Nigrellomyces aquaticus W. M. Zhang & Q. Y. Feng, 2025

Zhang, Wang-ming, Song, Xiao-yu, Xie, Wan-qing, Zhou, Xin-zhong, Lu, Juan & Feng, Qin-ying, 2025, Morphological and multi-gene phylogenetic analyses reveal Nigrellomyces gen. nov. and one new species in Pleurotheciaceae from China, MycoKeys 122, pp. 277-292 : 277-292

Nigrellomyces aquaticus W. M. Zhang & Q. Y. Feng sp. nov.

Fig. 2

Etymology.

“ aquaticus ’’ refers to the aquatic habitat of this fungus.

Holotype.

GZAAS 25-0660

Description.

Saprobic on decaying wood submerged in a freshwater stream. Asexual morph: Colonies superficial, effuse, hairy, brown to black, scattered, with glistening conidial masses at apex. Mycelium partly superficial, partly immersed, consisting of branched, septate, smooth, smooth-walled, hyaline to pale brown hyphae. Conidiophores macronematous, mononematous, solitary, erect, unbranched, multi-septate, straight, or flexuous, cylindrical, slightly constricted at septa, 146–364 × 4.5–8 μm x ̄ = 224 × 5.8 μm, n = 25), dark brown, becoming pale brown to brown towards the apex. Conidiogenous cells polyblastic, integrated, terminal or intercalary, sympodial proliferations, sometimes denticles, cylindrical, reniform, curved, and swollen at the apex, 8.5–28 × 4–6 μm x ̄ = 20 × 5.2 μm, n = 25), pale brown to brown. Conidia acrogenous, subglobose to globose, ovoid to obovoid, or ellipsoidal, aseptate, occasionally forming chains in water, guttulate, 7.5–12.5 × 5–8.5 μm x ̄ = 8.9 × 7 μm, n = 25), light brown or black, smooth-walled, sometimes have small apiculus at the base. Sexual morph: Undetermined.

Culture characteristics.

Conidia germinate on PDA within 17 hours, producing germ tubes from the conidial body. Colonies on PDA are irregular with a flat surface and undulate margin, reaching 38 cm in diameter after 41 days at room temperature (approximately 25 ° C), and are brown to dark brown on both the surface and reverse sides.

Material examined.

China • Guizhou Province, Guiyang City, Baiyun District, Changpo Ling National Forest Park , on rotting wood in a freshwater habitat, 15 March 2025, Wang-Ming Zhang, QX 13 ( GZAAS 25-0660 , holotype), ex-type living cultures GZCC 25-0630 ; • Ibid., QX 13.1 ( GZAAS 25-0661 , paratype), living culture GZCC 25-0631 .

Notes.

In our phylogenetic tree (Fig. 1 ), isolates ( GZCC 25-0630 and GZCC 25-0631 ) formed a sister clade to Neomonodictys aquatica ( KUNCC 21-10708 ) and N. muriformis ( MFLUCC 16-1136 ) with weak support. Nigrellomyces aquaticus ( GZAAS 25-0660 ) can be distinguished from Neomonodictys aquatica (KUN-HKAS 115806) and N. muriformis ( MFLU 17-1178 ) by its longer conidiophores, elongated, polyblastic conidiogenous cells, and aseptate conidia ( Hyde et al. 2020; Huang et al. 2022). Moreover, base pair comparison of Nigrellomyces aquaticus ( GZCC 25-0630 ) and N. muriformis ( MFLUCC 16-1136 ) shows 96 / 588 bp differences in ITS (16.3 %, gaps 37 bp) and 22 / 829 bp differences in LSU (2.7 %, gap one bp). Therefore, based on multigene phylogenetic analysis and morphological differences, we introduce Nigrellomyces aquaticus as a novel genus and species.

Figures

Figure 1. Phylogenetic tree generated from ML analysis based on the combined LSU, ITS, SSU, and rpb 2 sequence data. Bootstrap support values for maximum likelihood greater than 75 % (ML left) and Bayesian posterior probabilities ≥ 0.95 (BYPP right) are shown at the nodes. The tree was rooted with Conioscypha lignicola (CBS 335.93) and C. minutispora (CBS 137253). Ex-type strains are denoted with “ T, ” and newly isolated strains are in bold red fonts.

Figure 2. Nigrellomyces aquaticus (GZAAS 25-0660, holotype). a, b. Colonies on the host surface; c – f. Conidiophores, conidiogenous cells, and conidia; g – h. Conidiogenous cells; i-j. Conidiogenous cells and conidia; k. Germinated conidium; l – o. Conidia; p, q. Colonies on PDA from above and below after 41 days of incubation at room temperature. Scale bars: 60 μm (d – f); 50 μm (c); 20 μm (g – j); 10 μm (k – o).