Marasmius occultatiformis Antonín, R. Ryoo & H.D. Shin (2012: 616)

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 : 16-18

Marasmius occultatiformis Antonín, R. Ryoo & H.D. Shin (2012: 616) ( Fig. 2G , Fig. 7)

Pileus 8–15(20) mm in diam., hemispherical to convex with low obtuse umbo at first, then more or less plane, slightly rugulose or pitted at centre, margin inflexed, not or only slightly translucently striate, dry, not hygrophanous, pruinose, finely tomentose, cadmium orange, deep orange to brownish or reddish orange (5A8, 6A8-C8, 7B8-C8) at centre, slightly paler to light orange (5A5) towards margin. Lamellae adnexed or emarginate with small tooth, moderately close, whitish to cream, with concolorous or brownish orange edge. Stipe 25–45 × 1–2 mm, cylindrical, slightly broadened downward, cartilaginous, glabrous, lustrous, whitish at the top, reddish brown to dark brown below, basal tomentum sparse, whitish or yellowish. Odour and taste indistinct.

Basidiospores 6.5–10.8(11.0) × 3.1–4.8 µm, χ m = 8.3±1.0 × 4.0±0.4 µm, Q = (1.5)1.7–2.9 (3.7), Q m = 2.1±0.3, n = 10–20, s = 3 (mature specimens); smooth, ellipsoid-fusoid, slightly lacrimoid, hyaline, thin-walled, inamyloid. Basidia 2- and 4-spored (often both in a single basidiome), 20.6–31.1 × 6.8–7.7 µm, sparse. Cheilocystidia in the form of Siccus - type broom cells, (9.8)10.4–28.5 × 4.0–7.3 µm, clavate, (sub)cylindrical, sometimes wavy in outline, more or less thick-walled, with projections 3.1–15.0 µm, rarely up to 20 µm long, tortuous to nodulose, obtuse, thick-walled. One specimen ( LE 289489) also has scattered, smooth thin-walled elements, 13.0–15.5 × 3.8–6.8 µm in size, at the lamellae edge. Pleurocystidia absent. Pileipellis a hymeniderm composed of Siccus - type broom cells, (11.7)13.5–32.0 × 4.5–9.0(11.2) µm, clavate, subcylindrical, slightly to distinctly tortuous, sometimes lobed, more or less thin-walled at base, thick-walled at apex, mixed with scattered entirely thick-walled ones, projections predominantly 3.5–8.5 µm long, rarely up to 20 µm, tortuous to nodulose, thick-walled; all thick-walled parts yellow-brown in KOH. Stipitipellis a cutis of cylindrical, parallel, slightly thick-walled, minutely incrusted hyphae, with brown walls in KOH. Caulocystidia absent. One specimen ( LE 295974) has sparse thick-walled branched elements at the apex of the stipe, but this feature does not seem to be typical of this species. Clamp connections present in all tissues .

FIGURE. Microscopic features of Marasmius occultatiformis (LE 295973). A. Spores. B. Basidia. C. Cheilocystidia. D. Pileipellis cells.―Scale bar = 10 μm.

Habitat and distribution: Solitary or in small groups on needle-leaf litter in different types of mixed forest with Pinus koraiensis and various broadleaved trees. In the Russian Federation distributed from East Siberia (Jewish Autonomous Region) and Moneron Island (Sakhalin Region) to southern Sikhote-Alin and Manchurian mountain systems. Originally described from the Republic of Korea .

