Hymenopellis aff. orientalis (R.H. Petersen & Nagas.) R.H. Petersen

Niego, Allen Grace T., Thongklang, Naritsada, Hyde, Kevin D. & Raspe, Olivier, 2023, Introduction of two novel species of Hymenopellis (Agaricales, Physalacriaceae) from Thailand, MycoKeys 98, pp. 253-271 : 253

Hymenopellis aff. orientalis (R.H. Petersen & Nagas.) R.H. Petersen

Figs 6 , 7

Description.

Basidiomata small-sized. Pileus 15 mm diam., convex with an umbo, light brown (4B4) with slightly darker color at the center brown (5C5), paler toward margin, non-hygrophanous, slightly viscid, appressed-squamulose surface, radially wrinkled; margin inflexed, translucently striate; context white to cream (1A3), unchanging when cut, consistency rubbery. Lamellae subventricose, rubbery to rather soft, 3 mm broad, 0.5 mm thick, adnate with slight decurrent tooth, white, subdistant (1 mm apart); lamellar margin finely fimbriate; lamellulae present, in 1-2 tiers. Stipe 67 mm × 2.5 mm, central, cylindrical, tapered upwards, slightly clavate base, whitish to light brown (4A2) from the pileus to slightly darker (4B4) downwards, stuffed to fistulose; surface dry, fibrillose, finely dotted to minutely appressed-squamulose especially towards the base, which is covered with white tomentum; context white, unchanging when cut; pseudorrhiza present, 60 mm long. Annulus and volva absent. Spore print white. Smell indistinct. Taste mild.

Basidiospores [50,1,1] (13.5) 15-16.4-17.5 (18) × (9.5)-13-13.5 (14.5) μm (Q = 1.2-1.4, Q* = 1.3), broadly ellipsoid to ellipsoid, ovoid, obovoid, thin-walled, delicately puckered, hyaline in 5% KOH. Basidia [30,1,1] (39) 41-48.3-59 (61) × (10)10.5-12-15 (16) μm (Q = 3.1-5.0, Q* = 4.0), bisporic, narrowly to broadly clavate, hyaline in 5% KOH. Cheilocystidia [15,1,1] (49) 53-78.2-110 (118) × (8.7) 12-16.6-23 (26) µm, (Q = 2.9-6.6, Q* = 4.8), numerous, short-pedicellate, conical, fusiform, narrowly clavate, narrowly cylindrical, narrowly lageniform to lageniform, often clamped, smooth, thin-walled, hyaline in 5% KOH. Pleurocystidia [30,3,1] (71) 75-106.7-130 (132) × (24) 24.5-28.5-36 (37.5) µm (Q = 2.8-5.4, Q* = 3.8), fusiform, clavate, narrowly clavate, utriform, narrowly utriform, rounded apex, smooth, firm-walled, hyaline in 5% KOH. Hymenophoral trama irregular, made of thin-walled, hyaline hyphae. Pileipellis a hymeniderm; terminal elements (26.5)27-34.2-42(46) × (12)13-17-22(25.5) µm, with scattered intracellular light brown (6D8) pigment in 5% KOH. Stipitipellis an intricate trichoderm; hyphae (3.3)3.5-5.0-6.0(6.2) µm wide, hyaline in 5% KOH. Clamp connections not observed.

Habitat and distribution.

Solitary, on the soil covered with litter, in tropical hill forest of Chiang Mai Province, Thailand.

Specimen examined.

Thailand. Chiang Mai Province: Mae Taeng District, Ban Pa Daeng, elev. 1,110 m, tropical evergreen hill forest, 08 August, 2019, A.G. Niego, MFLU22-0142; GenBank OP265166-ITS, OP265161-nrLSU.

Notes.

The specimen described in this study is morphologically quite similar to H. orientalis , which was first described from Japan ( Petersen and Nagasawa 2006). However, it has a smaller pileus (15 mm diam.). It also produces 2-spored basidia whereas those of the holotype are 4-spored. The ITS genetic distances from the two most closely related H. orientalis TMI-2IX2002c1 and HKAS70323 were 2.57% and 1.30%, respectively. Such distances may be compatible with conspecificity. However, some morphological differences were noted, but based only on the single specimen we collected. Therefore, we use the name H. aff. orientalis until additional collections are available from tropical and temperate Asia to ascertain its taxonomic identity and properly describe it if it is confirmed to be a new species different from H. orientalis .

Figures

Figure 6. Basidioma of Hymenopellis aff. orientalis MFLU 22 - 0142 A top view B side view C view of lamellae D side view of context. Scale bar: 1.0 cm (A, D). Photographs by A. G. Niego.

Figure 7. Micromorphological features of Hymenopellis aff. orientalis MFLU 22 - 0142 A basidiospores B basidia C cheilocystidia D pleurocystidia E terminal elements of pileipellis F stipitipellis.