Hohenbuehelia incrustata Ageev, Bulyonk., Zvyagina & Filippova, 2025

Ageev, Dmitriy, Bulyonkova, Tatiana, Zvyagina, Elena & Filippova, Nina, 2025, Hohenbuehelia incrustata sp. nov., a new species of Hohenbuehelia (Pleurotaceae, Agaricales) from Northwestern Siberia, Russia, Phytotaxa 683 (2), pp. 133-144 : 137-139

Hohenbuehelia incrustata Ageev, Bulyonk., Zvyagina & Filippova , sp. nov. Figs 1–3

MycoBank: MB851546

Diagnosis: —Fruitbodies sessile, small, ungulate- or fan-shaped, tomentose to pubescent, dark brownish gray and silvery frosted, lamellae with mouse-gray edges; pleurometuloids short almost immersed, fusiform, thick-walled, unusually heavily encrusted; pileipellis with abundant crystals; on dead branches of Sorbus aucuparia L. (1753: 477)

Holotype: — Russia, Northwestern Siberia, Khanty-Mansi Autonomous Okrug – Yugra region, vicinity of Shapsha village , N61.0559°, E69.4055°, 11.06.2015, Filippova N. V., YSU-F-05021!, GenBank—PP058161.

Paratype: — Russia, Northwestern Siberia, Khanty-Mansi Autonomous Okrug –Yugra region, vicinity of Shapsha village, N61.0653°, E69.4722°, 08.06.2015, Filippova N. V., YSU-F-04996!, GenBank—PP058160.

Etymology:— incrustata , encrusted, referring to the unusually heavily encrusted metuloids and abundant crystals embedded in the pileipellis.

Morphological characters:— Fruitbodies sessile, pleurotoid, ungulate with a slightly incurved margin when young, becoming fan-shaped with a deflected, somewhat wavy edge. Pileus 10–30 mm wide. Pileus surface dark brownish gray, densely tomentose to pubescent, covered with erect pyramidal tufts of colorless fibrils discernible under the lens, appearing as silvery gray frosting to the naked eye. Lamellae crowded, narrow, grayish-buff with darker gray edges concolour with pileus surface. Flesh thin, grayish-white, with a distinct semitranslucent layer under the upper surface. Odor and taste not recorded.

Microscopic characters:— Pileipellis a cutis, consisting of a thin suprapellis 15–30 µm thick made up of nearly hyaline thin-walled or slightly thick-walled, sinuous, cylindrical to irregularly inflated elements 3.3–7.2 (5.4) µm wide, arranged in with deep brown intracellular and encrusting pigment, with abundant crystals of yellowish to brownish resinous material embedded in the matrix, and a subpellis 40–65 µm thick, made up of branching filamentous hyphae 1.8–3.3 (2.8) µm wide, hyaline or with brown intracellular and encrusting pigment. Gelatinous layer under the pileipellis well-developed, approximately 150–300 µm thick, made up of hyaline, partially collapsed and gelatinized, branching and anastomosing filamentous hyphae 1.7–2.9 (2.7) µm wide. Pileus trama 150–400 µm thick, made up of relatively uniform more or less parallel thin-walled hyphae, filamentous or slightly constricted near the septa, with hyaline or slightly granular contents and occasionally somewhat uneven surface. Lamella trama made up of subparallel hyphae homologous to pileus trama hyphae. Subhymenium 25–30 µm thick, made up of compact, short, strongly racemose hyphae 3–6.4 (4.6) µm wide. Basidia 4-spored, narrowly clavate to almost cylindrical 21.6–27.6 (24.6) × 5.9–7.2 (6.6) µm, hyaline. Velum well-developed, covering the entire pileus surface, made up of hyaline solid or very thick-walled filamentous hyphae 3.3–7.1 (5.4) µm wide, appearing refractive, smooth or with small spherical protrusions more abundant towards the base, fused into bundles forming erect pyramidal scales up to 350 µm high. Basidiospores ellipsoid to slightly phaseoliform, smooth, hyaline, inamyloid, 7.0–9.1 × 3.6–4.5 µm (avg 8.0 ± 0.4 × 4.0 ± 0.2) Q = 1.8–2.3 (avg 2 ± 0.12), N =40. Pleurometuloids moderately numerous, fusiform, 43.9–67.2 × 8.6–14.7 µm (on average 55.5 × 11.6) (n=20), with brown intracellular pigment, with thick yellowish walls up to 3 µm; arising from occasionally refractive and pigmented hyphae of the trama; copiously encrusted with yellowish or brownish resinous material covering anywhere from the upper fifth to the whole surface, to the point of forming masses up to 6 µm thick. Cheilocystidia scarce, clavate to narrowly clavate, occasionally lecythiform, 18–32 × 6.2–7.1 µm, hyaline or with brownish intracellular pigment. Pileometuloids very scarce and possibly underdeveloped, observed in the examined material as several fractured fragments of thick-walled, heavily encrusted cells appearing similar to hymenial metuloids, but smaller and more irregular-shaped. Future collections of the species should be examined for the presence of pileometuloids. Clamp connections present in all tissues.

Material examined:— Russia, Northwestern Siberia, Khanty-Mansi Autonomous Okrug –Yugra region, vicinity of Shapsha village, YSU-F-04996!, 08.06.2015, Filippova N. V, on the stem of a dead rowan ( Sorbus aucuparia L.) in a predominantly aspen forest with scattered Betula and coniferous undergrowth after a clear cut, N61.0653°, E69.4722°;— Russia, Northwestern Siberia, Khanty-Mansi Autonomous Okrug –Yugra region, vicinity of Shapsha village, YSU-F-05021!, 11.06.2015, Filippova N. V. on branch of standing dead Sorbus aucuparia , in mixed predominantly aspen forest with well-developed coniferous undergrowth that had been clear cut several decades earlier, N61.0559°, E69.4055°.

Figures

FIGURE 1. Hohenbuehelia incrustata. a) overview of fresh fruitbodies on substrate; b) hymenium under lens showing dark lamellae edges; c) hymenium in dry state; d) pileus surface detail under lens.

FIGURE 2. Hohenbuehelia incrustata. a) cross-section of the pileus (top on the left), bar = 100 µm; b) pileipellis and velum details; c) metuloids; d) spores.

FIGURE 3. Hohenbuehelia incrustata. a) metuloids; b) metuloid covered with copious crystals, originating from the trama, and subhymenium; c) spores; d) cheilocystidia; e) basidia. Bar = 50 µm (a, b, d, e), 10 µm (c).