Unveiling Species Diversity Within Early-Diverging Fungi from China XIII: Four New Species of Absidia (Cunninghamellaceae, Mucoromycota)

TL;DR

Four new species of fungi in the genus Absidia were discovered in Chinese soil samples, increasing the known species count to 66.

Contribution

The paper introduces four new Absidia species identified through morphological and molecular analyses in China.

Findings

Four new Absidia species (A. brunneola, A. digitata, A. exilis, A. tumida) were identified in China.

Molecular and morphological data confirmed the novelty of these species.

The total number of recognized Absidia species now reaches 66.

Abstract

The genus Absidia is predominantly distributed in soil habitats. During the fungal investigation of soil collected from China (Guangxi, Yunnan, and Chongqing), four novel species of Absidia were identified, namely Absidia brunneola sp. nov., A. digitata sp. nov., A. exilis sp. nov., and A. tumida sp. nov. This identification was based on morphological characteristics and molecular analyses of the internal transcribed spacer (ITS), small subunit (SSU) and large subunit of ribosomal RNA gene (LSU rDNA), actin gene (ACT), and translation elongation factor 1-alpha gene (TEF1α). Absidia brunneola sp. nov. is sister to A. jiangxiensis, which is characterized by the production of light brown sporangia. Absidia digitata sp. nov. and A. tumida sp. nov. are sister to each other with the former species developing digitiform rhizoids and the latter swollen in sporangiophores. Absidia exilis sp. nov. is closely related to A. oblongispora, exhibiting poorly developed sporangiophores. To date, the total number of recognized species within the genus Absidia has increased to 66, including the four new ones herein.

Figures

Full text

1. Introduction

The genus Absidia was first formally proposed by van Tieghem in 1876 and typified by A. reflexa [1], and it currently belongs to Cunninghamellaceae, Mucorales, Mucoromycetes, and Mucoromycota. It is widely distributed and has been reported in all continents except Antarctica [2,3,4]. Over the past decade, at least 20 species have been successively reported in countries around the world, mainly including Brazil, China, South Korea, and Thailand [5,6,7,8,9,10,11,12,13,14,15,16]. In China, this genus was mainly found in southern hot areas, such as Yunnan, Hainan, and Sichuan provinces; it can also be sporadically found in certain regions with low temperatures, including northeast and northwest provinces [7]. As a saprophytic fungal group, it is primarily isolated from soil samples, and it is also distributed in herbivorous animal feces, decaying materials, and air [5,9,14,17,18,19]. Being a fungal genus of significant research value, Absidia holds important applications in industrial and medicinal fields. It can produce various secondary metabolites including α-galactosidase, steroids, and fatty acids [5,20,21,22,23,24], and some species are capable of participating in the biotransformation of natural products such as flavones, flavanones, and cresol red [23,25].

The taxonomic status of the genus Absidia has long been controversial. Initially assigned to the family Absidiaceae [26] upon its proposal, it was subsequently classified under Mucoraceae [27]. At present, it is placed within Cunninghamellaceae [28]. Drawing upon phylogenetic and morphological evidence, recent studies have demonstrated that Absidia sensu lato encompasses three genera, namely Absidia sensu stricto, Lentamyces, and Lichtheimia [29,30,31]. Species of the genus Absidia exhibit distinct morphological characteristics, which are mainly manifested as follows: sporangiophores are scattered along the stolons, showing an asymmetrical distribution relative to rhizoids, and they can be solitary, paired, clustered, or verticillate; rhizoids occur on stolons; sporangia mostly pyriform to subglobose with deliquescent walls and distinct apophyses; columellae usually bear apical protrusions. Studies conducted by Ding et al. [32] and Ji et al. [33] indicated that the number of recognized species within this genus has reached 62 to date.

Based on molecular phylogenetic and morphological characteristics, this paper presents a thorough characterization of four new Absidia species isolated and verified from soil specimens sampled in the Guangxi Zhuang Autonomous Region, Yunnan Province, and Chongqing Municipality, China. This constitutes the thirteenth report in a serial study focusing on the diversity of early-diverging fungi in China [32,33,34,35,36,37,38].

