Marasmius calvocystidiatus sp. nov. and M. horridulus (Marasmiaceae): characterization of two unusual species from central Amazonia Author Komura, Dirce L. Instituto Nacional de Pesquisas da Amazônia (INPA), Dept. of Biodiversity (CBio) C. P. 478, 69011 - 970 Manaus, Amazonas, Brazil. Author De Oliveira, Jadson J. S. Depart. of Natural History, Royal Ontario Museum, and Author Moncalvo, Jean-Marc Depart. of Natural History, Royal Ontario Museum, and & Dept. of Ecology and Evolutionary Biology, University of Toronto, Canada Author Margaritescu, Simona Depart. of Natural History, Royal Ontario Museum, and Author Zartman, Charles E. Instituto Nacional de Pesquisas da Amazônia (INPA), Dept. of Biodiversity (CBio) C. P. 478, 69011 - 970 Manaus, Amazonas, Brazil. text Phytotaxa 2016 2016-10-21 280 3 222 240 http://dx.doi.org/10.11646/phytotaxa.280.3.2 journal article 10.11646/phytotaxa.280.3.2 1179-3163 13648937 Marasmius calvocystidiatus D.L.Komura & J.S.Oliveira , spec. nov. Figs. 2–4 MycoBank: MB818286 Etymology:—Refers to the smooth, ‘bald’ cystidia in the pileipellis. Holotype :— BRAZIL . Amazonas State : Manaus District , Estação Experimental de Manejo Florestal do INPA (ZF-2), 23 May 2013 , DLK1516 ( INPA !). Diagnosis:—Pileus convex to plane, papillate, chestnut brown to pale brown, glabrous, rigid. Lamellae collariate, L = 32–34, thick, pale golden. Stipe cylindrical, thin, insititious, glabrous, golden to reddish brown. Basidiospores 4.2– 5.2 × 2.6–3.9 μm. Trama dextrinoid. Cheilocystidia in form of Chrysochaetes - type broom cells. Pileipellis hymeniform to irregularly hymeniform, made up by smooth, thick-walled cells, sometimes lobed or having coarse excrescences. On dicotyledonous leaves in the litter. Barcode sequence:—ITS: GenBank KU170115 ( holotype , DLK1516). Description:— Pileus 2–4 mm diam., shallowly and broadly plano-convex reminiscent of ‘drum cymbals’, smooth to shallowly sulcate, center slightly depressed with a conspicuous, broad papilla, margin tenuously incurved to plane, rarely uplifted, edge bulky, thick, often with irregular outgrowths, finely appendiculate; surface glabrous, dry, dull; chestnut brown to pale brown (914809 to F2B068), some dark brown (40260B); consistence rigid, context thin (< 1 mm ). Lamellae collariate, forming a very developed collar tight on the stipe apex, close, L = 32–34, thick, slightly arched, hymenium somewhat pale golden (FADD7F) when young, lamellae face white to cream-colored (F7E6AD) when mature, marginate with edge swollen or broad, rigid, velutinous, slightly waxy, fawn yellow (DBAB76) to cream (F7EFB7) near the pileus edge and the collar, this later usually darker, brown (B88651). Stipe 10–14 × 0.5–0.8 mm , central, cylindrical, thin (not filiform or hair-like) abruptly thinner at the apex, terete to occasionally depressed, insititious, with broad, swollen base; surface smooth, glabrous, bright; horny or chitinous, flexible, hollow; apex whitish to cream, especially when young, restricted to the very apex when mature, golden brown (9E6815) to reddish brown (963A08) elsewhere, base generally darker, or bronze all over (B8860B) when dried. Rhizomorphs absent. Odour undetectable. Taste not observed. Basidiospores 4.2–5.2 × 2.6–3.9 μm [χ m = 4.6 (± 0.3) × 3.2 (± 0.4) μm; Q m = 1.5 (± 0.1); n = 15], obovoid to more properly short-oblong, subellipsoid to lacrimoid, smooth, hyaline, thin-walled, inamyloid. Basidia clavate, thin-walled, hyaline, inamyloid, 4–sterigmate. Basidioles cylindrical to clavate, or fusoid, 20 × 