Parasola tenuissima T. Bau & L. Y. Zhu, 2025

Zhu, LiYang & Bau, Tolgor, 2025, Emendation of morphology and infrageneric standards of Parasola (Psathyrellaceae, Agaricales) and its species diversity in China, IMA Fungus 16, pp. e 143796-e 143796 : e143796-

Parasola tenuissima T. Bau & L. Y. Zhu sp. nov.

Figs 12 a – c , 13

Diagnosis.

Basidiomata tiny-sized. Pileus less than 10 mm in diameter, orange-brown in center, often with a conspicuous depressed disc; stipe white to pale gray at upper part, brown to sandy beige at lower part, sometimes translucent; basidiospores 9.7–10.1 × 7.9–8.2 × 6.1–6.6 μm, most in ovoid, ellipsoid or limoniform in front view, flattened, ellipsoid to narrow ellipsoid in side view, dark olive-brown to almost black; basidia dimorphic, 4 - spored; lamella trama dark olive-brown; cheilocystidia 18–49 × 11–24 μm, utriform, ellipsoid or fusiform; pleurocystidia 38–77 × 16–26 μm, sublageniform or (sub) cylindrical; pileipellis a hymeniderm at yellow-brown sulcate, mainly made up of ellipsoid or clavate cells, sometimes subglobose or utriform with short pedicels; sclerocystidia absent.

Etymology.

The epithet “ tenuissima ” refers to the slender basidiocarps of this species.

Type.

CHINA • Jilin Province, Changchun City, Nanhu Park , 43°85'25"N, 125°29'98"E, 218 m a. s. l., on humus layer of broad-leaved tree, August 17 th 2022, S. E. Wang and L. Y. Zhu, HMJAU 64084 (E 2208213, holotype) .

Description.

Basidiomata tiny-sized. Pileus 4–6 × 7–10 mm when still closed, 8–10 mm when mature, at first ovoid or ellipsoid, finally almost flattened, often with a conspicuous depressed disc at center; dry; cream to light yellow-brown at margin and orange-brown in center when young, pale gray but always with brown hue at age, sometimes with water-soaking texture; sulcate-striate almost up to center. Context extremely thin, pale brown or almost unseen, odor and taste not distinctive. Lamellae medium crowded, free and remote from stipe by pseudocollarium, 1 mm in wide, L = 27–32, I = 0 or 1, first white to beige, pale gray when expanded; hardly deliquescent with age. Stipe 35–51 × 1–2 mm, cylindrical, hollow, equal or attenuate towards the apex, slender, white to pale gray at upper part, brown to sandy beige at lower part, sometimes translucent, glabrous. Spore print not recorded.

Basidiospores [50, 4, 3] (8.9 –) 9.7–10.1 (– 12.2) × (7.4 –) 7.9–8.2 (– 9.2) × (5.9 –) 6.1–6.6 (– 6.7) μm, Q 1 = 1.10–1.47, Q 2 = 1.41–1.75, av. Q 1 = 1.25, av. Q 2 = 1.53; most in ovoid, ellipsoid or limoniform in front view, with apical papilla and convex base, flattened, ellipsoid to oblong in side view; smooth, dark olive-brown, dark red-brown to almost black, with yellow-brown oil droplet; inamyloid; germ pore eccentric, 1.5–2.5 μm wide. Basidia dimorphic, 17–36 × 8–13 μm, sterigma 4–7 μm, clavate, occasionally constricted in middle part, hyaline, 4 - spored, surrounded with 4–6 pseudoparaphyses; obvious subhymenium unseen. Cheilocystidia abundant, 18–49 × 11–24 μm, utriform, ellipsoid or fusiform, smooth, colorless, thin-walled. Pleurocystidia 38–77 × 16–26 μm, sublageniform or (sub) cylindrical, colorless, thin-walled. Lamellar trama regular, 4–7 μm wide, hyaline, dark olive-brown, thin-walled. Pileipellis a hymeniderm at yellow-brown sulcate, mainly made up of clavate cells, sometimes subglobose or utriform with short pedicels, 16–42 × 11–23 μm, hyaline, with brown hue at base; other part of pileus with gray hue a cutis, made up of hyaline, colorless to light brown, 2–3 μm; pileus trama hyphae slightly interwoven, thin-walled, hyaline, yellow-brown to yellow, 4–7 μm wide. Sclerocystidia absent. Caulopellis hyphae parallel, 2–7 μm wide, hyaline, thin-walled, often short-diverticulate; hyphae of stipe trama 10–16 μm wide, colorless, thin-walled; caulocystidia unseen. Clamp connection and pseudoclamp present.

Ecology.

Solitary, subfasciculate, or in small groups grow on humus layer in broad-leaved forest with Quercus mongolica , Malus baccata , Acer and Ulmus or under bush of Chimonanthus nitens . Fruiting in August to September. Only known from northeast China.

Other specimens examined.

CHINA • Jilin Province, Jilin City, Jiaohe City, Qianjin Forest Farm , 43°54'35.8"N, 127°39'11.8"E, 343 m a. s. l., July 23 rd 2022, L. Y. Zhu, H. B. Song and X. Wang, HMJAU 60098 (Z 22072316) ; CHINA • Jilin Province, Yanbian Korean Autonomous Prefecture, Antu County, Erdaobaihe Town, Chinese Mermanser Park , 42°41'73.7"N, 128°11'40.5"E, 719 m a. s. l., August 1 st 2022, L. Y. Zhu, HMJAU 64085 (Z 22080101) ; CHINA • Jilin Province, Changchun City, Jingyuetan National Forest Park , 43°79'72.1"N, 125°46'52.3"E, 308 m a. s. l., August 18 th 2022, L. Y. Zhu, HMJAU 64086 (Z 22081803) .

Notes.

Phylogenetically, Parasola tenuissima and Parasola chowii are closely related. Distinguishing itself from the former, Parasola chowii exhibits slightly larger basidiocarps, with expanded pileus reaching up to 1.4 cm in diameter. Moreover, the lamellae are densely arranged with L = 35–41, and the basidiospores appear subglobose to broadly ellipsoid or ovoid in front view.

Known species with brown stipes in Parasola until now are only Parasola plicatilis-similis L. Nagy, Szarkándi & Dima , Parasola parvula Ganga & Manimohan and Parasola tenuissima , however, Parasola plicatilis-similis has relatively larger basidiocarps whose pileus are up to 15–45 mm when expanded ( Szarkándi et al. 2017). Differed from Parasola tenuissima , Parasola parvula has pileus with purple hue and sparser lamellae (L = 19–20) ( Ganga and Manimohan 2018).

Figures

Figure 12. Basidiomata of species in Clade Plicatilis and Clade Misera of sect. Parasola. a – c Parasola tenuissima: a HMJAU 64085, b HMJAU 64086, c HMJAU 64084; d – f Parasola chowii: d HMJAU 60358, e HMJAU 60374, f HMJAU 64099; g – l Parasola neoplicatilis: g, h HMJAU 64087, i HMJAU 64088, j, k HMJAU 60084, l HMJAU 64089; m, n Parasola plicatilis: m HMJAU 60367, n HMJAU 60366; o Parasola megasperma HMJAU 60099.

Figure 13. Basidiomata and microscopic structures of Parasola tenuissima (HMJAU 60098, HMJAU 64084, HMJAU 64085, HMJAU 64086): a basidiomata, b pileipellis, c basidiospores, d basidia, e cheilocystidia, f pleurocystidia, g stipitipellis. Scale bars: 1 cm (a); 10 μm (b – g).