Mycena longinqua 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 : 24-26

9. Mycena longinqua A.C. Cooper, Desjardin & B.A. Perry , spec. nov. ( Figs. 17 , 18 )

MycoBank no.: MB 825514

Holotype:—AFRICA. Príncipe, Dois Irm ẽos area around 100 meters, N01˚34.89 ’, E07˚25.548 ’, 23 April 2008, D. E. Desjardin and B. A. Perry, BAP 648 ( SFSU).

Etymology:— longinquus (L.) = outlying – referring to the outlier position of the species within section Polyadelphia , because of the non-diverticulate stipitipellis cortical hyphae and unusual caulocystidia.

Diagnosis:— Pileus 1.5–3 mm diam, paraboloid, margin entire, striate; surface glabrous, hygrophanous, dark grey initially fading to brownish grey with age, margin pale grey. Lamellae ascending, adnate, subdistant with 2 series of lamellulae, pale grey; edge paler. Stipe 3–8 × <0.5 mm, central, terete, cylindrical, arising from a small basal disc, covered with short white hairs; surface glabrous, smooth, pearlescent, pale whitish grey. Odour and taste indistinct. Bioluminescence undetected.

Basidiospores 6.0–7.2 × 4.0–4.8 μm [x m = 6.94 ± 0.42 × 4.40 ± 0.41 μm, Q = 1.33–1.80, Q m = 1.59 ± 0.21, n = 20, s = 1], broadly ellipsoid, smooth, hyaline, amyloid, thin-walled. Basidia 12.8–17 × 5.6–7.2 μm, clavate, hyaline, inamyloid, thin-walled, 2-spored, sterigmata up to 3.2 μm long. Basidioles clavate. Lamellar edge mostly sterile. Cheilocystidia abundant; 18–25 × 12–20 μm, clavate, apically to entirely spinulose, hyaline, inamyloid, thin-walled; spinulae 0.8–1.6 × 0.5–0.8 μm, cylindrical. Pleurocystidia absent. Pileipellis a cutis with terminal cells; hyphae 4–16 μm diam, repent, cylindrical, densely spinulose, hyaline, inamyloid, thin-walled, non-gelatinous; spinulae 0.8–1.6 × 0.5–0.8 μm, cylindrical. Terminal cells 34–76 × 8.0–24 μm, broadly clavate, densely spinulose. Hypodermium of inflated hyphae up to 29 μm diam, ovoid, hyaline, dextrinoid, thin-walled. Hymenophoral trama subregular to irregular; hyphae 1.6–8 μm diam, hyaline, dextrinoid, non-gelatinous, thin-walled. Stipitipellis a cutis; cortical hyphae 1.6–4.8 μm diam, parallel, cylindrical, smooth or with sparse diverticula, hyaline, dextrinoid, thin-walled; medullary hyphae 8.8–19 μm diam, smooth, dextrinoid, thin-walled. Caulocystidia numerous, scattered; 29–90 × 6–11 (base) × 1.6–2.4 (filamentous apex) μm, irregularly cylindrical to filamentous with a broader base, with apical finger-like projections, hyaline, inamyloid, thin-walled; apical projections 0.8–3.2 × 0.5–0.8 μm. Clamp connections observed in all tissues.

Habitat and known distribution:—Gregarious on coconut hulls in secondary, coastal forest. ( Príncipe). Only known from the holotype.

Notes:— Mycena longinqua is characterized by a tiny, glabrous, striate, greyish brown pileus, ascending-adnate lamellae, a glabrous, whitish grey stipe that arises from a small basal disc, broadly ellipsoid, amyloid basidiospores with mean 7 × 4.4 μm, 2-spored basidia, very broadly clavate, densely spinulose cheilocystidia, no pleurocystidia, dextrinoid tissues, a cutis-type pileipellis of densely spinulose hyphae with distinctively clavate terminal cells, no clamp connections, unusual caulocystidia with a swollen base and apically diverticulate filamentous appendage, and growth on coconut debris. Although the caulocystidia with filamentous appendages are unusual and the stipe cortical hyphae lack diverticula, other morphological features suggest closest affinity to members of sect. Polyadelphia , where the taxon is tentatively accepted. Mycena longinqua differs from all described temperate species in the section, viz., M. polyadelpha (Lasch) Kühner , M. alniphila Robich , and M. capillaris (Schumach.) P. Kumm. ( Maas Geesteranus 1986, Robich 2003). Mycena tuberifera Maas Geest. & de Meijer , described from Paraná State, Brazil, differs mainly in forming larger basidiospores (8.9–10.3 × 4.5–4.9 μm) from 4-spored basidia, globose, non-diverticulate caulocystidia, and growth on leaves of Araucaria angustifolia ( Maas Geesteranus and de Meijer 1997) . No other known species from tropical habitats growing on coconut debris show close similarity to M. longinqua .

Pairwise comparisons of aligned, overlapping ITS sequences of M. longinqua (BAP 648) with the top ten BLAST results indicate 94.2% similar to M. cyanorhiza Quél. (JF908385) and 93.6% similarity to M. stylobates (Pers.) P. Kumm. (JF908439). In the ITS phylogeny ( Fig. 2), M. longinqua belongs in a heterogeneous clade with members of sects. Exornatae , Polyadelphia , Granuliferae , Longisetae and Sacchariferae .

Figures

FIGURE 17. Basidiomata of Mycena longinqua (BAP 648, Holotype). Scale bar = 1 mm.

FIGURE 18. Mycenalonginqua (BAP 648,Holotype).a.Basidiospores.b.Basidia.c.Cheilocystidia.d.Pileipellishyphae.e.Caulocystidia. Scale bar = 10 μm.