Marasmius insolitus Kiyashko & E.F. Malysheva, 2014

Kiyashko, Anna A., Malysheva, Ekaterina F., Antonín, Vladimír, Svetasheva, Tatiana Yu. & Bulakh, Eugenia M., 2014, Fungi of the Russian Far East 2. New species and new records of Marasmius and Cryptomarasmius (Basidiomycota), Phytotaxa 186 (1), pp. 1-28 : 14-16

Marasmius insolitus Kiyashko & E.F. Malysheva , sp. nov. ( Fig. 2B–C , Fig. 6)

MycoBank 807121

Characterized by a pale coloured yellowish, non-sulcate pileus and a pruinose stipe, basidiospores on average 11 × 4 µm in size, cheilo- and pleurocystidia consisting of Siccus-type broom cells, dimorphic caulocystidia, and by the presence of distinctive spider-like thick-walled cells with more than 30 µm long setulae in the pileipellis.

Holotype: RUSSIAN FEDERATION. Primorsky Territory: Kedrovaya Pad’ State Nature Reserve, watershed of the Ananjevka and Gryaznaya rivers, mixed forest with dominance of broadleaved trees, on fallen leaves, 01 Sept. 2011, E. Malysheva ( LE 289497!), GenBank KF774162 for ITS, KF896248 for nrLSU.

Pileus 10–18 mm in diam., hemispherical or convex with low broad umbo; not hygrophanous, not striate, smooth (wrinkled when dried in herbarium), slightly pruinose, dull; pale yellow (3 A 3) with slightly darker greyish yellow (4 B 5) centre; margin slightly inflexed. Lamellae adnexed, close (appr. 27 reaching the stipe) with 2–3 series of lamellulae, narrow (<4 mm), whitish or cream, with concolorous serrulate edge. Stipe 25–65 × 2–3 mm, central, cylindrical, hollow, entirely pruinose, concolorous with lamellae in upper part, greyish yellow (4 B 5) at base, with well-developed whitish basal tomentum. Odour and taste indistinct.

Basidiospores (8.4)10.0–12.5 × 3.6–4.7(5.2) µm, χ m = 11.2±0.7 × 4.15±0.3 μm, Q = (1.8)2.4–2.9, Q m = 2.6±0.1, n = 21, s = 2; ellipsoid to ellipsoid-fusoid, smooth, thin-walled, hyaline, inamyloid. Basidia 20.8–26.8 × 5.2–5.9 µm, 4- spored, clavate. Cheilocystidia numerous, consisting of thick-walled Siccus - type broom cells, main body subcylindrical to clavate, sometimes irregular in outline or lobed in upper part, (11.0)13.5–31.2 × 4.5–6.5(10.0) μm, hyaline, with cylindrical to conical, often tortuous, subacute, thick-walled apical projections up to 17 μm long. Pleurocystidia numerous, similar to cheilocystidia in shape and size, arising from hymenium. Pileipellis a hymeniderm composed of two types of cells: a) Siccus - type broom cells with hyaline, thin- to thick-walled, clavate to subcylindrical or irregular, often lobed main body, 13.0–24.7 × 6.5–10.5 μm, with cylindrical to conical, tortuous to nodulose, subacute apical projections up to 15 μm long; b) spider-like thick-walled cells with short, irregular-shaped, often tuberous main body and long, acute thick-walled setulae (3‒7 per cell) more than 30 μm long. Stipitipellis a cutis of parallel, cylindrical or slightly inflated thin-walled hyphae. Caulocystidia present, numerous, varying in shape: a) thick-walled elements with long, acute, branched setulae, 24–45 × 5–11 µm, main body polymorphic, sometimes reduced, cylindrical, subclavate, forked to irregular, often tuberous, weakly dextrinoid, hyaline or with yellowish refractive content; b) inamyloid or only weakly dextrinoid scarce broom cells with projections up to 13 μm; c) thin-walled, inamyloid, non-setulose cells, obtuse, polymorphic, clavate or irregular in outline, hyaline, 21.5–41.5 × 5.2–11.5 µm, in clusters. Clamp connections present in all tissues.

FIGURE. Microscopic features of Marasmius insolitus sp. nov. ( LE 289497, 289498). A. Spores. B. Basidium. C. Cheilocystidia. D. Pleurocystidia. E. Spider-like long-setulose cell from pileipellis. F. Pileipellis cells. G. Long-setulose caulocystidia. H. Non-setulose caulocystidia.―Scale bar = 10 μm.

Etymology: From the Latin word insolitus = unconventional, referring to the presence of unusual spider-like elements in pileipellis and stipitipellis.

