Marasmius tricystidiatus Ramírez & Niveiro, 2021

Ramírez, Natalia A., Niveiro, Nicolás, Salvador-Montoya, Carlos A., Motta, Fátima Piris Da, Pérez, M. Laura & Popoff, Orlando F., 2021, Marasmius tricystidiatus sp. nov. (Agaricales, Marasmiaceae) and its morphological and phylogenetic relationship with Marasmius jalapensis, Phytotaxa 494 (1), pp. 59-74 : 65-66

Marasmius tricystidiatus Ramírez & Niveiro sp. nov. Figs. 3–4 , 6A , 7A–B

Mycobank: MB835548, Facesoffungi number: FoF08149.

Holotype:— ARGENTINA. Chaco: Primero de Mayo, Reserva Natural Educativa Colonia Benítez , 27°26ʹ19.20ʺS, 058°50ʹ51,39ʺW, 22 March 2016, N.A. Ramírez & N. Niveiro, NR 100 ( CTES 0568258 ). GenBank MT441866 and MT436267 ( ITS and LSU, Holotype).

Diagnosis:—Basidiomata medium-sized; pileus yellowish, slightly sulcate; basidiospores cylindric to subfusiform, 6.5–11.8 × 2.8–4.8 µm; setae in all dermal tissues; cheilocystidia of three types: Siccus - type broom cells, setae and transitional elements between the formers.

Etymology:—Refers to the presence of three types of cheilocystidia.

Description:— Basidiomata marasmioid. Pileus 15–43 mm diam., convex to plano-convex, smooth, margin entire, weakly sulcate, yellowish white (1A2) to pale yellow (1A3) with greyish yellow (2B3) centre when young, with more intense colors when mature, dull yellow (3B3) to light yellow (3A4), or greyish yellow (4B4) with light orange (5A5) center, or in some cases brown (6D7); surface dry, dull, subvelutinous, non-hygrophanous. Context thin, less than 1 mm, membranous, yellowish white (1A2); odor and taste not tested. Lamellae adnexed, subventricose, close to subclose, L= 28–36, regular, l= 2–3 tiers, densely pubescent under lens, yellowish white (1A2) to pale yellow (3A3); margin entire, concolorous. Stipe 48–68 × 0.8–1.5 mm, central, cylindrical, equal, hollow, cartilaginous; surface dull, pilose, denser at the apex, dark brown (7F7) to brown (7E8), paler towards the apex, light brown (6D8) to greyish orange (5B5); tomentose basal mycelium, greyish yellow (4B4). Spore print whitish (4A1–4A2).

Basidiospores 6.5–11.8 × 2.8–4.8 µm, x = 9.2 × 3.4; Q= 2.1–3.2; Q x = 2.7; n= 25; N=2; cylindrical to subfusiform, smooth, hyaline, thin-walled, inamyloid. Basidia 22–26 × 4.5–7.5 µm, clavate, smooth, hyaline, 4-spored, thin-walled. Pleurosetae 40–73 × 6–19.5 µm, lanceolate, smooth, with acuminate apex, rarely mucronate, thick-walled (1.5–2.5 µm), chestnut to golden melleous, arising from the hymenophoral trama, abundant. Cheilocystidia of three types, viz., cheilosetae, similar to pleurosetae, 24–54 × 6.5–11 µm, lanceolate, thick-walled (1–2.5 µm), with acute ápex; Siccus - type broom cells, main body 18–28 × 9–11.5 µm, clavate, thin-to thick-walled, 0.5–1.5 µm, with apical setulae up to 9 µm long; and transitional elements between setae (type a) and broom cells (type b), main body 27.5–37.5 × 7–12 µm, with 2–7 apical setulae up to 24.5 µm long, thick-walled (1–2 µm). Hymenophoral trama strongly dextrinoid, subregular, formed by hyaline hyphae, cylindrical, smooth, thin-walled. Pileipellis hymeniform, composed of 3 types of cells, viz., Siccus - type broom cells, main body 14–23 × 5–10 µm, with apical setulae up to 9.5 µm long, thin-to slightly thick-walled; pileosetae, scattered, 53–62 × 6–7 µm, acicular, simple, smooth, with acuminate apex, thick-walled (up to 1.5 µm); and transitional elements between setae and broom cells, main body 25–35 × 3–9.5 µm, branched, smooth, thick-walled (1–1.5 µm), with 2–5 apical setulae up to 24 µm long, with acuminate apex. Stipitipellis made up of thinwalled, elongated hyphae, hyaline, parallel, cylindrical, dextrinoid. Caulocystidia composed of 2 types of cells, viz., caulosetae, 39.5–110.5 × 5–11.5 µm, simple, with somewhat widened base and acute apex, thick-walled (0.5–2 µm), chestnut to brown, abundant; and transitional elements between setae and broom cells, main body 26.5–49 × 8.5–12.5 µm, branched, with 2–3 apical setulae up to 40 µm, with acute apex, thick-walled (0.5–1.5 µm), chestnut to brown. Clamp connections present.

Ecology and distribution:—marasmioid, gregarious, growing on rotting fallen twigs of unidentified eudicot. Argentina and Colombia.

Specimens studied:— ARGENTINA. Chaco: Primero de Mayo, Reserva Natural Educativa Colonia Benítez , 27°26ʹ19.20ʺS, 058°50ʹ51,39ʺW, 22 March 2016, N.A. Ramírez & N. Niveiro, NR 101 ( CTES 0568259 !) . Id. NR 102 ( CTES 0568260 !) . Ibid. 11 November 2013, N. Niveiro & N.A. Ramírez, CB T6-02 ( CTES 0568170 !) . Ibid. 7 March 2014, N. A. Ramírez, N. Niveiro & A.A. Avalos, CB 19-44 ( CTES 0568169 !) . COLOMBIA. Antioquia: Sonson , ± 10 km NE of Sonson, along road to Narino, 16 November 1986, R.E. Halling 5030 (NY 02506198!) .

