Hemimycena longipleurocystidiata Niveiro, Popoff & Albertó, 2014

Niveiro, Nicolás, Popoff, Orlando F. & Albertó, Edgardo O., 2014, Hemimycena longipleurocystidiata (Mycenaceae, Agaricomycetes), a new species from the Argentinean Atlantic Forest, Phytotaxa 177 (1), pp. 49-55 : 50-53

Hemimycena longipleurocystidiata Niveiro, Popoff & Albertó , sp. nov. ( Figs. 1–2 )

Mycobank MB 808684

Diagnosis:— Characterized by a thin and delicate pileus, 6–30 mm broad, a white pileus with a cream centre, and a translucent intervenose-striate surface, oblong to cylindrical spores, 8.1–12(–14.3) × 3.4–4(–5.3) µm in size; lageniform to fusiform pleurocystidia, 53–91 × 11–20 µm in size, and lageniform to nettle hair-shaped cheilocystidia, 59–83 × 11–15 µm in size.

Holotype:— ARGENTINA, Misiones : San Pedro , Moconá Provincial Park, Chachi trail (27°08’51.1’’S 53°53’50.0’’W, 341 m elev.), 26 May 2009, N. Niveiro & O. Popoff 1393 ( CTES 0590529 ).

Pileus 6–30 mm broad, convex to applanate, with depressed centre, thin and delicate, surface white (1A1) to offwhite (between 1A1 and 1B1), centre cream (4A2) to light brown (5A2), dry, glabrous, hygrophanous, translucent intervenose-striate towards the centre when moist. Margin straight to wavy. Pileal context fleshy, thin, white; odour and taste not tested. Lamellae well-developed, intervenose, white (1A1) to cream colour (4A2), distant to subdistant, adnexed, rather ventricose, up to 4 mm broad, with even concolorous edge, with numerous lamellulae and veins that do not exceed half of the lamellae. Stipe central, 5–30 × 1–3 mm, cylindrical with bulbose base, up to 5 mm in diameter, white (1A1), densely pruinose, dry, without basal tomentum. Spore print white (1A1).

Basidiospores 8.1–12 (– 14.3) × 3.4–4 (– 5.3) µm, x = 11.78 × 4.39 µm, Q = 2.31–3.61, Q x = 2.69, n= 40; oblong to cylindrical, some slightly curved, hyaline, smooth, inamyloid, thin-walled, containing a single oil guttule. Basidia 23.6–28.5 (32) × 4.5–6 µm, clavate, 2- and 4-spored, hyaline, thin-walled, generally embedded in a gelatinous matrix that makes observation difficult. Pleurocystidia 53–91 × 11–20 µm, lageniform to fusiform, usually long pedicellate, thin- to slightly thick-walled in basal part, submerged in the hymenophoral trama and projecting from the hymenium up to 30–65 µm, abundant. Cheilocystidia 59–83 × 11–15 µm, lageniform to nettle hair-shaped (thickened towards the base with a long apical projection), sometimes subcapitate and with embedded olive pigments, abundant.Hymenophoral trama almost regular, hyphal walls gelatinized. Subhymenium strongly gelatinized. Pileipellis an ixocutis formed of prostrate hyphae, 3–6 µm diam., smooth, with walls slightly gelatinized. Stipitipellis a cutis composed of smooth hyphae of 3–6 µm diam., without gelatinized hyphae or caulocystidia. Clamp connections present.

Distribution and ecology: — Solitary and scattered on decaying wood inside the Atlantic rainforest of northeast Argentina, in the Province of Misiones.

Additional specimens examined:— ARGENTINA, Misiones : San Pedro , Moconá Provincial Park , Chachi trail (27°08’51.1’’S, 53°53’50.0’’W, 341 m elev.), 26 May 2009, N. Niveiro & O. Popoff 1394 Isotype ( CTES!). Ib. San Ignacio, Teyú Cuaré Provincial Park (27°08’51.1’’S, 53°53’50.0’’W, 110 m elev.), 23 May 2009, N. Niveiro & O. Popoff 1222 ( CTES!) .

Remarks: — Hemimycena longipleurocystidiata is characterized by its large pleurocystidia and cheilocystidia, a relatively large, completely white to cream colour basidiomata with an intervenose lamellate hymenophore. According to Antonín & Noordeloos (2004), due to its decurrent lamellae, inamyloid spores and a non dextrinoid trama, this species belongs in section Omphaliariae ( Antonín & Noordelos 2004) (= Mycena sect. Hiemales subsect. Omphaliariae ; Smith 1947, Maas Geesteranus 1991, Maas Geesteranus & de Meijer 1997).

In Argentina, prior to the discovery of the new species, only five species of this genus were known. Hemimycena patagonica Singer and H. nothofagi Singer grow in the Andean Patagonian region, but both species are smaller and do not exhibit the characteristic cystidia of H. longipleurocystidiata ( Singer 1969: 105, Raithelhuber 2004: 133). The other three species have been described in the centre and north of the country; H. cretacea Raithelh. , described from Buenos Aires Province, differs in having smaller spores: 4–5 × 3.7–5 µm and clavate to broadly clavate cystidia ( Raithelhuber 2004: 524). Hemimycena truncicola Singer , described from the Yungas forest, differs in its smaller basidiomata that do not exceed 5 mm in diameter, lack of pleurocystidia, and its cylindrical filamentous cheilocystidia ( Singer 1962b: 62). Hemimycena subtropicalis Singer , which also has smaller basidiomata, up to 2 mm diam, in addition to having markedly distant, reduced lamellae, lacks pleuro and cheilocystidia ( Singer 1959: 381).