2. Materials and Methods

2.1. Sample Collection and Strain Isolation

In 2025, we collected soil samples from the Guangxi Zhuang Autonomous Region, Yunnan Province, and Chongqing Municipality of China, following the methodologies outlined by Liu et al. [39] and Zou et al. [40]. Roughly 50 g of each sample was placed into a sterile sealed bag with labels indicating the sample number, vegetation type, collection date, longitude, latitude, and altitude. After collection, all samples were transported back to the laboratory and stored at 4 °C (Cat. No.: LSC-650E, Zhejiang Xingxing Cold Chain Integration Co., Ltd., Taizhou, China). Fungal isolation and purification were performed using a combination of the single-spore isolation method and the serial dilution plate method [40,41] with a detailed procedures as follows: Approximately 1 g of soil sample was weighed and transferred to a test tube containing 9 mL of sterile water. After shaking thoroughly, a 10^−1^ soil suspension was prepared. An aliquot of 1 mL of the initial suspension was transferred to another test tube with 9 mL of sterile water, and then it was fully mixed to obtain a 10^−2^ suspension. This serial dilution step was repeated sequentially to prepare 10^−3^ and 10^−4^ suspensions. An aliquot of 200 μL from each of the 10^−3^ and 10^−4^ dilutions was pipetted onto the surface of Rose Bengal Chloramphenicol Agar (RBC) (Cat. No.: HB0237-3, Qingdao Hope Bio-Technology Co., Ltd., Qingdao, China) plates [42] supplemented with 0.03% streptomycin sulfate. The RBC medium composition was as follows: peptone 5.00 g/L, glucose 10.00 g/L, MgSO_4_·7H_2_O 0.50 g/L, KH_2_PO_4_ 1.00 g/L, rose bengal 0.05 g/L, chloramphenicol 0.10 g/L, and agar 15.00 g/L. Each inoculated plate was then uniformly spread using a sterile glass spreader. The inoculated plates were incubated in a 25 °C incubator in the dark for 3 d. Subsequently, under a stereomicroscope (Olympus SZX10, Tokyo, Japan), sporangia of the target strains were picked using a sterile inoculating loop and transferred onto Potato Dextrose Agar (PDA) (Cat. No.: HB0233, Qingdao Hope Bio-Technology Co., Ltd., Qingdao, China) plates with the following medium composition: 6.00 g/L potato infusion powder, 20.00 g/L dextrose, and 20.00 g/L agar, which was followed by incubation in the dark at 25 °C Incubator (Cat. No.: 1010159, Ningbo Jiangnan Instrument Factory, Taizhou, China). After purification, the strains were preserved with 10% glycerol at 4 °C refrigerator (Cat. No.: LSC-650E, Zhejiang Xingxing Cold Chain Integration Co., Ltd., Taizhou, China).

The dried type specimens were preserved in the Herbarium Mycologicum Academiae Sinicae (HMAS; Beijing, China). The ex-type strains were deposited at the China General Microbiological Culture Collection Center (CGMCC; Beijing, China). Replicated experiments were performed at Shandong Normal University (XG; Jinan, China). Taxonomic details pertaining to the novel taxa have been submitted to the Fungal Names database (https://nmdc.cn/fungalnames/, accessed on 15 January 2026).

2.2. Morphological Observation

Macroscopic morphological traits were recorded via photography using a high-definition color digital camera (DP80, Olympus, Tokyo, Japan). Simultaneously, the microscopic morphological features of the fungal isolates were examined with a stereomicroscope (Olympus SZX10; Olympus, Tokyo, Japan) and a light microscope (BX53; Olympus, Tokyo, Japan). Subsequently, Digimizer software v 6.0.0 (https://www.digimizer.com/, accessed on 2 November 2025) was used for microstructure measurements with each characteristic (sporangiophores, columellae, sporangiospores, and so on) measured at least 50 times. Finally, Adobe Photoshop CC 2019 (https://www.adobe.com/products/photoshop.html, accessed on 8 November 2025) was employed for image typesetting of the captured microstructures.

