Mycena phaeonox A.C. Cooper, Desjardin & B.A. Perry, 2018

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, Phytotaxa 383 (1), pp. 1-47 : 22-24

8. Mycena phaeonox A.C. Cooper, Desjardin & B.A. Perry , spec. nov. ( Figs. 15 , 16 )

MycoBank no.: MB 825513

Holotype:—AFRICA. São Tomé, Parque Nacional Obo , Lagoa Amelia Trail N 00˚16.922’, E06˚36.062 ’, 14 April 2008, D. E. Desjardin and B. A. Perry, BAP 615 ( SFSU).

Etymology:— phaeus (Gr.) = dark coloured, nox (L.) = night – referring to the dark pileus pigmentation.

Diagnosis:— Pileus 7–30 mm diam, parabolic to campanulate, expanding to broadly campanulate with a flattened umbo, margin striate, becoming undulating to eroded in age; surface moist to dry, glabrous, felt-like with a 10× hand lens, disc dark greyish black initially, fading to dark ash grey (6–7F1–3) then eventually paler ash grey overall (6–7E1– 2), hygrophanous from disc outwards, becoming pale grey as it dries. Context thin, concolorous with pileus except white under disc. Lamellae ascending-adnate with a decurrent tooth, subdistant with 2 series of lamellulae, strongly interwoven, pale ash grey (6–7E1–2); edge paler grey, entire. Stipe 16–35 × 1–3.5 mm, central, terete, cylindrical, rarely flattened in larger specimens, hollow; surface dry, polished, minutely white-pruinose, pale grey, developing brown tones towards the base; base with white to yellow tomentum at point of attachment. Odour and taste indistinct. Bioluminescence undetected.

Basidiospores 6.4–8.0 (–8.8) × 4.0–5.6 μm [x m = 7.45 ± 0.72 × 4.79 ± 0.55 μm, Q = 1.29–2.20, Q m = 1.57 ± 0.15, n = 20, s = 1], ellipsoid, smooth, hyaline, amyloid, thin-walled. Basidia 20–36 × 5.6–8 μm, clavate, hyaline, inamyloid, thin-walled, 4-spored, rarely 2-spored, sterigmata up to 8 μm long. Basidioles clavate. Lamellar edge sterile. Cheilocystidia numerous, 30–86 × 9.6–22 μm, clavate to subcylindrical, smooth or with one or more knobby apical projections, hyaline, inamyloid, thin-walled; projections 2.4–7.2 × 2–7 μm, cylindrical to knob-like. Pleurocystidia absent. Pileipellis a cutis lacking pileocystidia; hyphae 4–13 μm diam, repent, cylindrical, smooth, hyaline, inamyloid, thin-walled, non-gelatinous; terminal cells undifferentiated, repent. Hypodermium composed of inflated hyphae up to 34 μm diam, ovoid to ellipsoid, with brown vacuolar pigments, dextrinoid, thin-walled, with rare laticiferous hyphae 2–6 μm diam with knob-like projections. Hymenophoral trama appearing sarcodimitic; many hyphae 2.4–6.5, thin-walled or some thick-walled (–1 μm), interwoven among inflated to fusiform hyphae up to 36 μm diam, hyaline, dextrinoid, non-gelatinous, thin-walled. Stipitipellis a cutis; cortical hyphae 0.8–8.8 μm diam, parallel, cylindrical, smooth, hyaline, dextrinoid, thin-walled; medullary hyphae 4–22 μm diam, smooth, hyaline, dextrinoid, thin-walled, some thick-walled (–0.8 μm), occasional laticiferous hyphae 4.8–8 μm diam with knob-like projections. Caulocystidia absent or rare, as undifferentiated, terminal cells or intercalary projections, solitary or in small clusters, erect to suberect, 24–130 × 4–7.2 μm, cylindrical, obtuse, rarely with a few knob-like outgrowths, hyaline, inamyloid, thin-walled. Clamp connections present in all tissues.

Habitat and known distribution:—Gregarious on rotting wood in upland forest. ( São Tomé). Only known from the holotype.

Notes:— Mycena phaeonox is distinguished by a campanulate, striate, dark grey pileus, ash grey, strongly interwoven lamellae, a minutely pruinose, pale grey stipe, amyloid basidiospores with mean 7.5 × 4.8 μm, broadly clavate, hyaline cheilocystidia with a few knobby projections, no pleurocystidia, sarcodimitic hymenophoral trama tissue, a cutis-type pileipellis of smooth, repent hyphae lacking pileocystidia, dextrinoid tissues, few, cylindrical caulocystidia, and growth on woody debris. In combination, these features indicate placement in sect. Mycena . It shows similarities to the north European M. maculata P. Karst , but the latter has basidiomata that become spotted reddish in age (maculate), less intervenose lamellae, larger basidiospores (8.1–9.8 × 5.2–6.3 μm), and more coarsely diverticulate cheilocystidia (Maas Geesteranus 1985). The poorly known M. plectophylla var. umbrina (Dennis) Dennis has similar macromorphology, but forms smaller basidiospores (6–7 × 3–3.5 μm), has a fertile lamellar edge lacking cheilocystidia, and grows on litter (as Dictyoploca, Dennis 1951 , 1970). Mycena phaeonox is similar to what Pegler (1977) called M. parabolica (Fr.) Quél. , a problematic European name, and we follow Maas Geesteranus (1988a: 238) in recognizing Pegler’s East African taxon as different from the European taxon.

Several Trogia species in the sense of Corner (1966, 1991) show affinities to M. phaeonox . Trogia subdistans Corner differs in a plano-umbilicate pileus, decurrent lamellae, clavate to ventricose cheilocystidia with a filiform apical projection, and pileocystidia and caulocystidia similar to the cheilocystidia ( Corner 1966). Trogia guadalupensis (Heim) Corner shows similar macromorphology, but has inamyloid, subglobose basidiospores, clavate to subventricose cheilocystidia lacking knobby projections, lacks a hypodermium, and has pileocystidia and caulocystidia similar to the cheilocystidia ( Corner 1991). Trogia atropruinosa Corner forms shorter and much narrower basidiospores (5.5–6.3 × 2.7–3 μm), clavate to ventricose cheilocystidia with a filiform apical projection and dark contents resulting in a darkpruinose lamellar edge, and distinctive pigmented pileocystidia and caulocystidia ( Corner 1966). No taxa similar to M. phaeonox were reported from Madagascar by Métrod (1949).

Pairwise comparisons of aligned, overlapping ITS sequences of the São Tomé specimen (BAP 615) with the top ten BLAST results show 94.7–95.9% similarity to eight sequences of uncultured mycorrhizal fungus genes, 96.6% similar to an uncultured fungus clone (GQ890481) from roots of Australian Dracophyllum secundum , and 95.8% similar to “uncultured Mycena genes” (LC013345) isolated from Japanese Gastrodia pubilabiata . Mycena phaeonox is sister to a sequence determined as M. plumbea P. Karst. sensu A.H. Smith from Colorado, USA (DQ494677), with limited support in the ITS phylogeny ( Fig. 2), somewhat distant from other members of sect. Mycena .

Figures

FIGURE 15. Basidiomata of Mycena phaeonox (BAP 615, Holotype). Scale bar = 10 mm.

FIGURE 16. Mycena phaeonox (BAP 615, Holotype). a. Basidiospores. b. Basidia and basidiole. c. Cheilocystidia. d. Caulocystidia. Scale bar = 10 μm.