Marasmius roseus J. S. Oliveira 2022, sp. nov.
Creators: name: S, Jadson José
name: Oliveira, ouza de
name: Capelari, Marina
name: Margaritescu, Simona
name: Moncalvo, Jean-Marc
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Agaricales
Marasmiaceae
Marasmius
Marasmius roseus

description: Marasmius roseus J.S. Oliveira, sp. nov.
(Figs 15A; 16; 17)
Differs from M. pallescens in having longer basidiospores (12-20 µm vs 11-17 µm) and pleurocystidia (37.5-75.5 µm vs 32-43 µm); from M. pulcherripes also in the longer basidiospores (12-20 µm vs 11-15 µm), shorter setulae on the pileipellis broom cells (up to 4 µm vs up to 10 µm) and is devoid of the peculiar red stipe apex and inner extremities of the lamellae; from M. rubicundus (Singer) J.S. Oliveira, stat. nov. mainly in having smaller basidiospores, 12-20 × 3-4 µm (xm = 16.3 [± 2.4] × 3.6 [± 0.3] µm) vs (15.4-)16.2- 21.7(-22) × 2.7-4.7(-5) µm (xmm = 19 [± 0.5] × 3.8 [± 0.2] µm); differs from all in the peculiar dimorphic Siccus-type broom cells in the pileipellis: 1) thick-walled, with pale chestnut lilac lumen, setulae apical, short, often coarse; 2) in transition to Rotalis-type broom cells, thin-walled.
HOLOTYPE. — Brazil. São Paulo State, São Paulo City, Parque Estadual das Fontes do Ipiranga, 3.III.2011, J.J.S. Oliveira & F. Karstedt JO352 (holo-, SP [SP 445510]!).
ETYMOLOGY. — Based on the rose pileus.
MYCOBANK. — MB 842538.
HABIT AND SUBSTRATE. — Marasmioid (Figs15B; 16A), gregarious, on dead eudicotyledonous sticks in the forest litter.
DESCRIPTION
Pileus (Figs 15B; 16A)
2-21 mm diam., convex, orbicular, sulcate to deeply sulcate, center flat, somewhat wrinkled when mature, margin decurved to plane, edge entire to slightly crenate; grayish pink to lilac (N 40 Y 10 M 60), becoming pale pink or rose (N 40 Y 20 M 50), center purple or dark pink (N 90 Y 00 M 80); membranous, context thin (<1 mm); glabrous, dry, dull to semi translucent, subvelutinous, non-hygrophanous.
Lamellae (Figs 15B; 16A)
Free to adnate, distant, L = 12, equal, simple, l = 0(-1), opaque, smooth, whitish pink (N 00 Y 20 M 20), edge even, non-marginate, interlamellar hymenium concolorous with the pileus.
Stipe (Figs 15B; 16A)
8-40 × 0.3-0.7 mm, central, filiform, thin, equal, with circular caliber, chitinous, hollow; apex concolorous with the lamellae, becoming dark brown to almost black elsewhere, glabrous, smooth, with a silky bright; with a scarce, cream, tomentose basal mycelium.
Odor
Not distinctive.
Basidiospores (Fig. 16B)
12-20 × 3-4 µm (xm = 16.3 [± 2.4] × 3.6 [± 0.3] µm, Qm = 4.5 [± 0.6], n / s = 32/1), oblong, widely variable in length, clavate to subfusoid, smooth, hyaline, thin-walled, inamyloid.
Basidia
Not observed.
Basidioles (Fig. 16C)
17.5-26.3 × 5.4-8.8 µm, cylindrical to clavate, sometimes tapering toward the apex, smooth, hyaline, thin-walled, inamyloid.
Pleurocystidia (Fig. 16D)
37.5-75.5 × 6.3-10.6 µm, abundant, conspicuously projecting, cylindrical, clavate, sometimes ventricose, generally with tapered apex, or capitate, some worm-like to irregular in outline, apex easily breakable, smooth, slightly fuscous, yellowish, thin-walled, refractive, inamyloid.
Cheilocystidia (Fig. 16E)
In form of Siccus-type broom cells, some apparently in transition to Rotalis-type similar to the broom cells of the kind 2 in the pileipellis; main body 11.3-17.5 × 6.3-10 µm, clavate to pyriform, rarely cylindrical to ventricose, thin-walled, hyaline; setulae apical to little divergent to the laterals, erect, generally short, 0.6-3.8 × 0.5-1 µm, digitiform or verruciform, simple or branched, solid, pale brown, regular to somewhat irregular in outline, apex obtuse to slightly acute.
