Absidia simplex Z. Y. Ding, Yang Jiang, Yi Xin Wang & X. Y. Liu, 2025

Ding, Zi-Ying, Ji, Xin-Yu, Tao, Meng-Fei, Jiang, Yang, Liu, Wen-Xiu, Wang, Yi-Xin, Meng, Zhe & Liu, Xiao-Yong, 2025, Unveiling species diversity within early-diverging fungi from China IV: Four new species of Absidia (Cunninghamellaceae, Mucoromycota), MycoKeys 119, pp. 29-46 : 29-46

Absidia simplex Z. Y. Ding, Yang Jiang, Yi Xin Wang & X. Y. Liu sp. nov.

Fig. 3

Type.

China • Yunnan Province, Longling County, Mengnuo Town (24°31'25"N, 99°00'42"E, altitude 1319.65 m), from a soil sample, 8 July 2024, Z. Y. Ding and X. Y. Liu, holotype HMAS 353364 , ex-holotype living culture CGMCC 3.28541 (= XG 10012-9) .

Etymology.

The epithet simplex (Lat.) refers to the simple branching pattern of sporangiophores.

Description.

Hyphae branched, hyaline when young, light brownish when old, aseptate initially, septate with age. Stolons branched, smooth, hyaline, brownish, septate, 2.5–10.0 µm in diameter. Rhizoids finger-like, hyaline, poorly developed, mostly unbranched, occasionally simply branched. Sporangiophores arising from stolons, erect or slightly bent, commonly monopodial, unbranched or branched 1–2 times, never in whorls, hyaline, 6.2–359.2 µm long, 2.3–4.9 µm wide, with a septum 10.3–16.1 µm below apophyses, occasionally with a swelling below a septum. Sporangia globose to pyriform, multi-spored, subhyaline, smooth, deliquescent-walled, colorless when juvenile, dusky brown when old, 8.5–31.6 µm long, 8.8–26.1 µm wide. Columellae globose, subglobose, conical, smooth, subhyaline or hyaline, 2.1–10.2 µm long, 5.6–14.7 µm wide. Apophyses obvious, funnel-shaped, subhyaline or hyaline, slightly pigmented, 2.8–6.8 μm high, 1.7–3.4 µm wide at the base, and 5.0–14.8 µm wide at the top. Projections mostly cylindrical, always present, rarely absent, subhyaline or hyaline, 1.0–2.8 µm long, 0.8–2.2 µm wide. Collars present or absent; if present, 1.3–4.8 µm long. Sporangiospores cylindrical, oval, slightly concave in the center, smooth, hyaline, 2.2–6.2 µm long, 1.7–3.6 µm wide. Chlamydospores absent. Zygospores not found.

Culture characteristics.

Colonies on PDA at 25 ° C for 7 days, reaching 60 mm in diameter, indicating an average growth rate of approximately 7.8–8.6 mm / d, hyaline initially, light brownish when old, irregularly concentrically zonate with ring, sporadically petalous at margin, irregular in reverse.

Maximum growth temperature.

29 ° C.

Additional specimen examined.

China • Yunnan Province, Longling County, Mengnuo Town (24°31'25"N, 99°00'42"E, altitude 1319.65 m), from a soil sample, 8 July 2024, Z. Y. Ding and X. Y. Liu, living culture XG 10012-8 .

Notes.

Based on the SSU-ITS-LSU- Act - TEF 1 α sequences, two strains of the A. simplex sp. nov. formed into an independent branch with full support (MLBV = 100, BIPP = 1.00; Fig. 1 ), closely related to A. panacisoli ( Zhang et al. 2018) . These two species evidently differed in the morphology of stolons, sporangiophores, columellae, and sporangiospores. The maximum width of the stolons of A. simplex was narrower than those of A. panacisoli (10.0 µm vs. 10.5 µm). The maximum sporangiophore length of A. simplex was wider than that of A. panacisoli (4.9 µm vs. 2.8 µm). The columellae of A. simplex presented conical shapes, while A. panacisoli were absent. The sporangiospores of A. simplex possessed two shapes: cylindrical and oval, while those of A. panacisoli were mainly short and cylindrical. The zygospores of A. simplex were absent, while those of A. panacisoli were evident. Physiologically, the maximum growth temperature of A. simplex was lower than that of A. panacisoli (29 ° C vs. 32 ° C) ( Zhang et al. 2018).

Figures

Figure 1. The maximum likelihood phylogenetic tree of Absidia based on concatenated sequences of ITS rDNA, LSU rDNA, TEF 1 α, Act, and SSU rDNA, with Cunninghamella blakesleeana and C. elegans as outgroups. Maximum likelihood bootstrap values (MLBV ≥ 70 %) and Bayesian inference posterior probabilities (BIPP ≥ 0.9) are shown at the nodes, separated by slashes “ / ”. Ex-type or ex-holotype strains are indicated in bold black with an asterisk “ * ”. Strains obtained in this study are highlighted in red. Some branches are shortened for overall tree layout, indicated by “ // ”, with “ × ” denoting the fold of shortening. The scale bar at the bottom left represents substitutions per site.

Figure 3. Morphologies of Absidia simplex ex-holotype CGMCC 3.28541. a, b. Colonies on PDA; a. Obverse; b. Reverse; c, d. Sporangium; e – h. Columellae, collars, projections, and septa; i. Monopodial sporangiophores; j. Branched sporangiophores; k. Rhizoids; l. Sporangiospores. Scale bars: 10 μm (c – l).