2.3. DNA Extraction, PCR Amplification, and Sequencing

We inoculated the strain onto PDA medium and incubated in a 25 °C incubator under dark conditions for 3–5 d; then, fungal genomic DNA was extracted using either the Beaver Beads Plant DNA Kit (BEAVER Biomedical Engineering Co., Ltd., Cat. No.: 70409-20, Suzhou, China) or the CTAB method [43,44]. Polymerase chain reaction (PCR) was employed to amplify the ITS, LSU rDNA, TEF-1α, ACT, and SSU gene regions with the primer pairs ITS4/ITS5 [45], LR0R/LR5 [46], EF1-983F/TEF1LLErev [47,48], ACT-1/ACT-4R [49], and NS1/NS4 [45] utilized for each respective region (Table 1). The PCR amplification was carried out in a total volume of 25 μL, which contained 12.5 μL of 2× Hieff Canace^®^ Plus PCR Master Mix (Yeasen Biotechnology, Shanghai, China; Cat. No.: 10154ES03), 9.5 μL of double-distilled water (ddH_2_O), 1 μL each of the forward and reverse primers (10 μM, TsingKe Biotechnology Co., Ltd., Beijing, China), and 1 μL of fungal DNA template. Upon completion of amplification, the resulting products were separated via 1% agarose gel electrophoresis and visualized under ultraviolet light [50]. Target bands were excised and purified using a Gel Extraction Kit (Cat. No.: AE0101-C; Shandong Sparkjade Biotechnology Co., Ltd., Jinan, China), and subsequent DNA sequencing was conducted by Sangon Biotech (Shanghai, China) Co., Ltd. Consensus sequences were assembled using Geneious Prime 2025.0.2 software (https://www.geneious.com, accessed on 14 July 2025). All sequences were deposited at the National Microbiology Data Center (https://nmdc.cn/, accessed on 6 December 2025) with the accession numbers provided in Table S1.

2.4. Phylogenetic Analyses

All sequences were retrieved from the National Center for Biotechnology Information (https://www.ncbi.nlm.nih.gov/, accessed on 9 October 2025) with reference to recently published articles on the genus Absidia [32,33], and detailed information of all sequences is provided in Table S1. Sequence alignment and concatenation were performed using Geneious Prime 2025.0.2 software. Based on the combined ITS-SSU-LSU-ACT-TEF1α sequence dataset, phylogenetic trees were constructed using two methods: maximum likelihood (ML) and Bayesian inference (BI). The ML analysis was conducted on the CIPRES Science Gateway (https://www.phylo.org/, accessed on 15 October 2025) using RAxML 8.2.4 software with 1000 bootstrap replicates [51]. For the Bayesian inference analysis, the GTR + I + G model was utilized with sampling conducted at intervals of 1000 generations. Eight cold Markov chains were operated concurrently for a total of 2,000,000 generations [51,52]. The generated phylogenetic tree was optimized through the iTOL web platform (https://itol.embl.de, 17 October 2025) and visually polished using Adobe Illustrator CC 2019 software (https://adobe.com/products/illustrator, 18 October 2025).

3. Results

3.1. Phylogeny

Phylogenetic analysis was performed based on a molecular dataset including 109 strains, comprising 66 species of the genus Absidia, as well as two taxa selected as outgroups (i.e., Cunninghamella blakesleeana and Cunninghamella elegans). The dataset consisted of a total of 5189 concatenated characters, covering five fragments ITS (positions 1–1236), SSU (1237–2344), LSU (2345–3413), ACT (3414–4335), and TEF1α (4336–5189). Among these characters, 2901 were constant characters, 563 were variable but parsimony-uninformative characters, and 1725 were parsimony-informative characters. The maximum likelihood (ML) tree and Bayesian inference (BI) tree exhibited topological congruence, so the ML tree was selected for comprehensive visualization (Figure 1). Eight Absidia strains obtained in the present study formed four well-defined clades, each receiving full statistical support in the phylogenetic tree.

3.2. Taxonomy

Absidia brunneola W.X. Liu, H. Zhao & X.Y. Liu, sp. nov., Figure 2.

Fungal Names: FN 573310.

Type: China, Guangxi Zhuang Autonomous Region, Fangchenggang City, Shangsi County, Shiwanda Mountain National Forest Park. (21°90′58″ N, 107°90′36″ E, altitude 277.0 m), from soil, 9 February 2025, W. X. Liu, holotype HMAS 354234, ex-holotype living culture CGMCC 3.29490 (=XG12984-12-1).

Etymology: The epithet brunneola (Lat.) refers to the light brown sporangia.

