Mycena aff. discobasis Métrod (1949: 131)

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 : 14-16

3. Mycena aff. discobasis Métrod (1949: 131) ( Figs. 7 , 8 )

Description:— Pileus 13–18 mm diam, broadly convex to plano-convex, centrally depressed, striate to depression;

surface glutinous to viscid, glabrous, shiny, disc pale greyish white to light yellowish brown (5D5) or with a brown ring, pale watery whitish grey or white away from disc. Context <1 mm thick, concolorous with pileus. Lamellae free to subfree, close with 1–2 series of lamellulae, moderately broad (1–1.5 mm), white. Stipe 15–19 × 1–2 mm, central,

terete, cylindrical, hollow, arising from a small (3 mm diam), pale yellowish brown (C–D5) basal disc; surface dry,

pruinose overall, white or watery white grey. Odour indistinct; taste not determined. Bioluminescence undetected.

Basidiospores (6.4–) 7–8 (–9.5) × (3.2–) 4.0–5.1 (–5.6) μm [x mr = 7.3 × 3.9–4.6 μm, x mm = 7.3 ± 0 × 4.22 ± 0.5, Q = 1.4–2.3, Q mr = 1.61–1.88, Q mm = 1.75 ± 0.2, n = 20–30, s = 2], ellipsoid, smooth, hyaline, weakly amyloid, thin-walled. Basidia 12.8–26 × 5.6–8.8 μm, clavate, hyaline, inamyloid, thin-walled, 4-spored, rarely 2-spored, sterigmata up to 4.8 μm long. Basidioles clavate. Lamellar edge sterile. Cheilocystidia numerous, 38–69 × 11–18 μm, broadly clavate to fusiform, often mucronate, hyaline, inamyloid. Pleurocystidia absent. Pileipellis an ixolattice (sensu Hesler and Smith 1979: 49) of hyphae and differentiated terminal cells; hyphae 0.8–4 μm diam, irregular, cylindrical, smooth,

embedded in a gel layer up to 140 μm thick, hyaline, inamyloid, thin-walled. Terminal cells numerous; 31–78 × 4.0–14

μm, clavate, densely spinulose, embedded in upper portion of gel layer, hyaline, inamyloid, thin-walled; spinulae 0.8–

7.2 × 0.5–1.0 μm, cylindrical. Pileus marginal cells not differentiated from terminal cells. Hypodermium composed of inflated cells up to 25 μm diam, globose to ovoid, smooth, hyaline, dextrinoid, thin-walled. Hymenophoral trama regular to subregular; hyphae 1.6–23 μm diam, hyaline, dextrinoid, non-gelatinous, thin-walled. Stipitipellis a cutis;

cortical hyphae 1.6–11.2 μm diam, parallel, cylindrical, hyaline, inamyloid, thin-walled; medullary hyphae 7.2–26

μm diam, smooth, dextrinoid, thin-walled, with rare laticiferous hyphae up to 4 μm diam with knob-like projections.

Caulocystidia abundant; 49–142 × 9.6–22 μm, fusiform to narrowly cylindrical, hyaline, inamyloid, thin-walled.

Clamp connections present in all tissues.

Habitat and known distribution:—Solitary on decaying dicot wood in secondary upland and primary forest. ( São Tomé).

Material examined:—AFRICA. São Tomé, Macambrara radio antenna area, N00˚16.557’, E06˚36.326’, 25 April 2008, D.E. Desjardin and B.A. Perry, BAP 658 ( SFSU) ; same location, 11 April 2008, D.E. Desjardin, DED 8211 ( SFSU) .

Notes:—The present material is characterized by a glutinous, striate, plano-convex-depressed, white pileus with greyish white to yellowish brown disc and striate, subfree lamellae, a dry, pruinose, white stipe that arises from a well-developed basal disc, basidiospores with mean 7.3 × 4.2 μm, broadly clavate to fusiform cheilocystidia, no pleurocystidia, an ixolattice-type pileipellis with clavate, densely spinulose terminal cells, no differentiated pileus marginal cells, fusiform caulocystidia, and growth on wood. It differs from the original description and from a description of material from São Paulo, Brazil determined as M. discobasis , in forming smaller basidiospores. Métrod (1949) reported the basidiospores of Madagascar material as 7.5–9.5 × 6.5 μm, while Desjardin et al. (2007) reported them from Brazil material as 9–10.5 × 6–7.5 μm. Neither of the latter papers mentioned differentiated pileus marginal cells. Mycena chlorophos (Berk. & M.A. Curtis) Sacc. and M. margarita (Murrill) Murrill , two bioluminescent members of sect. Exornatae , differ subtly from the present material in presence of distinctive pileus marginal cystidia and ITS sequence data. Desjardin et al. (2007) report M. discobasis from Brazil as bioluminescent, whereas the São Tomé specimens were not bioluminescent.

Pairwise comparisons of aligned, overlapping ITS sequences of Mycena aff. discobasis (BAP 658, DED 8211) with the top ten BLAST results indicate 93.4–94.0% similarity to ten sequences of M. chlorophos . ITS sequences of M. margarita are not available for comparison. In the ITS phylogeny ( Fig. 2), Mycena aff. discobasis is sister to M. chlorophos with 100% BS and 1.0 PP support.

Figures

FIGURE 7. Basidiomata of Mycena aff. discobasis (DED 8211). Scale bar = 10 mm.

FIGURE 8. Mycena aff. discobasis (DED 8211). a. Basidiospores. b. Basidia. c. Cheilocystidia. d. Pileipellis hyphae. e. Caulocystidia. Scale bar = 10 μm.