Crepidotus heterocystidiosus T. Bau & Y.P. Ge
MycoBank number: MB830017
Pileus (2.5–)8.0–24.0mm, when young translucent to white, ungulate, convex, with the white short fibrils, margin striae indistinct, not hygrophanous; at maturity white to whitish, flabelliform to semicircular, slightly concave, viscid, tomentose, margin distinctly striate, hygrophanous occasionally, with white villosity at the point of attachment. Stipe 1.0–3.0 × 0.5–1.0mm, obvious in young stages, cylindrical, at maturity short cylindrical to subglobose. Lamellae (1.5–)6.0–13.0mm broad, L=12–17, l=3–7, ventricose, white when young, later pinkish, at maturity brown, decurrent. Context white, thin. Odour and taste distinct. Spore print light brown. Basidiospores (5.7–)6.2–7.6(–8.1) × 4.3–5.2(–5.6) μm, Q=1.20–1.46(–1.54) [x =6.9 ×5.0μm, Qm=1.40], broad ellipsoid to ellipsoid, ovoid, in side view inequilateral, light brown to tea brown, smooth (under oil and SEM), oil inside occasionally. Basidia (14.4–)18.3–26.0 × (4.5–)5.2–6.5μm, thin-walled, mostly 4-spored, rarely 2-spored, clavate, side inflated sometimes, clamp connections absent. Pleurocystidia absent. Cheilocystidia (26.9–)41.8– 54.6(–64.2) × (2.8–)5.9–9.2μm, lageniform, often septate at apex, some with long flexuous upper portion, subcylindrical at base occasionally, clamp connections absent. Pileipellis a trichoderm, composed of long cylindrical hyphae, (44.6–)64.4–73.8 × 2.4–2.9μm, underneath by cylindrical hyphae at base, 28.2–26.5(–46.8) × 4.5–6.9μm, gelatinous layer 50–70μm, clamp connections usually absent, but present occasionally.
Habitat: Gregarious, on the bark cracks of Eucalyptus.
Additional material examined: CHINA. Yunnan Province: Kunming City, Kunming Botanical
Garden, 6 Aug 2016, Ge & Yan HMJAU37034, HMJAU37038; Black Dragon Pool Park, 1 910m a.s.l., 25°13.11′N, 102°74.43′E, 6 Aug 2016, Ge & Yan HMJAU37053 (HMJAU). Wenshan County,
Longpingba, 29 Jul 1959, Wang & Teng HMAS26994; Dali City, Yangbi, 20 Aug 1959, Wang & Teng HMAS 26995; Jingdong County, Ailaoshan Nature Reserve, 15 Jul 2014, Wei HMAS271741. Hunan Province: Chenzhou City, Chenzhou Park, 9 Sep 1981, Mao HMAS42258. Guangxi Zhuang Autonomous Region: Naning City, Daming Mountain, 17 Dec 1997, HMAS32291. Tibet: Milin, Mao HMAS52680 (HMAS); Changdu Country, 3 350m a.s.l., 27 Jul 2004, Ge HKAS45967 (HKAS).
Note: Clamp connections have been regarded as a stable character to distinguish subg. Crepidotus from other subgenera, but the reliability of this character at the genus level is controversial. Senn-Irlet (1995) suggested that clamp connections exist in the different subgenera but gelatinised hyphae were found in subg. Crepidotus. Members of subg. Crepidotus, Crepidotus mollis, C. calolepis var. calolepis and C. calolepis var. squamulosus (Cout.) Senn-Irlet, reported from Europe (Senn-Irlet 1995), share the same characters as C. heterocystidiosus in having smooth spores, but the larger spores, narrow lageniform to clavate cheilocystidia and dissimilar pileipellis distinguish these taxa from C. heterocystidiosus. Amongst the specimens from North America, examined by Hesler & Smith (1965), 26 species and three varieties were recorded in subg. Crepidotus. Amongst these taxa, C. alabamensis Murrill, C. coloradensis Hesler & A.H. Sm. and C. uber (Berk. & M.A. Curtis) Sacc. produce spores of the same shape and size as those of C. heterocystidiosus. The lageniform to clavate cheilocystidia without branches at the apex and interwoven pileipellis with forked or numerous branched pileocystidia are useful characters for distinguishing C. alabamensis from C. heterocystidiosus. Crepidotus coloradensis has a buff, greyish-yellow or pink-tinged pileus that different from C. heterocystidiosus. Crepidotus uber is separable from C. heterocystidiosus, based on clavate cheilocystidia, slight larger spores and non-sticky pileipellis. In addition, the stipe of C. heterocystidiosus is visible at all stages of development and this character enables easy differentiation from closely related species.
Fig. 1 RAxML tree and phylogenetic relationships of Crepidotus. Inocybe species were served as outgroup. Maximum likelihood support values (>50%) and posterior probabilities (>0.80) are showed on main branches (ML/PP).
Fig. 2 Fig 2. Microscopic features of Crepidotus heterocystidiosus (HMJAU 37053). a: Basidiomata; b: Basidiospores; c: Basidia; d: Pileipellis; e: Cheilocystidia. Bars: a=10mm; b=5μm; c–e=10μm.