Lamellar trama
Dextrinoid, irregular, interwoven, hyphae cylindrical, 1.3- 7.5 µm diam., regular or irregular in outline, branched, smooth, hyaline, thin-walled.
Pileus trama
Similar to the lamellar trama, hyphae 2-7 µm diam.
Pileipellis
Hymeniform, mottled, composed of Siccus-type broom cells, of two kinds: 1) abundant at the pileus center and abruptly less frequent from the mid disc to the marginal zone (Fig. 17A); main body 5-17.5 × 7.5-11.3 µm, pyriform, turbinate to subclavate, sometimes apically flattened, thick-walled especially at the apex, with pale chestnut lilac lumen; setulae apical, erect, short, 1.3-4 × 0.8-1.3 µm, digitiform to verruciform, or vesiculose, sometimes branched, often coarse, regular to irregular in outline, solid, hyaline to pale brown, apex obtuse; and 2) more numerous at the mid disc and predominant at the marginal zone (Fig. 17B), some apparently in transition to Rotalis-type broom cells, rarely almost devoid of apical diverticula; main body 8.8-20 × 5.6-12.5 µm, clavate, turbinate, ventricose to subpyriform, walls very thin, completely hyaline, difficult to be individualized; setulae apical and frequently divergent to the laterals, erect, generally short, 0.3-2.5(-4) × (0.2-)0.5-1 µm, vesiculose, verruciform to digitiform, solid, pale brown, apex obtuse and rounded, or irregular.
Stipe trama
Dextrinoid, especially in the internal hyphae, cortical hyphae parallel, cylindrical, regular in outline, 2.5-8.8 µm diam., wrinkled, dark brown, walls not clearly thick, or thin-walled; internal hyphae hyaline, 2.5-10 µm diam., thin-walled.
Clamp connections
Present in all tissues, except in the cortical hyphae of the stipe.
REMARKS
Marasmius roseus J.S. Oliveira, sp.nov. differs from M. haematocephalus mainly by having pale purplish pink to pale lilac pileus center, then pink or rose from the mid disc to the margin, by having widely variable length of basidiospores (12-20 µm), and by having a mottled pileipellis with two kinds of Siccus-type broom cells (one apparently in transition to Rotalis-type). It is 2.2 % and 0.5 % dissimilar to M. haematocephalus s. str. (JO533) in the nrITS and nrLSU, respectively.
Marasmius roseus is morphologically somewhat similar to M. pallescens sensu Singer (1976), especially in the light lilac pileus form (Dennis 1961). Singer (1976) also observed a mottled pileipellis in M. pallescens due to some broom cells with darker melleous apical setulae among paler broom cells. However, M. pallescens has shorter basidiospores (11- 17 µm) and smaller pleurocystidia (32-43 × 10-15.2 µm). Marasmius roseus J.S. Oliveira, sp. nov. is also very close to M. rubicundus (Singer) J.S. Oliveira, stat. nov. (next taxon) in the pileus pigmentation, but this later varies more widely from pale red to rose, ruby pink, even purplish pileus while has basidiospores less variable in length and larger in average (xmm = 18.8 [± 1.3] × 3.8 [± 0.2] µm), and non-mottled pileipellis composed of regular Siccus-type broom cells.
Marasmius pulcherripes is similar especially by having similar pileus pigmentation and mottled pileipellis due to thickwalled, purplish broom cells among more regular ones in the pileipellis (Gilliam 1976; Antonín et al. 2012). However, it differs from M. roseus J.S. Oliveira, sp. nov. mainly by having shorter basidiospores (11-15 µm) and longer apical setulae (up to 10 µm) on the broom cells of the pileipellis beside the typical stipe pigmentation. None of the heterotypic synonyms under M. haematocephalus listed in Singer (1976) nor their varieties seem conspecific with M. roseus J.S. Oliveira, sp. nov. Marasmius haematocephalus var. transiens Singer also has basidiospores largely variable in size ([12.5-]13-22 × 3.5-4.5 µm), but the pileus (3-12 mm diam.) color is completely different with no similar cells in the pileipellis (Singer 1965, 1976).
description: Published as part of S, Jadson José, Oliveira, ouza de, Capelari, Marina, Margaritescu, Simona & Moncalvo, Jean-Marc, 2022, Disentangling cryptic species in the Marasmius haematocephalus (Mont.) Fr. and M. siccus (Schwein.) Fr. species complexes (Agaricales, Basidiomycota), pp. 91-137 in Cryptogamie, Mycologie 20 (5) on pages 118-120, DOI: 10.5252/cryptogamie-mycologie2022v43a5, http://zenodo.org/record/7829356