Description: Colonies on PDA at 25 °C for 4 d, reaching 73 mm in diameter, fast growing with a rate of 18.3 mm/d. Mycelium grows on the surface of the agar medium. Hyphae initially white, gradually turning brown with age, aseptate when young and septate at maturity, 3.9–19.0 μm wide. Stolons septate, branched, hyaline or slightly brownish, 3.3–10.2 μm wide. Rhizoids well developed, hyaline, root-like. Sporangiophores arising from stolons, erect or slightly bent, mostly unbranched or with simple branches, single or 2–5 in whorls, 19.6–281.0 μm long, 1.8–5.6 µm wide with a septum 12.4–23.4 μm below the apophysis. Sporangia globose or pyriform, light brown, smooth-walled, deliquescent, 12.9–49.6 μm long, 10.9–49.6 µm wide. Columellae globose or subglobose, hyaline or subhyaline, smooth walled, 7.6–25.3 μm long, 7.1–21.4 µm wide. Projections present or absent; if present, solitary and crystal-like. Apophyses present, funnel shaped, 6.1–23.1 μm high, 2.6–6.8 μm wide at the base, and 10.6–30.2 μm wide at the top. Collars present or absent. Sporangiospores ovoid, hyaline, smooth walled, 2.3–4.5 μm long and 1.9–2.5 μm wide. Chlamydospores absent. Zygospores unknown.

Additional strains examined. China, Guangxi Zhuang Autonomous Region, Fangchenggang City, Shangsi County, Shiwanda Mountain National Forest Park (21°90′58″ N, 107°90′36″ E, altitude 277.0 m), from soil, 9 February 2025, W. X. Liu, living culture XG12984-12-2.

Notes. On the phylogenetic tree constructed from the concatenated ITS–SSU–LSU–ACT–TEF1α sequences, strains CGMCC 3.29490 and XG12984-12-2 cluster together to form a single clade with a support value of MLBS/BIPP = 95/1.00 (Figure 1), sister to Absidia jiangxiensis [19]. Morphologically, the sporangiophores of these two strains exhibit simple branches with up to five in a whorls arrangement, and their sporangia are light brown. In contrast, the sporangiophores of A. jiangxiensis are unbranched with up to six in a whorls arrangement. Based on molecular phylogenetic analyses and morphological observations, these two strains are proposed as a novel species A. brunneola.

Absidia digitata W.X. Liu, H. Zhao & X.Y. Liu, sp. nov., Figure 3.

Fungal Names: FN 573311.

Type. China, Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Mengla Town, G213. (21°51′58″ N, 101°50′77″ E, altitude 878.19 m), from soil, 19 May 2025, W. X. Liu, holotype HMAS 354235, ex-holotype living culture CGMCC 3.29492 (=XG18784-2-1).

Etymology: The epithet digitata (Lat.) refers to the species producing digitiform rhizoids.

Description. Colonies on PDA at 25 °C for 4 d, reaching 56 mm in diameter, fast growing with a rate of 14 mm/d. Mycelium grows on the surface of the agar medium. Hyphae are initially white, gradually becoming grayish-brown with age, aseptate when young and septate when mature, 3.9–15.8 μm wide. Stolons septate, branched, hyaline or slightly brownish with a diameter of 2.9–12.7 μm. Rhizoids well developed, hyaline, and finger-shaped. Sporangiophores arising from stolons, erect or slightly bent, occasionally swollen, mostly unbranched or with simple branches, single or 2–3 in whorls, 23.9–165.1 μm long, 2.7–4.3 µm wide with a septum 11.5–19 μm below the apophysis. Sporangia pyriform, rarely globose, hyaline, smooth-walled, deliquescent walled, 19.1–33.5 μm long, 17.7–26.2 µm wide. Columella globose, hyaline, smooth walled, 6.6–17.8 μm long, 6.3–12.7 μm wide. Projections present, pacifier shaped. Apophysis distinct, funnel-shaped, hyaline and slightly light brown, 6.4–12.9 μm high, 2.7–5.2 μm wide at the base and 8.6–25 μm wide at the top. Collars present. Sporangiospores oval, smooth walled, hyaline, 2.4–4.9 μm long, 1.8–3.1 μm wide. Chlamydospores not found. Zygospores unknown.

Additional strains examined. China, Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Mengla Town, G213 (21°51′58″ N, 101°50′77″ E, altitude 878.19 m), from soil, 19 May 2025, W. X. Liu, living culture XG18784-2-2.

