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

Fig. 2

Type.

China • Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Menghai County G 219 (Xijing Line) (22°11'02"N, 100°17'22"E, altitude 1492.96 m), from soil, 7 July 2024, Z. Y. Ding and X. Y. Liu, holotype HMAS 353363 , ex-holotype living culture CGMCC 3.28540 (= XG 09770-7) .

Etymology.

The epithet arrhiza (Lat.) refers to producing few rhizoids in this species.

Description.

Hyphae branched, hyaline at first, gradually becoming brown when mature, aseptate when young, septate with age. Stolons branched, smooth, hyaline, brownish, septate, 3.7–9.7 µm in diameter. Rhizoids root-like, hyaline, poorly developed, simply branched. Sporangiophores arising from stolons, erect or slightly bent, single or 2–3 in whorls, unbranched, hyaline, 10.6–150.5 µm long, 2.4–5.3 µm wide, with a septum 14.4–18.7 µm below apophyses. Sporangia globose, multi-spored, smooth, deliquescent-walled, colorless when young, brownish when old, 10.5–38.8 µm long, 10.6–35.8 µm wide. Columellae subglobose to globose, smooth, hyaline, 5.0–11.5 µm long, 7.5–17.0 µm wide. Apophyses distinct, funnel-shaped, hyaline, slightly pigmented, 4.0–8.8 μm high, 2.1–4.5 µm wide at the base, and 5.0–17.6 µm wide at the top. Projections mostly pacifier-like, 0.7–6.5 µm long, 1.5–3.6 µm wide. Collars present or absent; if present, 1.8–4.9 µm long. Sporangiospores cylindrical, slightly concave in the center, smooth, hyaline, 2.8–4.5 µm long, 1.4–2.7 µm wide. Chlamydospores absent. Zygospores not found.

Culture characteristics.

Colonies on PDA in darkness at 25 ° C for 7 days, growing slowly, reaching 79 mm in diameter, indicating an average growth rate of approximately 10.3–11.2 mm / d, hyaline at first, gradually becoming brown, irregular concentric ring zonate, petaloid, irregular at reverse.

Maximum growth temperature.

33 ° C.

Additional specimen examined.

China • Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Menghai County G 219 (Xijing Line) (22°11'02"N, 100°17'22"E, altitude 1492.96 m), from a soil sample, 7 July 2024, Z. Y. Ding and X. Y. Liu, living culture XG 09770-6 .

Notes.

According to the SSU-ITS-LSU- Act - TEF 1 α sequences, two strains of the Absidia arrhiza sp. nov. were formed into an independent branch with full support (MLBV = 100, BIPP = 1.00; Fig. 1 ), closely related to A. chinensis ( Zhao et al. 2023) . These two species were obviously different in the morphology of sporangiophores, sporangia, apophyses, and sporangiospores. The maximum length of the sporangiophores of A. arrhiza was shorter than those of A. chinensis (150.5 µm vs. 220.0 µm). A. arrhiza mainly owned the shape of globose sporangia, while A. chinensis had two shapes, including globose and pyriform. The apophyses of A. arrhiza were higher than those of A. chinensis (4.0–8.8 μm vs. 3.5–7.0 µm). The sporangiospores of A. arrhiza were mainly cylindrical, while those of A. chinensis were mainly cylindrical to oval. Z ygospores were absent in A. arrhiza , while present in A. chinensis . Physiologically, the maximum growth temperature of A. arrhiza was higher than that of A. chinensis (33 ° C vs. 30 ° C) ( Zhao et al. 2023).

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 2. Morphologies of Absidia arrhiza ex-holotype CGMCC 3.28540. a, b. Colonies on PDA; a. Obverse; b. Reverse; c, d. Sporangia; e – h. Columellae, collars, projections, and septa; i. Rhizoids; j. Sporangiospores. Scale bars: 10 μm (c – j).