Maas Gesteranus & De Meijer (1997) described two species of Mycena sect. Hiemales subsect. Omphaliariae from the same biogeographic region where H. longipleurocystidiata was found, named Mycena lepida Maas G. & de Meijer and M. straminella Maas G. & de Meijer. Both species differ from H. longipleurocystidiata . The former is distinguished by its small basidiomata (<5 mm diam.), the lack of pleurocystidia and the presence of subclavate to subcylindrical cheilocystidia, with a few coarse excrescences or somewhat lobed-furcated at the apex, rarely smooth. Mycena straminella , also a small species with pilei no more than 5 mm diam, has yellowish hues on the pileus surface and at the base of stipe, lacks pleurocystidia and has smooth cheilocystidia that are smaller than those of H. longipleurocystidiata .

Singer (1989) describes three species of Hemimycena from the Brazilian Amazonas, similar to the species described here: H. amazonica Singer , H. diplocystis Singer and H. pleurotiformis Singer. Hemimycena amazonica has a very small pileus, up to 2.5 mm diam., lacks pleurocystidia and has smaller, claviform cheilocystidia with a diverticulate apex ( Singer 1989: 67). Hemimycena diplocystis does not exceed 15 mm diam., is entirely white, lacks pleurocystidia, has ventricose cheilocystidia 26–37 × 6.5–11 µm and diverticulate pileipellis hyphae ( Singer 1989: 68). Hemimycena pleurotiformis (sensu Singer 1989: 69) presents a white pileus with a slight yellowish centre and pleurocystidia, but differs in that the pileus does not exceed 15 mm diam. It has smaller spores (6.3–7 × 3.3–4.4 µm) and smaller fusiform pleurocystidia (about 25 × 8 µm). Hemimycena pleurotiformis and H. longicystis R. Heim are probably the species most similar to H. longipleurocystidiata . Hemimycena longicystis , known from Venezuela and Bolivia in South America ( Dennis 1951: 454, Singer 1962b: 61) and Tanzania in Africa ( Pegler 1977: 216), is macroscopically very similar to the species described here. It has large, white basidiomata, up to 30 mm diam., with distant lamellae, but differs from H. longipleurocystidiata in its larger spores (11–16 × 3.5–5.2 µm) and the absence of pleurocystidia ( Pegler 1977: 216; Singer 1962b: 61).

We analysed the type material of Hemimycena longicystis [Singer B 707 ( LIL)]. It consists of a single pileus in a good state of preservation. Based on this collection, we observed: few spores (14–16 x 4–4.5 µm, n = 6), lageniform, long pedicellate cheilocystidia (54–65 x 10–15 µm), and no pleurocystidia. This is in agreement with the description made by Singer (1962: 61) .

Dennis (1961) described several species of Hemimycena for Venezuela, but none of them match the characteristics of this new species, and besides, all were subsequently transferred to other genera: Hydropus gigasporus (Dennis) Pegler , Hydropus sphaerosporus (Dennis) Dennis , Marasmiellus anomalus (Dennis) Dennis , Marasmiellus junquitoensis (Dennis) Dennis , Marasmiellus primulina (Dennis) Dennis , Marasmiellus roseipallens (Dennis) Singer , Mycena filicina (Dennis) Dennis , and Myena xanthopoda (Dennis) Dennis.

There are several similar species worldwide: Hemimycena pseudolactea (Kühner) Singer is very similar to H. longipleurocystidiata . Its pileus may occasionally reach 25 mm diam, and it has broadly fusiform pleurocystidia, but it differs in its smaller spores (6.9–7.8 x 2.6–4.4 µm) and pleurocystidia (25–60 x 8–15 µm) ( Malysheva & Morozova 2009: 61; Moser 1978: 171). Hemimycena lactea (Pers.) Singer could be mistaken for H. longipleurocystidiata in having a similar spore size, but it has distinctly smaller pleuro- and cheilocystidia (19–30 x 5.5–6 µm) ( Malysheva & Morozova 2009: 50). Other similar species are Hemimycena cucullata (Pers.) Singer ( Malysheva & Morozova 2009: 36, Moser 1978: 171) and Phloeomana speirea (Fr.) Redhead [= Hemimyena speirea (Fr.) Singer ] ( Maas Geesteranus 1991: 95, Smith 1947: 359) but both differ in having smaller basidiomata, no pleurocystidia and a pileipellis consisting of diverticulate hyphae.

Figures

FIGURE 1. Hemimycena longipleurocystidiata: A—Paratype [Niveiro & Popoff 1222 (CTES)], B—Holotype [Niveiro & Popoff 1393 (CTES)]. Bar: 10 µm.

FIGURE 2. Hemimycena longipleurocystidiata [Niveiro & Popoff 1393 (CTES)]: A—spores, B—pleurocystidia, C—cheilocystidia. Bar: 10 µm.