Marasmiellus minutisporus W. Lu, P. Nutaratat & J. Kumla, 2024

Lu, Wenhua, Nutaratat, Pumin, Kumla, Jaturong, Tibpromma, Saowaluck, Elgorban, Abdallah M., Karunarathna, Samantha C. & Suwannarach, Nakarin, 2024, Morphological and molecular identification of two new Marasmiellus species (Omphalotaceae, Agaricales) from Thailand, MycoKeys 109, pp. 31-48 : 31-48

Marasmiellus minutisporus W. Lu, P. Nutaratat & J. Kumla sp. nov.

Figs 2 C , 4

Type.

Thailand • Phatthalung Province, Khuan Khanun, Sago Palm ( Metroxylon sagu ) Forest , 7 ° 44 ' 02 " N, 99 ° 59 ' 47 " E; elevation 23 m; on decaying leaf and branches of deciduous tree; 6 September 2023; P. Nutaratat, P., Suwannarach & J. Kumla, ( CMUB 40054 ). GenBank accession numbers PP 889930 (nrITS) and PP 890011 (nrLSU) .

Etymology.

“ minutisporus ” refers to the small basidiospores of this species.

Diagnosis.

Differs from M. virgatocutis by the grayish-brown, convex, wrinkled pileus, longer pileus terminal, smaller elongated spores, and caulocystidia.

Macrostructures.

Basidiomata small-sized, marasmioid. Pileus 5–11 mm diam., thin, then expanding to applanate, with slightly inflexed, pulvinate when young, then deflexed, finally reflexed, and undulating margin, convex when age with depressed to umbilicate at disc., grayish brown (7 D 3), often with grey, brown, or dark gray (1 F 1) at the center, gray at the margin; often radially wrinkled, surface dry, slightly pruinose to tomentose under the lens. Lamellae distant, often more or less reduced, white to sordid beige with a concolorous overall, pruinose edge, I = 1–3, L = 13–16. Stipe 4–9 × 1 mm, cylindrical, often subbulbous at the base, off-white at the apex, fourth to fifth downward, and black or gray at the stipe base, entirely white pruinose, with basal tomentum. Context thin, soft, white, fistulose. Smell and taste none.

Microstructures.

Basidiospores (11) 12–15 (– 16) × (3) 4–5 μm (average = 14 × 4 μm), Q = (2.6) 2.8–4 (4.67), Qm = 3.5 ± 0.56, hyaline, inamyloid, cylindrical to fusiform, thin-walled. Basidia 25–28 × 7–9 μm, 4 - spored, sterigmata up to 5 μm long, clavate. Lamella edge sterile. Cheilocystidia 30–33 × 12–15 μm, somewhat clavate to subglobose, Pleurocystidia absent. Pileipellis a cutis made up of 4.0–10 μm wide, inamyloid, inflated or cylindrical hyphae, with scattered suberect to erect, thin-walled, smooth, sometimes terminal elements up to 61–99 × 3.0–10 μm, gradually tapering to an acute or rounded apex. Stipitipellis a cutis composed of cylindrical, inamyloid, parallel, slightly, not incrusted, smooth, thick-walled. Caulocystidia 25–50 × 4–5 μm, adpressed to erect, cylindrical, clavate, smooth, thin-walled. Clamp connection present.

Ecology and distribution.

Solitary to caespitose, in small groups growing on decaying leaves and twigs of deciduous trees. Known only from the type locality in southern Thailand.

Additional material examined.

Thailand • Phatthalung Province, Khuan Khanun, Sago Palm ( Metroxylon sagu ) Forest , 7 ° 44 ' 02 " N, 99 ° 59 ' 46 " E; elevation 23 m; on decaying leaf and twigs of deciduous tree; 7 September 2023; P. Nutaratat, N. Suwannarach & J. Kumla, ( CMUB 40055 ). GenBank accession numbers PP 889932 (nrITS) and PP 890012 (nrLSU) .

Figures

Figure 2. Habitat of Marasmiellus species in the present study A, B Marasmiellus thailandicus (CMUB 40052, holotype) C Marasmiellus minutisporus (CMUB 40054, holotype) D Marasmiellus scandens (CMUB 40056, new record). Scale bars: 10 mm (A – D).

Figure 4. Marasmiellus minutisporus (CMUB 40054, holotype) A basidiospores B basidia C cheilocystidia D elements of pileipellis E hyphae elements of stipe and caulocystidia. Scale bars: 5 μm (A); 10 μm (B – E).