Entoloma (Fries, 1838) P. Kummer, 1871

Morozova, Olga, Popov, Eugene, Alexandrova, Alina, Pham, Thi Ha Giang & Noordeloos, Machiel Evert, 2022, Four new species of Entoloma (Entolomataceae, Agaricomycetes) subgenera Cyanula and Claudopus from Vietnam and their phylogenetic position, Phytotaxa 549 (1), pp. 1-21 : 13-15

Entoloma iсarus O.V. Morozova, E.S. Popov & Noordeloos, sp. nov. (Figs. 7, 8)

Mycobank: MB 843252

Type:— VIETNAM. Gia Lai Province, K’Bang District, Son Lang Commune , Kon Chu Rang Nature Reserve , near the camp, N 14.505520°, E 108.541610°, 1050 m a.s.l., on decaying wood in middle-mountain evergreen mixed forest with a predominance of Podocarpaceae ( Dacrydium elatum , Dacrycarpus imbricatus ), Magnoliaceae , Burseraceae (Canarium) , Myrtaceae (Syzygium) , 26 May 2016, E. Popov (holotype: LE F-312696 (!), isotype in VRTC (!), ITS sequence GenBank OM987257 , LSU sequence GenBank OM996174 ).

Etymology:—Ἴκαρος (Greek), Îcărus (Lat.) in Greek mythology, was the son of the master Daedalus, the creator of the Labyrinth. Icarus and Daedalus attempted to escape from Crete by means of wings that Daedalus had constructed from feathers and wax. Icarus ignored his father’s instructions not to fly too close to the sun, and the wax in his wings melted. He fell out of the sky into the sea and drowned. The butterfly Polyommatus icarus was named after him. The new Entoloma species is named after this butterfly, due to the similarity of color.

Diagnosis:— Entoloma icarus is characterized by the eccentrically stipitate to pleurotoid basidiomata with a minutely squamulose blue pileus and whitish or blue-tinged short stipe, the initially uniformly colored pileus, which becomes distinctly translucently striate with small blue squamules on a paler greyish beige background with age. Microscopically, the rather large spores and sterile lamellar edge composed of cylindrical to narrowly clavate cystidia are characteristic.

Description: Basidiomata small to medium-sized, pleurotoid or with eccentric stipe. Pileus 10‒25 mm diam., hemisphaerical to convex soon expanding to plano-convex with flat to slightly depressed centre, eccentric, with deflexed then straight margin, hygrophanous, translucently striate to half the radius, becoming sulcate with age, firstly radially fibrillose, greyish blue to dull or deep blue (21D–F5‒7), then covered with dark blue squamules on a bluish or brownish grey background (20C–D2‒3, 6C–D2‒3), more dense at first becoming sparse, discoloring to brownish grey with bluish pileus margin. Lamellae moderately distant, adnate-emarginate, ventricose, whitish with or without bluish tinge, becoming pinkish, with entire blue edge. Stipe 5–10 × 1–1.5 mm, lateral, cylindrical, slightly innately fibrillose, pubescent, whitish or bluish, with white tomentum at base. Context greyish. Smell indistinct, taste not reported.

Basidiospores (10–)11.8–12(–13.3) × (7.2–)8(–9) μm, Q = (1.4–)1.5(–1.6), heterodiametrical, with 5–7 rather sharp angles in side-view. Basidia 24–30 × 9–10.5 μm, 2–4-spored, narrowly clavate, clampless. Cheilocystidia 33–53 × 7.5–14 μm, cylindrical to narrowly clavate, sometimes septate, non pigmented, forming a sterile lamellar edge. Pileipellis a cutis of cylindrical hyphae 2–7 μm diam with ascending cylindrical to narrowly clavate terminal elements (45–90 × 10–17 μm), that macroscopically form the squamules. Clamp connections absent.

Habitat and distribution:—In small groups on wood in the middle-mountain evergreen mixed forests. Known only from Vietnam.

Additional specimens examined:— VIETNAM. Gia Lai Province, K’Bang District, Son Lang Commune, Kon Chu Rang Nature Reserve, near the camp, N 14.505520°, E 108.541610°, 1050 m a.s.l., on decaying wood in middle-mountain evergreen mixed forest with a predominance of Podocarpaceae ( Dacrydium elatum , Dacrycarpus imbricatus ), Magnoliaceae , Burseraceae (Canarium) , Myrtaceae (Syzygium) , 26 May 2016, E. Popov (LE F-312697 (!), ITS sequence GenBank OM987258 ).

Notes:— Entoloma nubilum Manim., Leelav. & Noordel. described from India differs by the non hygrophanous, non translucent-striate pileus, smaller spores and absence of cheilocystidia ( Manimohan et al. 2002). Entoloma cyanomelaenum known only from the type locality in Sumatra possesses smaller spores (9–11 × 5.5–6.5 μm), lacks cystidia and the pileus turns red in KOH ( Boedijn 1929; Horak 1980). Entoloma gainsvillae Morgan-Jones (1971: 1052) (= E. cyaneum ( Murrill 1943: 429) Hesler (1967: 13) [non E. cyaneum (Peck 1873: 49) Saccardo (1887: 688) ]) from Florida differs by smaller spores (8–10 × 6–7 μm) and lack of cheilocystidia ( Murrill 1943; Hesler 1967; Morgan-Jones 1971).