Dennisiomyces fibrillosus Corriol & Jargeat, 2019

Corriol, Gilles & Jargeat, Patricia, 2019, Morphological and phylogenetical description of Dennisiomyces fibrillosus sp. nov. (Agaricales, Tricholomataceae) from the Pyrenees and the first record of the genus in Europe, Phytotaxa 405 (5), pp. 226-236 : 230-233

Dennisiomyces fibrillosus Corriol & Jargeat sp. nov. ( Figs. 2 , 3 , 4 )

Mycobank:—MB830036

Etymology:—‘fibrillosus’ refers to the fibrillose veil that covers the pileus of young specimens.

Diagnosis:— Sporocarpia a mycenoideis ad inocyboidea, epicute fibrilloso opaco, sporis hyalinis, amyloideis, breviter ellipsoideis; acie lamellarum sterilibus cylindrico-clavatisque pilis tecta; trama lamellarum parallela, cum mediostrato distincto, hyphis fibulatis, pigmento mixto intracellulari parietalique paululum incrustanti; saprotrophus humicolus, in silva frondosa temperatarum regionum, in solo cum opulentis nutrimentis.

Holotype:— FRANCE. Hautes-Pyrénées , Arcizans-Avant , Ravine of the Gave d’Azun, right bank, alt. 480 m, 6 October 2017, G. Corriol GC 17100604 in BBF

GenBank:—ITS MK569404, LSU (28S) MK569398, SSU (18S) MK569400, RPB2 MK577919

Description:— Pileus 5–22 mm, conical and convex in its lower part, margin undulate, extending over edge of pileus, slightly irregular, with long fibrils and a matt coating of white fibrils on a yellowish gray-brown background at the disc (2.5 Y 5/4) and yellowish creamy white on the margin (2.5 Y 7/4–7/6), slightly hygrophanous. Lamellae ventricose and deeply emarginate at the insertion point, distant (18–28 lamellae per basidiome), with frequently 1–2 tiers of lamellulae, rather thick, some forked or anastomosed, a very pale yellowish color in youth (2.5 Y 8/2), and then more yellow (2.5 Y 8/3), with a slightly irregular or eroded edge of the same color. Stipe 15–35 × 1–4 mm, cylindrical or quite often flexuose, with a white powdery coating on the upper part, fibrillo-striate with white below, on a creamy white background (2.5 Y 8/2). Veil rudimentary, transitory, white, forming a cortina that links the margin to the stipe in primordia and leaves a pattern of silky remnants on stipe. Basal mycelium white, agglomerating plant debris and superficial organic matter turned into humus, probably saprotrophic. Flesh whitish, Odour weakly spermatic, taste like hazelnut. Exsiccatae brown at the disc level (7.5YR 3/4), remaining paler, brown-yellow, near the margin (7.5YR 4/6–10YR 5/8).

Basidiospores D1, 9 [N=37] (6.0)6.3– 6.8 –8.0(9.2) × (4.6)4.9– 5.4 –6.1(6.5) μm; Q = (1.12)1.16– 1.30 –1.42(1.44); shortly ellipsoid, with a wide and short apiculus, smooth, hyaline, thin-walled, amyloid (blue-gray), with a noncyanophilous wall, but the endospore stains dark blue in Cotton Blue on a few altered spores, enhancing a reticulate structure, containing a large oleiferous metachromatic drop in Cresyl Blue. Basidia mainly tetrasporic, with a few bisporic ones, measuring 36–46 × 6–10.5 μm, cylindro-clavate, a few of them with an entirely thickened wall, densely filled with small refringent granules, non-siderophilous in iron-acetocarmine red at a high temperature, forming metachromatic drops in Cresyl Blue. Successive treatments in KOH and Congo Red cause rhomboidal crystals to precipitate inside the basidia. Sub-hymenium composed of branched hyphae some containing metachromatic oleiferous drops in Cresyl Blue. Lamellar margin covered with sterile clavate cells (more rarely with an appendix), thin-walled, looking empty or nearly empty, with a terminal element measuring 20–45 × 6–10(13) μm. Pleurocystidia hard to identify, some supposedly sterile structures could be mistaken for monosporic basidia, while others, more clearly fusiform or with a slightly sinuous appendix could be considered as cystidia; they frequently contain large metachromatic oleiferous drops in Cresyl Blue and measure 24–45 × 6.5–9 μm. These hymenial cells are scarce. Lamellar trama parallel, made up of a mid-layer of broad hyphae, more or less elongate, often rather short (20–50(200) × 8–25 μm), between two layers of narrow hyphae (× 3–8 μm), with quite a number of scattered, sinuous, 5–10 μm wide laticifers. Pileipellis made of up of erect hyphae, with numerous cylindro-clavate or often tortuous terminal elements, with a brown intracellular diffuse pigment and an inconspicuous cell wall pigment, very finely pitted in places, no gelatinization. Pileus trama made up of parallel hyphae, with rather close septae (cells measuring 5–100 × 8.5–18.5 μm) becoming shorter with depth. Stipitipellis made up of thin parallel hyphae, with dense tufts of clavate, more or less septate hairs in the upper third, more rarely lageniform with a wide neck or wide excrescences. Clamp connections abundant in all tissues.

Other material examined:— FRANCE. Hautes-Pyrénées, Arcizans-Avant, Ravine of the Gave d’Azun, right bank, alt. 480 m, 9 November 2018, G. Corriol GC 18110903 in BBF.

Habitat:—both collections were found in the same place, in the thick and well-aerated litter of a stand of various deciduous trees (e.g. Fraxinus, Tilia, Ulmus, Corylus ), on the higher alluvial terrace of a river with nival torrential regime, in an alkaline and nutrient-rich soil, in a confined humid atmosphere, with high biological activity (mull humus), along with Pseudobaeospora dichroa f. cystidiata Bas (2002: 120) , P. pyrifera Bas & L.G. Krieglst. (1998: 204) , P. calcarea Clémençon & Ayer (2007: 281) , Pseudobaeopsora cf. basii Adamčik & Ripková (2004: 2) , Entoloma nausiosme Noordel. (1987: 96) , E. versatile (Gillet) M.M. Moser (1978: 2009) , Ramariopsis rufipes (G.F. Atk.) R.H. Petersen (1964: 274) , Clavaria flavostellifera Olariaga, Salcedo, P.P. Daniëls & Kautman (2015: 107) .

Figures

FIGURE 2. Dennisiomyces fibrillosus, holotype;A. spores, B. basidia and basidiola, C. edge sterile hairs, D. caulocutis; E. epicutis. Scale bars: 10 μm; drawings by Gilles Corriol.

FIGURE 3. A. crystals in the basidia after treatment with KOH 5% and staining with Congo Red; B. reticulate aspect of damaged spores in lactic cotton blue; C. basidia with a thickened cell wall and a metachromatic content in Cresyl Blue; D. pleurocystidoid structure with a metachromatic content in Cresyl Blue; E. two pleurocystidoid structures in distilled water; F. part of a gill edge covered with sterile hairs, in Congo Red; G. pileus trama in distilled water; H. lamellar trama in Congo Red; I. sub-hymenium in Congo Red. Microscope photographs by Gilles Corriol.

FIGURE 4. Dennisiomyces fibrillosus, A. holotype, basidiomes in situ, Arcizans-Avant, Hautes-Pyrénées; B. collection of 9th November 2018, basidiomes in situ, same locality. Photographs by Gilles Corriol.