Notes. On the phylogenetic tree constructed from the concatenated ITS–SSU–LSU–ACT–TEF1α sequences, strains CGMCC 3.29492 and XG18784-2-2 cluster together to form a single clade with a support value of MLBS/BIPP = 88/1.00 (Figure 1), sister to Absidia tumida. Morphologically, the sporangiophores of these two strains were at most three in whorls, producing digitiform rhizoids. However, the sporangiophores of A. tumida were at most four in whorls, and rhizoids are root-like. Based on molecular phylogenetic analyses and morphological observations, these two strains are proposed as a novel species A. digitata.

Absidia exilis W.X. Liu, H. Zhao & X.Y. Liu, sp. nov., Figure 4.

Fungal Names: FN 573312.

Type. China, Chongqing, Xiushan Tujia and Miao Autonomous County, 242 National Road, near Bapai Village. (28°42′33″ N, 109°14′17″ E, altitude 421.65 m), from soil, 14 November 2025, W. X. Liu, holotype HMAS 354236, ex-holotype living culture CGMCC 3.29493 (=XG21013-11-1)

Etymology: The epithet exilis (Lat.) refers to the poorly developed sporangiophores.

Description. Colonies on PDA at 25 °C for 3 d, reaching 47 mm in diameter, fast growing with a rate of 15.7 mm/d. Mycelium grows on the surface of the agar medium. Hyphae initially white, gradually turning tawny-brown with age, aseptate when young and septate at maturity, 2.1–21.1 μm wide. Stolons septate, branched, hyaline or subhyaline, 2.5–9.3 μm wide. Rhizoids well developed, hyaline, root-like. Sporangiophores arising from stolons, erect or slightly bent, usually accompanied by a swelling, mostly unbranched or with simple branches, solitary or 2–4 in whorls, 42.0–197.9 μm long and 1.5–6.1 μm wide with a septum 7.1–18.5 μm below the apophysis. Sporangia globose, rarely pyriform, dark brown, sometimes laterally borne on stolons, smooth walled, deliquescent, 15.9–37.1 μm long, 10.5–33.1 μm wide. Columellae globose, subglobose, or rarely ellipsoidal, hyaline, smooth walled, 8.9–20.9 μm long, 7.9–17.6 μm wide. Projections present or absent, pacifier shaped. Apophyses present, funnel shaped, 7.4–17.9 μm high, 2.9–8.0 μm wide at the base and 13.5–29.5 μm wide at the top. Collars present or absent. Sporangiospores ovoid, hyaline, smooth walled, 2.8–4.8 μm long and 1.5–2.7 μm wide. Chlamydospores absent. Zygospores unknown.

Additional strains examined. China, Chongqing, Xiushan Tujia and Miao Autonomous County, 242 National Road, near Bapai Village (28°42′33″ N, 109°14′17″ E, altitude 421.65 m) from soil, 14 November 2025, W. X. Liu, living culture XG21013-11-2.

Notes. On the phylogenetic tree constructed from the concatenated ITS–SSU–LSU–ACT–TEF1α sequences, strains CGMCC 3.29493 and XG21013-11-2 cluster together to form a single clade with a support value of MLBS/BIPP = 73/1.00 (Figure 1), and they are closely related to Absidia oblongispora [19]. Morphologically, the sporangiophores of these two strains are commonly swollen and sometimes poorly developed, whereas those of A. oblongispora are well developed with no swelling observed. Based on molecular phylogenetic analyses and morphological observations, these two strains are proposed as a novel species A. exilis.

Absidia tumida W.X. Liu, H. Zhao & X.Y. Liu, sp. nov., Figure 5.

Fungal Names: FN 573313.

Type. China, Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Jinghong City, Mengyang Town, G8511 (22°21′66″ N, 100°88′59″ E, altitude 804.28 m), from soil, 25 July 2025, W. X. Liu, holotype HMAS 354237, ex-holotype living culture CGMCC 3.29491 (=XG18709-9-1)

Etymology: The epithet tumida (Lat.) refers to the swollen sporangiophores.

