Pseudohelicomyces aquaticus Y.Z. Lu, Boonmee & K.D. Hyde
Index Fungorum number: IF 554887; Facesoffungi number: FoF 04746
Holotype: MFLU 17–1183
Etymology: “aquaticus” referring to aquatic habitat.
Saprobic on decaying wood in a freshwater stream. Sexual morph: Undetermined. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, white to pale brown. Mycelium composed of partly immersed, partly superficial, hyaline to pale brown, septate, branched hyphae, with masses of crowded, glistening conidia. Conidiophores macronematous, mononematous, cylindrical, branched, ramose, septate, 50–170 μm long, 3.5–5 μm wide, hyaline to brown, smooth-walled. Conidiogenous cells holoblastic, mono- to polyblastic, integrated, sympodial, terminal or intercalary, cylindrical, truncate at apex after conidial secession, 8–16 μm long, 2.5–4.5 μm wide, hyaline to pale brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, rounded at tip, 15–20 μm diam. and conidial filament 1.5–3 μm wide (x̄ = 17 × 2 μm, n = 20), 90–130 μm long, indistinctly multi-septate, coiled 2½–3½ times, becoming loosely coiled in water, guttulate, hyaline to pale brown, smooth-walled. (Lu et al. 2018)
Culture characteristics: Conidia germinating on water agar and germ tubes produced from conidia within 12 h. Colonies growing on PDA, circular, with flat surface, edge undulate, reaching 19 mm in 3 weeks at 28 °C, brown to dark brown in PDA medium. Mycelium superficial and partially immersed, branched, septate, hyaline to pale brown, smooth.
Material examined: THAILAND, Krabi, Muang, Khao Khram, Ban Nong Jig, Tha Pom Klong Song Nam, on submerged decaying wood in freshwater stream, 16 December 2015, Saranyaphat Boonmee, TP01–1 (MFLU 17–1183, holotype), ex-type living cultures, MFLUCC 16–0234, TBRC 8903.
Notes: Morphologically, Pseudohelicomyces aquaticus is similar to Neohelicosporium parvisporum (Lu et al. 2018) in conidia but can be distinguished by conidiophores and conidiogenous cells. The conidiophores of N. parvisporum are hyphae-like with many tiny denticles arising laterally as sporogenous conidiogenous loci, but P. aquaticus lacks these characteristics. The conidiogenous cells of P. aquaticus are terminal or intercalary, with an irregular-cylindrical shape, truncate at apex after conidial secession. Besides, the conidia of P. aquaticus are acropleurogenous, but those of N. parvisporum are pleurogenous. Furthermore, H. aquaticus differs from Helicomyces species in having obviously smaller conidia as well as an irregular-cylindrical shaped conidiogenous cells. Phylogenetically, P. aquaticus constitutes a well-supported independent lineage within Pseudohelicomyces and support it as a distinct species. (Notes from Lu et al. 2018)
Freshwater distribution: Thailand (Lu et al. 2018)
Fig 1 Pseudohelicomyces aquaticus (MFLU 17–1183, holotype). a Colony on decaying wood. b–d Conidiophores. e–h Conidiogenous cells. i–l Conidia. m, n Colonies on PDA from above and below. Scale bars: a = 100 µm, b = 50 µm, c, d = 20 µm, e–l = 10 µm (Lu et al. 2018)
Lu YZ, Liu JK (Jack), Hyde KD, Jeewon R, Kang JC, Fan C, Boonmee S, Bhat DJ, Luo ZL, Lin CG, Eungwanichayapant PD (2018) A taxonomic reassessment of Tubeufiales based on multi-locus phylogeny and morphology. Fungal Divers 92:131–344. https://doi.org/10.1007/s13225-018-0411-y