Neohelicosporium irregulare Y.Z. Lu, J.C. Kang & K.D. Hyde
Index Fungorum number: IF 554871; Facesoffungi number: FoF 04739
Holotype: MFLU 17–1095
Etymology: “irregulare” referring to irregular conidiophores of this fungus.
Saprobic on decaying wood in a freshwater stream. Sexual morph: Undetermined. Asexual morph: Hyphomycetous, helicosporous. Colonies on the substratum superficial, effuse, gregarious, white. Mycelium composed of partly immersed, partly superficial, hyaline to pale brown, septate, branched hyphae, with masses of crowded, glistening conidia. Conidiophores macronematous, mononematous, cylindrical, mostly unbranched, occasionally branched, septate, exist two kinds of length, the longer one 90–265 μm long, 4–6 μm wide at bottom, tapering to 1–2 μm wide at apex, the shorter one 35–55 μm long, 4.5–7 μm wide, pale brown to brown, smooth-walled. Conidiogenous cells holoblastic, mono- to polyblastic, integrated, sympodial, terminal or intercalary, cylindrical, with denticles, some of them are arising laterally from the conidiophores as tiny bladder-like protrusions, 12–22 μm long, 3–5.5 μm wide, pale brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, rounded at tip, 25–40 μm diam. and conidial filament 3.5–4.5 μm wide (x̄ = 32 × 4 μm, n = 20), 150–270 μm long, coiled 1½–2 times (coiled 3–4 times in paratype MFLU 17–1117), becoming loosely coiled or uncoiled in water, indistinctly multi-septate, guttulate, hyaline, smooth-walled. (Description from Lu et al. 2018)
Culture characteristics: Conidia germinating on water agar and germ tubes produced from conidia within 12 h. Colonies growing on MEA, irregular, with flat surface, edge undulate, reaching 19 mm in 4 weeks at 28 °C, brown to dark brown in MEA medium. Mycelium superficial and partially immersed, branched, septate, hyaline to pale brown, smooth.
Material examined: THAILAND, Chiang Rai, Muang, Ban Nang Lae Nai, on submerged decaying wood in a freshwater stream, 31 December 2016, Yong-Zhong Lu, CR12–2 (MFLU 17–1095, holotype; HKAS 100765, isotype), ex-type living cultures, MFLUCC 17–1796, TBRC 8906; THAILAND, Chiang Mai, Mae Taeng, Mushroom Research Center, on decaying wood in a mountain, 25 January 2017, Yong-Zhong Lu, MRC18 (MFLU 17–1117, paratype), living culture, MFLUCC 17–1808.
Notes: Two isolates of Neohelicosporium irregulare were collected from different habitats (the holotype MFLU 17–1095 was from aquatic habitat and the paratype MFLU 17–1117 was from terrestrial habitat). It is necessary to point out that their conidiophores are irregular, there are long and short conidiophores that coexist in both of them. The conidiogenous cells of MFLU 17–1095 are also irregular, most of them are denticulate protrusions but some are tiny bladder-like protrusions. The conidia of MFLU 17–1095 has only 1½–2 coils but MFLU 17–1117 are coiled 3–4 times and become loose in water. However, our multi-gene phylogenetic analyses show that these two isolates should be the same species given that they cluster together. We also compared their nucleotides, and there are only 1, 1, 1, 3 base pairs differences in their ITS, LSU, RPB2 and TEF1α respectively, which also indicate that they are the same species. Therefore, despite having slightly different morphs pertaining to the number of coils, we identified them as the same species. (Notes from Lu et al. 2018)
Freshwater distribution: Thailand (Lu et al. 2018)