Specimens examined: RUSSIAN FEDERATION. Jewish Autonomous Region: Bastak State Nature Reserve, Mt. Chernukha, mixed forest, on litter, 7 Sept. 2001, E. Bulakh (VLA M-16.439!); ibid., upper reaches of Ikura river, mixed forest, on litter, 11 Aug. 2006, E. Bulakh (VLA M-21.215!). Sakhalin Region: Moneron Island, Picea -forest, on litter, 22 Jul. 2004, V. Barkalov (VLA M-19639!). Primorsky Territory: UNR, vicinity of Peishula field reserve station, valley of Malaya Suvorovka river, mixed forest ( Quercus mongolica , Pinus koraiensis , Acer spp. , Abies nephrolepis , etc.), on needle-leaf detritus litter, 14 Aug. 2011, A. Kiyashko (LE 295973!); ibid., mixed forest, on litter, 15 Aug. 2011, V. Malysheva (LE 295975!); ibid., southern slope of Mt. Zmeinaya, mixed forest ( Quercus mongolica , Pinus koraiensis , etc.), on needle-leaf litter, 43º38′26″ N, 132º33′19″ E, 17 Aug. 2011, A. Kiyashko (LE 295974!); ibid., near the peak of Mt. Zmeinaya, mixed forest ( Quercus mongolica , Pinus koraiensis , Abies nephrolepis , Acer spp. , Fraxinus sp. , etc.), on leaf litter, 17 Aug. 2011, A. Kovalenko and E. Malysheva (LE 289489! LE 289490!); KPNR, right watershed of Anan’yevka and Gryaznaya rivers, at the middle stream, mixed forest ( Pinus koraiensis , Abies spp. , Acer spp. , Carpinus cordata , Ulmus spp. , etc.), on needle litter, 43º23′09″ N, 131º32′14″ E, 01 Sept. 2011, A. Kiyashko (LE 289491!); ibid., mixed forest, on litter and twigs, 43º23′08″ N, 131º32′13″ E, 01 Sept. 2011, N. Psurtseva (LE 289492!); ibid., mixed forest, on litter, 31 Aug. 2011, E. Malysheva (LE 295976!); ibid., plateau, mixed forest, on litter, 01 Sept. 2011, E. Malysheva (LE 295977!); vicinity of Vladivostok, Ocean Ridge, mixed forest, on litter, 09 Sept. 2013, E. Malysheva (LE 295995!).

Observations: M. occultatiformis was described in 2012 based on a study of one specimen ( BRNM 718674 , holotype) collected in the Republic of Korea ( Antonín et al. 2012a). The examination of our additional collections contributes to the knowledge of the morphological features and geographical distribution of this species. M. occultatiformis appears to be a species having medium-sized basidiocarps (up to 20 mm in diam.), with a non-sulcate but slightly rugulose or pitted pileus centre, dry, more or less monotonously coloured from bright orange to reddish or brownish orange; lamellae with a concolorous or orange-brown coloured edge; and a cartilaginous stipe deep reddish brown at base. Our observations revealed an appreciable variability in basidiospore dimensions [6.5–10.8(11) × 3.1– 4.8 µm], with slightly higher average dimensions and Q than given in the holotype description. Also the dimensions of the main body of the cheilocystidia can vary up to 28.5 µm. Other additional features observed in the new material and not mentioned in the holotype are the presence of dimorphous cheilocystidia ( LE 289489) and caulocystidia in the upper part of the stipe in one specimen ( LE 295974). Some studied specimens have 2-spored basidia mixed with 4-spored ones .

In the course of the present work we generated 11 sequences of this species for the first time, which gave us a chance to study the relationships of M. occultatiformis with close taxa (Fig. 4). Based on morphological characters, the most similar species is Marasmius abundans Corner , but it differs from M. occultatiformis by having a paler coloured, greyish orange to golden yellow pileus and considerably larger basidiospores (12–18 × 4–5 µm) ( Antonín et al. 2012a). However in the ITS phylogenetic tree (Fig. 4), these species are located in different clades but without any reliable statistical support. The ITS pairwise distance between them is rather high (3.4–4.5%), which confirms the independence of these two taxa.

The northernmost collections were made in Bastak State Nature Reserve ( East Siberia , Jewish Autonomous Region ) at 48°56′ N, 133°07′ E situated in a rather severe monsoonal climate. All Russian specimens were predominantly collected in mixed forests with Pinus koraiensis and needle-leaf litter .

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.