Marasmius subtropicus A.K. Dutta & K. Acharya, sp. nov.
Index Fungorum number: IF 557846; MycoBank number: MB 557846; Facesoffungi number: FoF 07865; Figs. 1, 2
Etymology – ‘subtropicus’ refers to the subtropical geographic region from where the taxon was collected.
Holotype – CUH AM226
Pileus 20–58 mm diam., convex when young, becoming broadly convex to plano-convex with a small umbo at maturity, margin often upturned, smooth to minutely pubescent, semi moist to dry, disc light brown (6D6) to brown (6E6-8), slightly rugulose, orange (5A6-7) to brownish yellow (5C7) towards middle, light yellow (1A5) to greyish yellow (1B6-7, 2-3B5, 4B6) towards extreme margin, on drying turns orange (6A7, 6B8) to deep orange (6A8) or brownish orange (6C8) with brown (6E7-8) disc, translucent when young, becoming sulcate to often rimos at maturity, context thin, cream. Lamellae 2–3 mm broad, adnexed, distant to subdistant (L=19–22, l=4–5), white (1A1) to cream, strongly intervenose, often forked from the middle, concolorous. Stipe 25–64×2–4 mm, central, cylindrical, noninsititious, equal with slightly broader at base (up to 6 mm), often cleft towards middle, brownish yellow (5C7) to orange or deep orange (6A8) with paler to cream towards apex, glabrous, hollow, basal mycelia well developed, orange. Odour and taste indistinctive. Basidiospores (7–)9–10.5(–11.5)×(4–)6–7(–7.2) μm (x̅ =10×6.5 μm, n=30), Q=1.2–1.7 μm (x̅ =1.5 μm, n=30), ellipsoid, hyaline, inamyloid, thinwalled. Basidia 25–29×5–6.5(–7.5) μm, clavate, hyaline, thin-walled, 4-spored, sterigmata 2.5–4 μm long. Basidioles (21.5–)28–31(–36)×(5–)6–6.5(–7.5) μm, cylindrical to clavate or fusoid, hyaline, thin-walled. Pleurocystidia absent. Lamellae-edge sterile, with well-developed cystidia. Cheilocystidia common, composed of Siccus-type broom cells; main body (10–)11–14(–18)×(3.5–)4.5–6(–8.5) μm, cylindrical to clavate or irregular in outline, often branched, hyaline, inamyloid, thin- to thick-walled; apical setulae (2.5–)6.5–7.5(–10.5) μm long, cylindrical, hyaline to pale yellow, inamyloid, acute to subacute, thick-walled. Pileipellis hymeniform, composed of Siccus-type of broom cell; main body (10.5–)14–15(–18)×(5.5–)7–9(–11) μm, cylindrical to clavate, hyaline, inamyloid, thin- to thick-walled; apical setulae (3.5–)6–8(–10.5) μm long, cylindrical, yellowish to light brown, inamyloid, acute to subacute, thick-walled. Pileus trama hyphae interwoven, (4–)7–8(–11) μm broad, cylindrical to often inflated, hyaline, dextrinoid, thin-walled, non-gelatinous. Lamellae trama hyphae interwoven, 3.5–7(–7.5) μm broad, cylindrical, hyaline, dextrinoid, thin-walled, non-gelatinous. Stipitipellis hyphae 3.5–4.5(–5.5) μm broad, parallel to subparallel, cylindrical, thin-walled, pale yellowish in KOH, nongelatinous. Stipe trama hyphae 7–8(–9.5) μm broad, parallel, cylindrical, hyaline, dextrinoid, thin- to moderately thick-walled, nongelatinous. Caulocystidia absent. Clamp-connections present in all the tissues.
Material examined: INDIA, West Bengal, South-24-Parganas district, Lakshmikantapur, 22°06′35.9″ N 88°19′12.7″ E, 6 msl, among decomposed leaf litter under Cocos nucifera tree, 26 June 2015, J. Sarkar (CUH AM226, holotype); South-24-Parganas district, Baruipur, 22°21′35.3″ N 88°27′13.6″ E, 9 msl, among decomposed leaf litter, 23 June 2016, A.K. Dutta (CUH AM706).
GenBank numbers: ITS = MF189061, MF189062, LSU=MT254998, MT255000.
Notes: Distinctive feature of the specimen includes a medium to large, convex to plano-convex pileus coloured
orange to brownish yellow with light brown to brown towards central small umbo, distant to subdistant, strongly intervenose, white lamellae, a central, non-insititious, glabrous, brownish yellow to orange or deep orange stipe with well-developed basal mycelia coloured orange, ellipsoid basidiospores with a mean of 10× 6.5 μm (Q mean 1.5), presence of Siccus-type cheilocystidia with apical setulae measuring 2.5–10.5 μm, and absence of pleurocystidia and caulocystidia. All these combination features undoubtedly place the present taxon to ser. Leonini of the sect. Sicci (Desjardin et al. 2000).
Figure 1 – Field pictures of the basidiomata. a, b Marasmius subtropicus (CUH AM226, holotype), habitats of basidiomata and lamellae showing intervenose nature. Scale bars: a, b=10 mm
Figure 2 – Marasmius subtropicus (CUH AM226, holotype). a Basidiospores. b basidia. c Siccus-type cheilocystidia. d Siccus-type pileipellis cells. Scale bars: a–d=5 μm