomé and Príncipe, West Africa, pp. 1-47 in Phytotaxa 383 (1) on page 31, DOI: 10.11646/phytotaxa.383.1.1, http://zenodo.org/record/13724481