Hymenoporus paradoxus

Hymenoporus paradoxus Tkalčec, Mešić & Chun Y. Deng, in Tkalčec et al., Phytotaxa 204(3): 205 (2015)

Etymology: The species is named for its basidiocarps which are odd-looking for the family Omphalotaceae.

Diagnosis: Differs from all other marasmioid species by a true tubular (poroid) hymenophore and from other tubular agarics by a free collarium and central, tough, dark and filiform stipe. Pileus hemispherical to convex, furfuraceous, whitish to light brown, up to 3 mm broad. Hymenophore tubular, broadly adnate to a free collarium, whitish to pale brown. Stipe tough, filiform, insititious, dark brown to black, up to 52 × 0.4 mm. Spores 6.2–7.3 × 3.6–4.8 μm, ellipsoid to elongated, smooth, hyaline, non-amyloid. Basidia 4-spored. Basidioles fusoid to clavate, apex mostly mucronate to rostrate. Cheilocystidia densely packed, dendriform, body hyphoid and branched, with dense, coralloid terminal parts. Pleurocystidia sparse, irregularly clavate with apical simple to coralloid projections. Pileipellis composed of repent hyphae, densely covered with simple to coralloid excrescences, at places intermixed or replaced with dendriform cells similar to cheilocystidia. Caulocystidia absent. Clamp connections abundant.

Pileus 0.7–3 mm broad, hemispherical at first, then convex or plano-convex, often with deflexed margin, sulcate at margin, not hygrophanous, pinkish- or sordid-white to light brown with a darker, light brown to brown central zone, dried becomes grayish, surface dull, dry, furfuraceous. Hymenophore tubular (poroid), broadly adnate to a free collarium, tubes ≤1 mm long, pale brown, pores 0.1–0.2 mm in diameter, isodiametric to elongate, along the edge often larger or more elongated (≤0.3 mm), pinkish to sordid white, sometimes pale brown, (1–)2–5 pores between stipe and the pileus edge, situated at the same level. Stipe 7–52 × 0.1–0.4 mm, filiform, tough, dry, hollow, insititious, dark brown to black, mostly covered with scattered to dense concolorous small pustules (more abundant at stipe apex). Sterile stipes (telepods) present. Context pale brown to brown in the pileus, concolorous with the surface of the stipe. Smell and taste not recorded.

Basidiospores [17/3/1] 6.2–7.0–7.3 × 3.6–4.1–4.8 μm, Q = 1.50–1.72–1.80, ellipsoid to elongated, in side view slightly amygdaliform, smooth, hyaline, thin-walled, non-amyloid, non-dextrinoid. Basidia 15–31 × 6.5–10 μm, clavate, apex mostly mucronate, 4-spored, thin-walled, hyaline, clamped, sterigmata up to 6 μm long. Basidioles subcylindrical at first, soon becoming fusoid, finally clavate, apex mostly mucronate to rostrate (extension up to 4 μm long). Pore edge sterile, covered with densely packed cheilocystidia. Cheilocystidia up to ca. 60 × 45 μm, dendriform, main body hyphoid (hyphae 1–4 μm wide), branched, thin- to moderately thick-walled (up to 0.8 μm), with dense, hyaline, coralloid terminal parts (apical projections 0.5–4 μm long). Pleurocystidia sparse, more abundant near the pores, 10–25 × 5–13 μm, irregularly clavate with apical simple to coralloid projections (0.5–3 μm long), thin-walled, hyaline. Hymenophoral trama subregular, composed of 1.5–7(–10) μm broad, thin- to thick-walled (up to 2 μm thick), subhyaline to brown, smooth to coarsely incrusted hyphae. Pileipellis composed of repent, thin-walled, hyaline (rarely brown), 2–10 μm wide hyphae, mostly densely covered with hyaline, simple to coralloid excrescences (less often excrescences are sparse or hyphae ± smooth), at places intermixed or replaced with branched, dendriform cells (similar to cheilocystidia) with hyaline, coralloid terminal parts; apical projections 0.5–3(–4.5) × 0.5–0.7 μm. Pileal trama composed of loosely interwoven, frequently branched, subhyaline to brown (pigment more abundant beneath the pileipellis), mostly thick-walled (up to 4(–6) μm thick), 3–10(–20) μm broad hyphae, walls mostly heavily incrusted (rarely smooth). Stipitipellis a cutis of parallel, densely packed, cylindrical, thin- to thick-walled (up to 1.5 μm thick), 1.5–6 μm broad, red- or gray-brown (sometimes subhyaline) hyphae, with a glabrous, uneven, slightly diverticulate or incrusted surface, pigment intracellular, parietal or sometimes incrusted, with irregular, red- to gray-brown, heap-like excrescences, primarily in the apex of stipe. Caulocystidia absent. Stipe trama composed of parallel, thin- to thickwalled (up to 2 μm thick), 1.5–10 μm broad, subhyaline to red- or gray-brown, glabrous to coarsely encrusted (near cavity of the stipe), sometimes slightly diverticulate hyphae. Clamp connections present and abundant in all tissues. Chemical reactions: all parts of basidiocarp non-amyloid and non-dextrinoid except pileipellis that can sometimes be partially amyloid (violet in Melzer’s reagent).

Habitat: Broad-leaved forest with bamboo, along the road, on fallen leaves of broad-leaved trees. Distribution: Known only from the type locality in China

Index fungorum number: IF805767

Notes: Morphologically, Hymenoporus paradoxus is characterized by a small, hemispherical to convex, whitish to light brown pileus, a true tubular (poroid), whitish to light brown hymenophore which is broadly adnate to a free collarium, a tough, filiform, insititious, dark brown to black stipe, ellipsoid to elongated, hyaline, non-amyloid spores (6.2–7.3 × 3.6–4.8 μm), fusoid to clavate basidioles with a mucronate to rostrate apex, densely packed, dendriform cheilocystidia with a hyphoid, branched body and dense, coralloid terminal parts, and a pileipellis composed of repent hyphae, densely covered with simple to coralloid excrescences, at places intermixed or replaced with dendriform cells similar to cheilocystidia. Although morphological characters of the specimen clearly show that it belongs to a new species, molecular phylogenetic analysis was needed to ascertain its phylogenetic position among marasmioid fungi. The BLAST search in GenBank using the partial 28S rDNA gave a maximum of 89% match with sequences of a fair number of species belonging to the family Omphalotaceae (mostly from the genus Gymnopus). Its affiliation to the Omphalotaceae is confirmed by the phylogenetic analysis.

Figure 1. Hymenoporus paradoxus. A–C. Fresh basidiocarps. Scale bars: A = 5 mm; B = 3 mm; C = 1 mm. Photo C.-Y. Deng.