Neomyrmecridium triseptatum W.P. Wang & Z.L. Luo, in Cao et al., Fungal Diversity 132: 499 (2025)
Index Fungorum number: IF 572040; MycoBank number: MB 5702040; Facesoffungi: FoF 16386; Figs. 1, 2
Etymology – Referring to the conidia with three septate.
Holotype – HKAS 136944.
Saprobic on submerged decaying wood. Asexual morph: Colonies on natural substrate superficial, scattered, solitary or gathered, brown to brownish-yellow, hairy. Mycelium mostly immersed, composed of septate, smooth-walled, hyaline to brown hyphae. Conidiophores (144–)204–332 × 3.4–4.8 µm (x̄ = 253.7 × 4.2 µm, n = 20), macronematous, mononematous, erect, unbranched or branched, slightly flexuous to curved, cylindrical, with irregular contraction and then curved, septate, brown, paler towards the apex, subhyaline to pale brown at the apex, with multiple denticulate conidiogenous loci at the upper part. Conidiogenous cells polyblastic, integrated, terminal, becoming intercalary, sympodial, short, pimple-like denticles. Conidia 16–23 × 3.7–5.6 µm (x̄ = 18.7 × 4.7 µm, n = 40), solitary, clavate to fusiform, truncate at the base, subhyaline to pale brown, 3-septate when mature without septum, verrucose, tapering to the base with a hilum, with a thin mucilaginous sheath at the middle part (Fig. 2j, l). Sexual morph: Undetermined.
Culture characteristics – Conidia germinating on PDA within 12 h, and germ tubes produced from both ends. Colonies growing on PDA, and after 3 weeks of incubation at room temperature, the diameter reaches about 2 cm. Mycelia damp, dense, colonies on the surface of PDA, thin, with a punctate protrusion in central, surface flat, with regular edges, yellow. Reverse circular, brownish-yellow to yellow with pale yellow edges, smooth.
Material examined – CHINA, Yunnan Province, Qujing City, Luoping County, Jiulonghe River (24°92’51.39″N 104°28’78.54″E), on submerged decaying stem of unknow species of Bambusoideae, 15 July 2023, Wen-Peng Wang, S-5133 and S-5134 (HKAS 136944, holotype; KUNCC 23–15,577, ex-type).
GenBank – KUNCC 23–15577: PQ143313 (ITS), PQ143315 (LSU).
Notes – Neomyrmecridium triseptatum matches the concept of Neomyrmecridium in having erect, cylindrical conidiophores paler towards the apex, polyblastic conidiogenous cells bearing multiple denticles at upper part, and clavate to fusiform conidia with 3-septate when mature (Crous et al. 2018; Hyde et al. 2020a; Serrano et al. 2020; Xu et al. 2023; Yang et al. 2023a). However, N. triseptatum has unbranched or branched conidiophores with irregular contraction and then curved, this feature can be easily distinguished from other species of Neomyrmecridium. In the phylogenetic analysis, N. triseptatum constitutes an independent lineage that are basal to other Neomyrmecridium species (Fig. 1). We therefore identify Neomyrmecridium triseptatum as a new species based on morphological and phylogenetic analysis.
Figure 1 – Maximum Likelihood tree based on ITS and LSU sequences date. Bootstrap support values for ML greater than 70% and Bayesian posterior probabilities (PP) greater than 0.95 are given as ML/P above the nodes. Newly obtained sequences are indicated in red and ex-type strains are in bold.
Figure 2 – Neomyrmecridium triseptatum (HKAS 136944, holotype). a, b Colonies on the substratum. c Conidiophore. d, e Conidiophores and conidia. f Denticulate conidiogenous loci. g, h Conidiogenous cells with conidia. i–l Conidia. m Germinating conidium. n, o Colonies on PDA from surface and reverse. Scale bars: c–e = 40 µm, f–h, m = 10 µm, i–l = 5 µm.