Neohelicomyces terrestris T. H. Tan & J. Ma, 2025

Neohelicomyces terrestris T. H. Tan & J. Ma sp. nov.

Fig. 2 View Figure 2

Etymology.

The species epithet “ terrestris ’’ refers to the terrestrial habitat of this fungus.

Holotype.

HKAS 128950 .

Description.

Saprobic on decaying wood in a terrestrial habitat. Sexual morph Undetermined. Asexual morph Hyphomycetous, helicosporous. Colonies on natural substrate superficial, effuse, gregarious, with masses of crowded, glistening conidia, white to brown. Mycelium partly immersed, partly superficial, composed of hyaline to pale brown, branched, septate, smooth hyphae. Conidiophores 106–212 × 3–4.5 μm (x ̄ = 176 × 4 μm, n = 25), macronematous, mononematous, erect, cylindrical, flexuous, widest at the base, tapering towards narrow apex, branched or unbranched, septate, brown at base, subhyaline towards apex, thick-walled. Conidiogenous cells 7.5–25 × 2–4 μm (x ̄ = 13.5 × 3.5 μm, n = 25), holoblastic, monoblastic, or polyblastic, integrated, terminal or intercalary, cylindrical, with denticles, subhyaline to pale brown, smooth-walled. Conidia solitary, acropleurogenous, helicoid, developing on tooth-like protrusion, 15–21 μm diam. and conidial filament 2.5–3.5 μm wide (x ̄ = 17.5 × 3 μm, n = 20), 107–143 μm long (x ̄ = 128.5 μm, n = 30), loosely coiled 2 1 / 2 –3 times, becoming loosely coiled in water, septate, guttulate, hyaline, smooth-walled.

Culture characteristics.

Conidia germinated on PDA and produced germ tubes within 11 h. Colonies on PDA reached 27 mm in diameter after 40 days of incubation at 25 ° C, with an irregular shape, raised surface, and undulate margin, pale brown to brown; the reverse was brown to dark brown.

Material examined.

China • Hainan Province, Wuzhishan City, Shuimanhe tropical rainforest scenic area in Wuzhishan , 18°92′N, 109°63′E, on decaying wood in a terrestrial habitat, 4 November 2024, Ting-Hong Tan & Jian Ma, WZ 66 ( HKAS 128950 , holotype), ex-type living cultures GZCC 23-0399 • ibid., WZ 67 ( GZAAS 23-0403 , paratype), living culture GZCC 25-0660 .

Notes.

Morphologically, Neohelicomyces terrestris ( HKAS 128950 ) resembles Parahelicomyces laxisporus ( HKAS 128943 ) in having macronematous, mononematous, erect, widest-at-the-base, tapering-towards-a-narrow-apex, brown-at-base, subhyaline-towards-apex, flexuous conidiophores; holoblastic, monoblastic or polyblastic, integrated, cylindrical conidiogenous cells with denticles, subhyaline to pale brown; and acropleurogenous, helicoid, aseptate, guttulate, hyaline conidia ( Ma et al. 2024 b). However, N. terrestris ( HKAS 128950 ) differs from Pa. laxisporus ( HKAS 128943 ) by its wider conidial diameter (up to 21 μm vs. 14.5–16 μm) and longer conidia (up to 143 μm vs. 80.5–124 μm) ( Ma et al. 2024 b). Phylogenetically, our isolates ( GZCC 23-0399 and GZCC 25-0660 ) form a sister clade to N. wuzhishanensis ( GZCC 23-0410 ), with 87 % ML and 1.00 BYPP support (Fig. 1 View Figure 1 ). Comparison of the LSU, ITS, tef 1 - α, and rpb 2 sequence data between Neohelicomyces terrestris ( GZCC 23-0399 ) and N. wuzhishanensis ( GZCC 23-0410 ) revealed nucleotide base differences of 5 / 486 bp (1 %, including three gaps), 26 / 484 bp (5.4 %, including 10 gaps), 25 / 937 bp (2.7 %, including seven gaps), and 33 / 926 bp (3.6 %, with no gaps), respectively. Therefore, based on both multi-gene phylogenetic analyses and morphological differences, we introduce Neohelicomyces terrestris as a novel species.