Pleurotus rickii Bres., Annales Mycologici, 1920

Bittencourt, Felipe, Drewinski, Mariana De Paula, Jr, Nelson Menolli & Drechsler-Santos, Elisandro Ricardo, 2024, Rare Pleurotus species with veiled basidiomata from the Neotropics: neotypification of Pleurotus magnificus and epityfication of Pleurotus rickii, Phytotaxa 672 (1), pp. 30-48 : 39-41

Pleurotus rickii Bres., Annales Mycologici 18(1-3): 27. (1920). Figs 5 , 6

Lectotype (designated here, MBT 10022150):— BRAZIL. Rio Grande do Sul: São Leopoldo, ad ligna, J. Rick 135 (S-F180929 [photograph!]) ( Fig. 6 A-B).

Epitype (designated here, MBT10022152):— BRAZIL. Santa Catarina: Florianópolis, Unidade de Conservação Ambiental Desterro (UCAD), 27°31’52’’S, 48°30’45’’W, on dead fallen trunk, 8 September 2017, F. Bittencourt, G.F.A. Flores, G. Scheibler & T. Kossmann 916 (FLOR 79342!).

Specimens examined:— BRAZIL. Santa Catarina:Florianópolis,Unidade de Conservação Ambiental Desterro (UCAD), 27°31’52’’S, 48°30’45’’W, on dead fallen trunk, 8 September 2017, F. Bittencourt, G.F.A. Flores, G. Scheibler & T. Kossmann 916 (FLOR 79342). Rio Grande do Sul: São Leopoldo, in wood, trunk, subcespitose (in ligna, ad truncos, subcaespitosus), 1905, J. Rick 363 (S-F180930) (original syntype) [photograph, Fig. 6C–D ].

Description:— Basidiomata gregarious to scattered ( Fig. 5A ), rarely solitary. Pileus narrowly to broadly-shallowly depressed, 43–129 mm diam.; surface greyish-brown (2C3) when fresh, dark grayish-yellow (5D5) when dry, on young specimens with scattered minute squamules more abundant towards the center, in mature specimens with only a few remaining in the center, wrinkled when dry; margin brighter, incurved when young, involute at maturity; context up to 8 mm wide near the pileus center, white (1A1) to yellow when dry. Lamellae deeply decurrent, close, narrow, white to pale yellow (5A1) when fresh, brownish-yellow (5C7) in dried specimens; lamellar edges entire and concolorous; lamellulae present, 1–3 tiers. Partial veil present in young basidiomata, fugacious, single, pale yellow (5A1), leaving remnants on the pileus surface ( Fig. 5B ), annulus not seen. Stipe central to subeccentric, fleshy fibrous, solid, cylindrical to slightly attenuated upward, pale yellowish brown (2E 4, 6E 5), 16–27 mm long, 4–12 mm thick, with dark scales along it more easily seen on dried specimens, whitish mycelium present in the base ( Fig. 5C ).

Basidiospores [20/1/1] (8.3–)8.7–13.2(–14.1) × (2.8–)3.1–4.6 µm (avg. = 10.5 × 3.9 µm), Q = 2.1–3.5, Qm = 2.7, IKI- (n=20), cylindrical to bacilliform, smooth, thin-walled, often bearing one or two guttules ( Fig. 5F ). Basidia (26–)27–40(–44) × 5.5–7.0 µm, cylindrical-clavate, hyaline, thin-walled, 4-sterigmate, with a basal clamp. Pleurocystidia and cheilocystidia absent. Hyphal system dimitic with clamp connections. Lamellar trama irregular, generative hyphae hyaline, frequently branched, sometimes very inflated, thin- to slightly thick-walled (up to 1 µm thick), 3.0–11.0(–15.0) µm diam., skeletal hyphae aseptate, rarely branched, hyaline, thick-walled (up to 1.0 µm thick). Subhymenium well developed, 24–46 µm wide, with pseudoparenchymatous, isodiametric, hyaline cells, (2.5–)3.0–7.0(–7.8) µm wide ( Fig. 5D ). Pileipellis a cutis, 15–90 µm wide, composed of generative hyphae repent to radially arranged, yellowish to brownish, thin- to slightly thick-walled (up to 0.5 µm thick), (1.9–)3.0–5.5(–5.8) µm diam., sometimes with individual cylindrical hyphae or hyphal bundles projecting up to 30 µm upwards; skeletal hyphae rare, 3.2–4.8 µm diam. ( Fig. 5E ). Pileus hyphal system composed of irregularly arranged thin- to slightly thick-walled (up to 1.0 µm thick), colorless and hyaline, generative hyphae (2.1–)2.3–12.8(–13.5) µm diam.; skeletal hyphae aseptate, rarely branched, hyaline, thick-walled (up to 2.0 µm thick), (2.6–)2.8–5.4 µm diam. Stipitipellis similar to pileipellis, composed of generative hyphae 2.5–5.0(–6.0) µm diam., skeletal hyphae (1.5–)2.0–4.0(–5.0) µm diam. Stipe hyphal system composed of irregularly arranged thin- to slightly thick-walled (up to 1.0 µm thick), colorless and hyaline, generative hyphae, 2–8 µm diam.; skeletal hyphae aseptate, rarely branched, hyaline, thick-walled (up to 1.0 µm), 2.5–6.0 µm diam.

Ecology and distribution:—On dead trunks of unidentified angiosperms in tropical and subtropical forests. Recorded for Argentina (Yungas province, Lechner et al. 2004) and Brazil, where it is known for the states of Rio Grande do Sul ( Rick 1907, 1937, 1961, Bresadola 1920), Santa Catarina (present work), and São Paulo ( Menolli et al. 2014), in the Southern and Southeastern regions of Brazil (Atlantic Forest and Pampean provinces) ( Fig. 1 ).

Figures

FIGURE 1. Distribution map of Pleurotus magnificus (blue points) and P. rickii (red points) in South America. Colored areas are delimitations of biogeographic provinces according to Morrone (2014).

FIGURE 5. Morphological features of Pleurotus rickii (FLOR 79342, epitype).A. Habit; B. Pileus surface, showing the minute squamules and partial veil remnants (white arrows); C. Detail of the basal mycelium at the stipe; D. Hymenium, subhymenium and part of trama; E. Pileipellis; F. Basidiospores. Scale bars: A, B, C: 2 cm; D, E, F = 10 µm. All photos and illustrations by F. Bittencourt.

FIGURE 6. Pleurotus rickii syntypes at S herbarium. A: S-F180929 (Rick 135, designated here as lectotype); B: Rick’s original notes of S-F180929; C: S-F180930 (Rick 263); D: Rick’s original notes of S-F180930. Photos provided by the © Swedish Museum of Natural History, Stockholm; image reproduced with permission.