Nevesoporus nigrostipitatus
Nevesoporus nigrostipitatus A.C. Magnago 2022, in Magnago, et al., Mycologia 114, 607-625 (2022)
Etymology: nigrostipitatus (Latin), in reference to the blackish, shiny stipe.
Diagnosis: Differs from Tylopilus nigripes by the pinkish brown pileus, unchanging color of the hymenophore when bruised, and shorter, more ellipsoid basidiospores.
Pileus 11–32 mm broad, initially parabolic and velvety, with age convex to plano-convex and subareolate toward the margin, initially brown (OAC 635), light pinkish brown (OAC 638, OAC 646) with age, dry; margin straight. Hymenophore subdecurrent, slightly depressed around the stipe, off-white (OAC 816), pale pink (OAC 668) with age; tubes 3–7 mm long centrally; pores 1–2 mm wide, angular, occasionally sublamellate near stipe, unchanging with pressure. Stipe 18–28 × 3–5 mm, central, subequal, dark gray (OAC 901) to black (OAC 909), abruptly concolorous with tubes at extreme apex, subglabrous to velutinous, somewhat shiny, brittle. Context in the pileus off-white (OAC 816), unchanging, and blackish in the stipe. Odor and taste not obtained. Macrochemical reactions: 10% NH4OH on all surfaces negative. Basidiospores dark reddish brown in fresh deposit, 8– 10 × 4–5 μm (Qm = 1.95, n = 40, s = 3), ellipsoid, pale reddish tan, inamyloid, smooth, thin-walled. Basidia 24– 32 × 8–10 μm, clavate, hyaline, inamyloid, 4-sterigmate; sterigmata 3–6 μm long. Pleurocystidia and cheilocystidia similar in shape and size, 68–85 × 9–13 μm, mostly narrowly fusoid to slightly ventricose, occasionally with one or two septa, hyaline, infrequent. Hymenophoral trama phylloporoid to subboletoid; mediostratum hyphae 4–9 μm wide, light yellow; lateral stratum hyphae slightly differentiated, 3–8 μm wide, hyaline to faintly yellow. Pileipellis a trichodermial palisade of catenulate hyphae; terminal elements tapering to the apex or clavate, 12–19 × 8– 10 μm, light brown, inamyloid. Pileus trama interwoven; individual hyphae 5–12 μm wide, light yellow. Stipitipellis with discrete clusters of anticlinal, cylindrical to subclavate, brownish hyphae; terminal elements 4–7 μm wide; caulobasidia infrequent. Stipe trama longitudinally oriented, of parallel individual hyphae 3–10 μm wide, light brown. Clamp connections absent.
Index Fungorum Number: IF838704
Notes: Nevesoporus nigrostipitatus is recognized in the field by the small, pinkish brown velvety pileus that is subareolate near the margin, subdecurrent, pinkish tubes that are slightly depressed around the stipe and unchanging where bruised, and slender, equal, dark gray to blackish stipe. The species is similar to Tylopilus nigripes Barbosa- Silva & Wartchow from Paraíba State in northeast Brazil (Barbosa-Silva et al. 2020). Tylopilus nigripes has similarly small basidiomata and a blackish stipe but differs from N. nigrostipitatus by the dark brown pileus, whitish to pale vinaceous context, adnate pinkish hymenophore staining red to black, and longer, more subfusoid basidiospores (8.2–13 × 3.5–5 μm, Qm = 2.63). The morphological and geographic congruences with N. nigrostipitatus suggest that T. nigripes might be better placed in Nevesoporus, but molecular data of T. nigripes are currently lacking (Barbosa- Silva et al. 2020).
The Guyanese N. exiguus resembles N. nigrostipitatus by the small basidiomata and blackish stipe but differs from it by the dark olive-green to blackish pileus that darkens with handling, adnate, white to dull pink hymenophore that rapidly blackens, and longer, higher-Q basidiospores (10– 13 × 4–5 μm, Qm = 2.35) (Henkel 1999).
Nevesoporus nigrostipitatus is similar to the Malaysian species Boletus nanus, B. psittacinus, and B. coccineianus by the small pileus width (5–25 mm) and lack of a blackish bruising reaction (Corner 1972). Among these species, B. psittacinus is most similar to N. nigrostipitatus in pileus width and coloration, but it has golden, pruinose tube edges and a longer stipe (30–60 mm). All three of these taxa differ from N. nigrostipitatus in their villose stipe base with prominent yellow or white mycelial strands, as well as other morphological features. Among Congolian boletes described by Heinemann, none combine the characters of small size, white hymenophore, blackish stipe, and reddish brown basidiospores as seen in N. nigrostipitatus.
Figure 1. Nevesoporus nigrostipitatus. A–G. ACM 1330, holotype. H. MAN 389. A. Basidiospores. B. Basidia. C. Pleuro- and cheilocystidia. D. Pileipellis terminal elements. E. Stipitipellis. F–H. Basidiomata. Bars: A–D = 10 μm; E = 25 μm; F–H = 10 mm.
References:
Barbosa-Silva A., & Wartchow F., & Sulzbacher, M.A. (2020). Tylopilus nigripes sp. nov. (Boletaceae, Basidiomycota) from the Atlantic Forest of Brazil. Feddes Repertorium 131, 244–250.
Corner E.J.H. (1972). Boletus in Malaysia. Singapore, Singapore: Government Printer. p. 263.
Henkel T.W. (1999). New taxa and distribution records for Tylopilus from Dicymbe forests of Guyana. Mycologia 91, 655–665.
Magnago, A. C., & Alves-Silva, G., & Henkel, T. W., & da Silveira, R. M. B. (2022). New genera, species, and combinations of Boletaceae from Brazil and Guyana. Mycologia 114, 607-625.
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