Comments:— Marasmius tricystidiatus is characterized by its yellowish and slightly sulcate pileus, medium-sized basidiomata, setae in all tissues and cheilocystidia of three types, viz., Siccus - type broom cells, setae, and transitional elements. It resembles M. jalapensis in color and the presence of setoid cystidia in all tissues, but M. jalapensis mainly differs in having broader basidiospores (3.5–5.5 µm) and only cheilosetae on the edge of the lamellae. Marasmius tricystidiatus can be easily confused with M. venezuelanus Dennis (1961: 97) (described from Colombia and Venezuela) due to the similar pileus coloration and the presence of setoid cystidia on the lamellae edges. Nevertheless, M. venezuelanus has a smaller pileus (20–30 mm diam.) and basidiospores (6–9 × 3–3.5 µm), along with smooth cells in the pileipellis, broom cells and setae ( Singer 1976; Pegler 1977). Another similar species is M. delectans Morgan (1905: 206) described from Canada and USA, but it has a glabrous stipe, smaller basidiospores (6–8.8 × 3.4–4.4 µm) and pleurocystidia (24–65 × 5.5–8 µm) ( Desjardin 1989). In the micromorphology, M. tricystidiatus is similar to M. cohaerens ( Persoon 1801: 306) Cooke & Quélet (1878: 153) , the latter widely known in the Northern Hemisphere. However, M. cohaerens has a smaller (10–26 mm diam.) and a darker pileus [dark brown (7F5–7) to dark reddish brown (8F5–7)] ( Singer 1976; Desjardin 1989). Another similar species to M. tricystidiatus is M. coarctatus Wannathes, Desjardin & Lumyong (2009: 251) , especially in the macro features of the lamellae and stipe, composition of the pileipellis, and presence of setae in all tissues. However, M. coarctatus differs by having a paler and smaller pileus (10–27 mm diam.), shorter basidiospores [6–8(–10) µm, x = 6.6 ± 0.4], narrower cheilosetae (4–6 μm), and caulocystidia in the form of the typical Siccus - type broom cells, in addition to the absence of (or seldom present) pleurosetae, and intermediate cheilocystidia between setae and broom cells ( Wannathes et al. 2009).

Marasmius tricystidiatus can be compared to M. diversus C.L. Grace, Desjardin & B.A. Perry (2019: 72) from Africa and M. coklatus Desjardin, Retnowati & E. Horak (2000: 146) from Indonesia and Thailand. Marasmius diversus differs in forming a darker and smaller pileus (15–24 mm diam.), shorter stipe (30–38 mm), longer basidiospores (14–16 µm), smaller cheilocystidia (4–13.6 × 3–7.2 μm), the presence of caulosetae (12–60 × 5.8–8.2 μm) and cylindrical to substrangulate pleurocystidia, and absence of pleurosetae ( Grace et al. 2019). In turn, M. coklatus can be distinguished from the new species in having a darker pileus with a distinctly rugulose-undulate disc, remote to distant lamellae (L=10–15, l=1–2 tiers), a more robust stipe (3–5 mm) which is pruinose due to the presence of broom cells in the stipitipellis, broader basidiospores (4.5–6 μm), and by the presence of Siccus - type pleurocystidia ( Desjardin et al. 2000, Wannathes et al. 2009). Finally, the new species resembles M. nummularius Berkeley & Broome (1873: 33) in the pileus pigmentation, composition of the pileipellis, and cheilocystidia in the form of Siccus - type broom cells and caulosetae. However, M. tricystidiatus differs from M. nummularius in having a smaller pileus (2–20 mm diam.), shorter stipe (20–48 mm), subdistant lamellae (L= 12–18), larger basidiospores (12–15 μm), caulocystidia in the form of Siccus - type broom cells, and absence of pleurosetae, cheilosetae and intermediate cheilocystidia between the setae and broom cells ( Desjardin et al. 2000, Wannathes et al. 2009, Shay et al. 2017).

Figures

FIGURE 3. Marasmius tricystidiatus (NR 100). General aspect and habit. Scale bar = 15 mm. Photograph by N.A. Ramírez.

FIGURE 4. Micromorphological features of Marasmius tricystidiatus (NR 100). A. Basidiospores. B. Basidia. C. Pleurosetae. D. Cheilosetae. E. Siccus-type broom cells cheilocystidia. F. Transitional elements between setae and broom cells on the lamellae edge. G. Siccus-type broom cells of the pileipellis. H. Pileosetae and transitional elements in the pileipellis. I. Caulosetae and transitional elements in the stipitipellis. Scale bars = 10 µm. Drawings by N.A. Ramírez.

FIGURE 6. SEM micrographs of basidiospores. A. Marasmius tricystidiatus (NR 100). B. Marasmius jalapensis (414F). C. Marasmius jalapensis (type material, Murrill & Murrill 84). D. Uganda specimen (K 134432). Scale bars = 2 µm. Photos by N.A. Ramírez.

FIGURE 7. SEM micrographs of cheilocystidia. A–B. Marasmius tricystidiatus (NR 100). C. Marasmius jalapensis (type material, Murrill & Murrill 84). D. Marasmius jalapensis (414F). E–F. Uganda specimen (K 134432). Scale bars A–B = 5 µm, C–F = 10 µm. Photos by N.A. Ramírez.