Habitat and distribution: Solitary on fallen leaves in mixed forest ( Acer , Quercus , Carpinus , Abies ), Manchurian mountain range.

Additional specimen examined (paratype): RUSSIAN FEDERATION. Primorsky Territory : KPNR , watershed of the Ananjevka and Gryaznaya rivers, mixed forest with dominance of broadleaved trees, on fallen leaves, 01 Sept. 2011, N . Psurtseva ( LE 289498!) .

Observations: This new species is characterized by a well-developed stipe vesture composed of setulose and nonsetulose cells and Siccus - type pleurocystidia. This combination of features causes some difficulties to identify the series in sect. Sicci , to which it belongs. According to Desjardin (1989), ser. Atrorubentes includes taxa with smooth, obtuse or acuminate, sometimes setoid but not Siccus - type caulocystidia, typically without pleurocystidia. Well-developed but non-setulose pleurocystidia are the main diagnostic feature of ser. Haematocephali. In this series, caulocystidia are present or absent; if present, then the Siccus - type elements are never cylindrical, clavate or acuminate. The new species possesses intermediary features between these two series. For now we consider it better to accommodate this taxon into ser. Atrorubentes.

There are a few species in ser. Atrorubentes with dimorphic caulocystidia in East Asia. One of them, Marasmius luteolus Berk. & M.A. Curtis , differs in having a bright, orange-tinged, striate to sulcate, thin pileus up to 42 mm in diam., as well as in the absence of the spider-like long setulose cells on the pileus and stipe surfaces ( Wannathes et al. 2009b). The genetic distance between the ITS sequences of the new species and M. luteolus is rather high (8.4%). Marasmius jasminodorus Wannathes, Desjardin & Lumyong is characterized by a dark reddish brown rugulose pileus, slightly smaller basidiospores (χ m = 10.1±0.5 × 3.6±0.3 μm vs. χ m = 11.2±0.7 × 4.15±0.3 μm), absence of spider-like long setulose cells as well as the presence of a specific fragrant odour ( Wannathes et al. 2009b). Marasmius araucariae Singer var. araucariae and M. araucariae var. siccipes Desjardin, Retn. & E. Horak both have a rugulose or sulcate reddish brown to dark brown pileus, cream or brownish tinged lamellae, no pleurocystidia, and spider-like structures in the pileipellis and stipitipellis. It should be noted that the type variety of M. araucariae has no Siccus - type caulocystidia, while M. araucariae var. siccipes forms numerous Siccus - type broom cells on the stipe surface ( Wannathes et al. 2009b). Marasmius ochroleucus is macroscopically similar to other membes of ser. Atrorubentes and has only non-setulose, obtuse caulocystidia and can be easily distinguished from M. insolitus by the absence of pleurocystidia. Marasmius iras Y.S. Tan , M. inthanonensis Wannathes, Desjardin & Lumyong and M. xestocephalus Singer have appreciably larger basidiospore dimensions, not overlapping those of M. insolitus . Also these species form non-setulose caulocystidia. Marasmius ochropoides Y.S.Tan & Desjardin differs in having an orange-tinged pileus and cheilocystidia with 2–4 apical setulae per cell as well as in the absence of pleurocystidia and in having only Siccus - type caulocystidia ( Tan et al. 2009).

In ser. Haematocephali, Marasmius sullivantii Montagne from North America is somewhat similar due to the nature of its stipe vesture but can be distinguished by the reddish brown pileus, smaller basidiospores (χ m = 7.6±0.3 × 3.6±0.1 μm) and non-setulose pleurocystidia ( Desjardin 1989). Siccus - type pleurocystidia are also found in Marasmius setulosifolius Singer from the Neotropics. The latter differs from the new species by having a rusty coloured sulcate pileus and the absence of non-setulose caulocystidia ( Singer 1976).

Marasmius araneocephalus Wannathes, Desjardin & Lumyong of ser. Spinulosi possesses spider-like cells with apical setulae (30–70 μm long) which are very similar to those of M. insolitus . However, M. araneocephalus has a very different habit, distinctly smaller basidiospores (χ m = 6.6±0.6 × 3.9±0.3 μm vs χ m = 11.2±0.7 × 4.15±0.3 μm) and typical hymenial setae ( Wannathes et al. 2009b).

Figures

FIGURE 2. Mature basidiocarps. A. Marasmius macrocystidiosus sp. nov. (LE 295996). B–C. Marasmius insolitus sp. nov. (LE 289497). D. Marasmius cohaerens var. mandshuricus var. nov. (LE 295987). E. Marasmius cf. ochroleucus (LE 295978). F. Cryptomarasmius aucubae (LE 289499). G. Marasmius occultatiformis (LE 295976). Scale bar = 1 cm.