Mycena solis 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 : 16-17

4. Mycena solis A.C. Cooper, Desjardin & B.A. Perry , spec. nov. ( Figs. 9 , 10 )

MycoBank no.: MB 825511

Holotype:—AFRICA. São Tomé, Macambrara radio antenna area, elevation 1300 m, N00˚16.557’, E06˚36.326’, 11 April 2008, D.E. Desjardin and B.A. Perry, BAP 592 ( SFSU).

Etymology:— sol (L.) = sun – referring to the sun yellow colour of the pileus surface, and the radiating striations like the sun’s rays.

Diagnosis:— Pileus 8–14 mm diam, hemispherical to parabolic when young, expanding to obtusely conical or campanulate, margin decurved to upturned, striate to sulcate; surface moist, glabrous, disc and striations disc and striations yellowish brown to brownish yellow (4–5C5–6), yellowish grey (3–4B5–6) towards the margin, pale grey at margin and between striations. Context thin; concolorous with the pileus. Lamellae ascending-adnate with a short decurrent tooth, subdistant (12–14) with 1–2 series of lamellulae, pale greyish white to pale cream; edge smooth, concolorous. Stipe 30–48 × 1–1.5 (apex) × 2–2.5 (base) mm, central, terete, subcylindrical or enlarged downward, inflated and twisted in larger specimens; surface dry, polished, smooth, glabrous, yellowish brown (3–4B–C5–6), some with pale grey apex, some with brown tones at the base, attached to substrate with scant, short, white, non-radiating fibrils; latex absent. Odour and taste indistinct. Bioluminescence undetected.

Basidiospores 7.2–8.8 (–9.6) × 4.0–4.8 μm [x m = 8.05 ± 0.7 × 4.36 ± 0.41 μm, Q = 1.50–2.20, Q m = 1.86 ± 0.12, n = 22, s = 1], ellipsoid, smooth, hyaline, amyloid, thin-walled. Basidia 19–24 × 4.8–5.6 μm, clavate, hyaline, inamyloid, thin-walled, 4-spored, sterigmata up to 8.8 μm long. Basidioles clavate. Lamellar edge sterile. Cheilocystidia of 2 types; 1) 30–59 × 7.2–10.4 μm, clavate to narrowly lageniform or fusoid, many with an apical papilla, hyaline, inamyloid, thin-walled, 2) 30–49 × 7.2–10.4 μm, clavate to narrowly lageniform, fusiform or cylindrical, with few to numerous finger-like projections, hyaline, inamyloid, thin-walled; projections 1.6–8 × 0.8–1.6 μm, cylindrical. Pleurocystidia abundant, similar to type 1 cheilocystidia. Pileipellis a cutis; hyphae 0.8–2.4 μm diam, repent, cylindrical, irregularly diverticulate with finger-like projections, hyaline, inamyloid, thin-walled, non-gelatinous; diverticula 1.6–4 × 0.8–1.6 μm, cylindrical. Hypodermium of inflated hyphae up to 37 μm diam, ovoid to globose, hyaline, dextrinoid, thin-walled. Hymenophoral trama subregular to irregular; hyphae 3.2–8.8 μm diam, hyaline, dextrinoid, non-gelatinous, thin-walled. Stipitipellis a cutis; cortical hyphae 1.4–2.4 μm diam, parallel, cylindrical, diverticulate with finger-like projections, hyaline, dextrinoid, thin-walled, diverticula 2.4–4 × 0.8–2.4 μm, cylindrical; medullary hyphae 6.4–24 μm diam, smooth, dextrinoid, thin-walled; interspersed with laticiferous hyphae up to 8.8 μm diam with knob-like projections 1.6–4 × 4–6 μm. Caulocystidia absent. Clamp connections present in all tissues.

Habitat and known distribution:—Gregarious to scattered on woody debris in upper elevation primary forest. ( São Tomé). Only known from the holotype.

Notes:— Mycena solis is distinguished by a small, sulcate, campanulate, yellowish brown pileus, ascending-adnate, subdistant, pallid, lamellae without coloured edge, a glabrous, yellowish brown stipe, amyloid basidiospores with mean 8 × 4.4 μm, two types of relatively narrow (7.2–10.4 μm) cheilocystidia, clavate to lageniform or fusiform pleurocystidia, diverticulate pileipellis and stipitipellis hyphae, no differentiated caulocystidia, and growth on woody debris. In combination, these features indicate placement in sect. Fragilipedes , allied with a few yellow-pigmented species, such as M. citrinomarginata Gillet , M. junquillina Dennis , and M. luteola Maas Geest. & de Meijer. Mycena citrinomarginata , a north temperate species, differs in forming yellow-marginate lamellae, differentiated caulocystidia, and no pleurocystidia ( Maas Geesteranus 1988a). Mycena junquillina forms basidiomata with sulphur yellow lamellae, a shorter (5–15 mm), xanthine orange, pruinose stipe, basidiospores with mean 7.4 × 5 μm, more consistently fusiform hymenial cystidia, and hair-like caulocystidia (Pegler 1983). Mycena luteola , described from Paraná, Brazil, forms much smaller (1.5–4 mm diam) pileus, a pale straw-coloured, puberulous stipe that arises from a patch of radiating fibrils, broader cheilocystidia (10–15 μm), stipitipellis hyphae with broader and longer diverticula, some thick-walled hair-like caulocystidia, thick-walled (–2 μm) stipe medullary hyphae, and growth on leaves ( Maas Geesteranus and de Meijer 1997).

The ITS sequence of M. solis (BAP 592) was rather short (380 BP) and of poor quality. In pairwise comparisons with the top ten BLAST results, M. solis showed 97.7% similarity to Mycena cf. sanguinolenta (JX434650), and 96.3% similarity to nine uncultured Mycena clones. In the ITS phylogeny ( Fig. 2), M. solis is sister to M. sanguinolenta (JF908370 from Spain; a species with marginate lamellae and reddish brown latex in sect. Sanguinolentae) in a well-supported clade (97% BS, 1.0 PP).

Figures

FIGURE 9. Basidiomata of Mycena solis (BAP 592, Holotype). Scale bar = 10 mm.

FIGURE 10. Mycena solis (BAP 592, Holotype). a. Basidiospores. b. Basidia. c. Cheilocystidia of two types. d. Pileipellis hyphae. e. Stipitipellis hyphae. Scale bar = 10 μm.