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

Fig. 5

Type.

America • from a soil sample, X. Y. Liu, holotype HMAS 353366 , ex-holotype living culture CGMCC 3.28542 (= XY 00690) .

Etymology.

The sphaerica (Lat.) refers to the spherical columellae.

Description.

Hyphae branched, hyaline at first, light brown when mature, aseptate when young, septate with age. Stolons branched, smooth, hyaline, septate, 6.3–10.1 µm in diameter. Rhizoids root-like, hyaline, rarely branched, occasionally with a swelling. Sporangiophores beginning with stolons, erect or slightly bent, single or 2–5 in whorls, unbranched or branched 1–2 times, hyaline, 11.7–171.0 µm long, 2.7–4.6 µm wide, with one to two septa 6.4–18.2 µm below apophyses. Sporangia spherical, pear-shaped, multi-spored, smooth, deliquescent-walled, colorless in youth, pigmented when old, 6.9–37.0 µm long, 6.6–30.9 µm wide. Columellae globose, subglobose, smooth, hyaline, 1.2–20.2 µm long, 3.5–20.9 µm wide. Apophyses funnel-shaped, hyaline, slightly pigmented, 5.4–14.3 μm high, 1.3–5.0 µm wide at the base, and 3.3–16.3 µm wide at the top. Projections evident, strip-shaped, papillary, or pacifier-like, 2.0–7.3 µm long, 1.5–3.6 µm wide. Collars present or absent; if present, 1.4–6.4 µm long. Sporangiospores mostly cylindrical, occasionally globose, smooth, hyaline, 2.7–3.6 µm long, 1.2–2.2 µm wide. Chlamydospores absent. Zygospores not found.

Culture characteristics.

Colonies on PDA at 25 ° C for 7 days, reaching 79 mm in diameter, exhibiting an average growth rate of approximately 10.2–11.3 mm / d, hyaline at first, light brown when mature, regular in reverse.

Maximum growth temperature.

33 ° C.

Additional specimen examined.

The United States of America • from a soil sample, latitude, longitude, and altitude unknown, X. Y. Liu, living culture XY 00690-1 .

Notes.

Based on the SSU-ITS-LSU- Act - TEF 1 α phylogenetic tree, two strains of the A. sphaerica sp. nov. formed a fully supported independent lineage (MLBV = 100, BIPP = 1.00; Fig. 1 ), closely related to A. medulla ( Zong et al. 2021 a) . Although similar, they were different in terms of morphological features such as rhizoids, stolons, sporangiophores, sporangia, columellae, apophyses, projections, and sporangiospores. A. sphaerica in rhizoids had no spine-like structures, while A. medulla presented them. The maximum width of the stolons of A. sphaerica was wider than those of A. medulla (10.1 µm vs. 6.5 µm). The maximum sporangiophore length of the former was much shorter than that of the latter (171.0 µm vs. 220 µm). In addition, A. sphaerica was smaller than A. medulla in sporangia (6.9–37.0 × 6.6–30.9 μm vs. 12–41 × 11.5–32.5 μm). The columellae in A. sphaerica were slightly shorter than in A. medulla (1.2–20.2 µm vs. 8.5–20.5 µm), accompanied by a longer projection at its top (2.0–7.3 µm vs. 1–4.5 µm). The apophyses of A. sphaerica were not only shorter in height than A. medulla (1.2–7.5 µm vs. 3.0–8.5 µm) but also narrower in top width (3.3–16.31 µm vs. 7.5–17.5 µm). In addition, the septum was closer to apophyses in A. sphaerica than in A. medulla (6.4–18.2 µm vs. 12.5–27.5 µm). The sporangiospores in A. sphaerica are smaller than in A. medulla (2.7–3.6 µm × 1.2–2.2 µm vs. 3.0–4.5 µm × 2.0–3.5 µm). Physiologically, the maximum growth temperature of A. sphaerica was lower than that of A. medulla (33 ° C vs. 32 ° C) ( Zong et al. 2021 a).

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 5. Morphologies of Absidia sphaerica ex-holotype CGMCC 3.28542. a, b. Colonies on PDA; a. obverse; b. Reverse; c. Sporangium; d. Branched sporangiophores; e. Whorled sporangium; f. Monopodial sporangiophores; g – h. Columellae, collars, projections, and septa; j. Rhizoids with a swelling; k. Zygospores; l. Sporangiospores. Scale bars: 10 μm (c – l).