5 μm. Pleurocystidia absent. Cheilocystidia ochraceous, abundant, Chrysochaetes - type broom cells, somewhat similar to Siccus - type broom cells, but with short, coarse diverticula; main body 5–15 × 10–20 μm, mostly long-pedicellate, some clavate, pyriform, thick-walled, coppery brown, dextrinoid. Lamellae trama weakly dextrinoid, irregular, hyphae interwoven, thin-walled, hyaline, smooth. Pileus trama dextrinoid, irregular (including the trama of the bulky edge), hyphae similar to those of the lamellae trama, a little more irregular in outline, abundantly branched or with many sprouts. Pileipellis hymeniform to irregularly hymeniform, composed of smooth cells, main body 4–15 × 10–38 μm, thick-walled, ochraceous brown to coppery brown, generally golden in the lumen, mostly regular, clavate, pyriform, some long-pedicellate, deepened in the pileus trama, sometimes lobed or irregular in outline, or with some apical, coarse, solid, obtuse excrescences, flattened due to the very thick wall (2.5–4 μm). Stipe trama in parallel, compact, hyphae cylindrical, golden brown, thick-walled (especially in the stipe cortex). Stipitipellis without differentiated structures. Clamp connections present in all tissues, but not seen at the base of the cells of the pileipellis. FIGURE 2. Marasmius calvocystidiatus (DLK1516–holotype). A. Basidiomata on leaves. B. Collariate lamellae. C . Detail of the papillate pileus. D . Basidiomata. E. Detail of the collar. F. Base of stipe and initial stage of basidiomata growth (black arrow). Scale bars: A = 5 mm. B , C = 1.8 mm. D = 6 mm. E = 1 mm. F = 4 mm. Photos by D.L. Komura. Habit and habitat:—Marasmioid, gregarious, saprophytic on dicotyledonous leaves of the litter at Amazonian terra firme forest. Material examined and distribution:— BRAZIL . Amazonas State , Manaus , Estação Experimental de Manejo Florestal do INPA (ZF-2), 18 April 2012 , J.M. Moncalvo , C.E. Zartman , D.L.Komura 307 ( INPA270734 !) ; 23 May 2013 , O.F. Menezes & D.L.Komura DLK1516 ( INPA259372 !) ; Pará State , Belterra , Floresta Nacional de Tapajós , 28 March 2014 , D.L. Komura , T . S. Cabral , I. R . Fonseca DLK1945 ( INPA259374 !) . Comments:—Despite the tiny size of the basidiomata, the brown to golden brown pigmentation of the pileus and stipe, and the later being cylindrical instead of filiform make it quite visible on decaying leaves of the litter. The basidiomata are tough, with a pileus more rigid than usually found in Marasmius species. The peculiar ‘drum cymbal’ pileus shape with a central, conspicuous papilla and the thick, close and collariate lamellae with a bulky edge to both the lamellae and the collar are obvious to the naked eye. This aspect of the lamellae is exactly the same found in Marasmius horridulus Singer , the next discussed taxon. In addition, M. calvocystidiatus presents a pileipellis formed by thick-walled, generally smooth cells, sometimes lobed or with apical, coarse excrescences; a completely unusual characteristic reported for the first time in species belonging to sect. Marasmius . These cells may be classified as Chrysochaetes - type cells, a third option of diverticulate cells not consistently used by Singer to define thick-walled, dextrinoid, unusual cells forming the pileipellis of many neotropical species ( Singer 1976 , Oliveira & Capelari 2016 ). No morphologically similar species were found which approximate M. calvocystidiatus . However, the newly described taxon shares some similarities with M. horridulus Singer as discussed below.