Hydropus globosporus A. C. Cooper, Desjardin & B. A. Perry 2018, spec. nov.
Creators: name: Cooper, Alexandra C.
name: Desjardin, Dennis E.
name: Perry, Brian A.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Agaricales
Marasmiaceae
Hydropus
Hydropus globosporus

description: 17. Hydropus globosporus A.C. Cooper, Desjardin & B.A. Perry, spec. nov. (Figs. 30, 31)   
MycoBank no.: MB 825517  
Holotype:—AFRICA. São Tomé, Macambrara radio antenna area, above 1300 meters, N00˚16.557’, E06˚36.326’, 25 April 2008, D.E. Desjardin and B.A. Perry, BAP 661 (SFSU).  
 Etymology:— globus (L.) – ball; spora (Gr.) – to sow, spore; referring to the globose basidiospores.   
 Diagnosis:— Pileus 5–11 mm diam, hemispherical with flattened apex to convex, centrally depressed to umbilicate, striate to sulcate; surface glabrous, moist, brown to dark brown (6E–F4–5) when young, fading to greyish brown (4–5E4–5) in age, central depression remaining dark. Context thin, white. Lamellae adnate with decurrent tooth to decurrent, distant (9–11) with 1–2 series of lamellulae, broad (up to 4 mm), non-intervenose, white, with concolorous edge. Stipe 6–10 × 0.75–1.5 mm, central, terete, tapered towards base, hollow; surface minutely pruinose, with white pruinae at apex and dark brown pruinae below, otherwise white, developing greyish brown tones towards the base. Basidiomata not blackening. Odour indistinct; taste not recorded. Bioluminescence undetected.   
 Basidiospores (4.8–) 5.6–7.2 (–8.0) × (4.8–) 5.6–6.4 μm [x m = 6.04 ± 0.73 × 5.67 ± 0.42 μm, Q = 0.86–1.25, Q m = 1.06 ± 0.07, n = 25, s = 1], globose to subglobose with a prominent apiculus, smooth, hyaline, inamyloid, thin-walled. Basidia 18.4–21 × 4.8–5.6 μm, clavate, hyaline, inamyloid, thin-walled, 2-spored, rarely 3-spored, sterigmata up to 7.2 μm long. Basidioles clavate. Lamellar edge sterile. Cheilocystidia 42–66 × 8.4–10 μm, subclavate to cylindrical, non-spinulose, hyaline, inamyloid, thin-walled. Pleurocystidia common, 30–40 (–62) × 6.5–9 μm, similar to cheilocystidia. Pileipellis a cutis; hyphae 4–10 μm diam, cylindrical to inflated, smooth, hyaline or with contents brown, inamyloid, thin-walled; terminal cells undifferentiated of seldom clavate, repent to suberect. Hypodermium undifferentiated. Pileus trama hyphae 6–28 μm diam, cylindrical to inflated, with brown contents, inamyloid, thin-walled. Hymenophoral trama regular to subregular; hyphae 3–20 (–32) μm diam, cylindrical to inflated, hyaline, inamyloid, non-gelatinous, thin-walled. Stipitipellis a cutis with caulocystidia; cortical hyphae 3.2–4.8 μm diam, parallel, cylindrical, smooth, hyaline, inamyloid, thin-walled; medullary hyphae 7.2–18 μm diam, smooth, inamyloid to weakly dextrinoid, thin-walled. Caulocystidia abundant; 8–38 × 6.4–13 μm, cylindrical to subclavate or geniculate, few intercalary, non-spinulose, hyaline or occasionally with brown contents, inamyloid, thin-walled. Clamp connections present in all tissues.   
Habitat and known distribution:—Gregarious on decaying wood in secondary upland forest. (São Tomé). Only known from the holotype.  
 Notes:— Hydropus globosporus is distinguished by small basidiomata with brown, sulcate, convex-umbilicate pileus, distant, broad, subdecurrent white lamellae, a white, brown-pruinose stipe, inamyloid, globose to subglobose basidiospores with mean 6 × 5.7 μm, 2-spored basidia, subclavate to cylindrical cheilocystidia and caulocystidia, a cutis-type pileipellis of smooth hyphae with brown cytoplasmic contents, cylindrical to geniculate, hyaline or brown caulocystidia, and lignicolous habit. In combination, these features indicate placement in sect. Floccipedes subsect. Floccipedes. Within this infrageneric group, the globose basidiospores suggest our São Tomé material is close to the north temperate H. floccipes (Fr.) Singer, however the latter species forms campanulate-subumbonate to convexpapillate pilei, adnate to adnexed, close to crowded lamellae, much longer stipes, 4-spored basidia, more ampullaceous hymenial cystidia (20–100 × 7–15 μm), and differentiated pileipellis terminal cells (Singer 1982, Laessøe 2008). Corner (1966) accepted numerous Hydropus in the genus Trogia. If keyed there, H. globosporus comes closest to T. mycenoides Corner, but the latter forms a conical pileus, adnexed, subclose (17–22) lamellae, ellipsoid basidiospores (6–8 × 4–5 μm), 4-spored basidia, and ventricose hymenial cystidia (Corner 1966).   
 Pairwise comparisons of aligned, overlapping ITS sequences of H. globosporus (BAP 661) with the top ten BLAST results indicate 87.4–89.2% similarity to several undetermined Agaricales. The closest determined species was H. funebris (Speg.) Singer, with 87.1% similarity, and the two species are sister in the ITS phylogeny (Fig. 3) with high support (100% BS, 1.0 PP). ITS sequences of H. fuliginarius (Batsch) Singer, type species of Hydropus, are unavailable for comparison.
description: Published as part of Cooper, Alexandra C., Desjardin, Dennis E. & Perry, Brian A., 2018, The genus Mycena (Basidiomycota, Agaricales, Mycenaceae) and allied genera from Republic of São Tomé and Príncipe, West Africa, pp. 1-47 in Phytotaxa 383 (1) on pages 39-40, DOI: 10.11646/phytotaxa.383.1.1, http://zenodo.org/record/13724481