Description. Colonies on PDA at 25 °C for 4 d, reaching 60 mm in diameter, fast growing with a rate of 15 mm/d. Mycelium grows on the surface of the agar medium. Hyphae initially white, gradually turning dark brown with age, aseptate when young and septate at maturity, 3.5–14.2 μm wide. Stolons septate, branched, hyaline or subhyaline, 1.8–5.8 μm wide. Rhizoids well developed, hyaline, root-like. Sporangiophores arising from stolons, erect or slightly bent, sometimes swollen, mostly unbranched or with simple branches, solitary or 2–4 in whorls, 19.5–180.6 μm long, 1.3–5 µm wide with a septum 6.1–18.5 μm below the apophysis. Sporangia globose to pyriform, hyaline or brown, smooth walled, deliquescent, 12.1–37.4 μm long and 13.2–33.5 µm wide. Columellae globose or ovoid, hyaline, smooth walled, 4.2–17.7 μm long and 2.7–15 µm wide. Projections present or absent; if present, distinct and pacifier shaped. Apophyses distinct and conspicuous, funnel shaped, 3.4–15.7 μm high, 1.9–5.1 μm wide at the base, and 8.9–23.3 μm wide at the top. Collars present. Sporangiospores ovoid, hyaline, smooth walled, 2.6–4.7 μm long and 1.6–3.0 μm wide. Chlamydospores not observed. Zygospores unknown.

Additional strains examined. China, Yunnan Province, Xishuangbanna Dai Autonomous Prefecture, Jinghong City, Mengyang Town, G8511 (22°21′66″ N, 100°88′59″ E, altitude 804.28 m), from soil, 25 July 2025, W. X. Liu, living culture XG18709-9-2.

Notes. On the phylogenetic tree constructed from the concatenated ITS–SSU–LSU–ACT–TEF1α sequences, strains CGMCC 3.29491 and XG18709-2-2 cluster together to form a single clade with a support value of MLBS/BIPP = 99/1.00 (Figure 1), sister to A. digitata. In terms of morphology, sporangiophores of the two strains formed whorls with a maximum number of four per whorl, and the sporangia are brown. In contrast, the sporangiophores of A. digitata were at most three in whorls, and the sporangia are hyaline. Based on molecular phylogenetic analyses and morphological observations, these two strains are proposed as a novel species A. tumida.

4. Discussion

In the multi-locus phylogenetic tree, all these four new species each formed a well-supported clade (Figure 1). A comparative analysis of morphological characteristics between these four novel species and their closely related taxa was conducted (Table 2).

Absidia brunneola is sister to A. jiangxiensis [19]. Compared with A. jiangxiensis, A. brunneola exhibits a faster colony growth rate with a daily average of 18.3 mm. Its sporangia are colored light brown and the apophyses are hyaline, whereas the sporangia of A. jiangxiensis are hyaline and its apophyses are slightly greenish. Absidia digitata and A. tumida are sister groups. A comparative analysis revealed that A. digitata produces finger-shaped rhizoids with sporangiophores arranged in whorls of up to three at most, which are fewer in number. Projections are always present. In contrast, A. tumida has root-like rhizoids, the projections are present or absent, and its sporangia are brown. Absidia exilis is closely related to A. oblongispora [19]. In comparison, the sporangiophores of A. exilis are usually swollen and sometimes poorly developed, and its sporangia are dark brown and globose with a special lateral attachment pattern on the stolons. By contrast, the sporangiophores of A. oblongispora are well developed without swellings, and its sporangia are hyaline.

The genus Absidia is widely distributed across the globe with the highest prevalence in Europe and extreme rarity in Antarctica [2,3,4]. It is commonly found in tropical, subtropical, and temperate regions. In China, it is mainly distributed in areas such as Yunnan Province, the Xinjiang Uygur Autonomous Region, and Taiwan Region, and it has also been reported in other countries with similar climates, including Brazil and Thailand [8,9,10,13,14,18]. This genus inhabits diverse habitats such as soil, herbivore dung, decaying substrates, air, and insect remains [5,9,14,17,18,19], among which soil is its primary habitat. The four novel species described in this study were all isolated from soil, further confirming that Absidia is most extensively distributed in soil environments [53]. Species of Absidia can produce various secondary metabolites such as α-galactosidase, steroids, and fatty acids [22,23,24], and some species are capable of participating in biotransformation [23,25], laying an important foundation for their development and application. The four novel species reported in this study increase the total number of globally recognized Absidia species to 66, which enriches the species diversity of the genus and provides new and significant strain resources for exploring fungal secondary metabolites.