A microscopic fungus growing on submerged, decaying wood in a freshwater habitat in Guizhou, China, has been recognized as a new genus and species, Dentisympodium fusiforme. The taxonomic discovery, described in MycoKeys, places the organism in Pleurotheciaceae, a family containing predominantly saprobic fungi that inhabit freshwater and terrestrial environments. The identification combined detailed observations of its asexual structures with a four-locus phylogenetic analysis, providing molecular and morphological evidence for treating Dentisympodium as a genus distinct from its closest sampled relative.
The type specimens were collected on 12 October 2025 from decaying wood at Changpo Ling National Forest Park in Baiyun District, Guiyang City. Fresh material was transported to the laboratory in labeled plastic bags and maintained in moistened tissue boxes at room temperature for one to two weeks. Researchers examined it with a stereomicroscope and compound microscope, recording and measuring the conidiophores, conidiogenous cells and conidia. They then isolated single germinating conidia on potato dextrose agar, where the resulting colonies were cultured for 36 days. Dried specimens were deposited in the herbarium of the Guizhou Academy of Agricultural Sciences, while living cultures were placed in the Guizhou Culture Collection.
Under the microscope, the collected fungus initially resembled Pseudodactylaria: both possess erect, unbranched, hyaline conidiophores and terminal conidiogenous cells that carry denticles and produce slender, septate conidia. The new taxon nevertheless differed in two conspicuous characters. Its conidiophores are irregularly subcylindrical and flexuous, and its conidia are predominantly three-septate, whereas Pseudodactylaria has strictly cylindrical conidiophores and conidia with zero or one septum. Molecular classification also separated the organisms: Dentisympodium was recovered within Pleurotheciaceae, in the orders Pleurotheciales and subclass Savoryellomycetidae, while Pseudodactylaria belongs to Pseudodactylariaceae in Pseudodactylariales and Sordariomycetidae.
To test the placement of the new isolates, researchers sequenced four fungal DNA regions: the internal transcribed spacer region, ITS; the large-subunit ribosomal RNA gene, LSU; the small-subunit ribosomal RNA gene, SSU; and part of the RNA polymerase beta-two gene, rpb2. Following sequence assembly and alignment, these loci were concatenated into a 3,503-character dataset representing 54 taxa. Maximum-likelihood and Bayesian inference analyses produced congruent tree topologies. Both analyses placed the two new isolates in a distinct, well-supported lineage within Pleurotheciaceae, with 100% maximum-likelihood bootstrap support and a Bayesian posterior probability of 1.00 for the relevant node.
Within Pleurotheciaceae, the Dentisympodium lineage appeared as the sister group of Phragmocephala stemphylioides, represented in the analysis by strain KAS 4277. The genetic separation was also visible in pairwise comparisons. Between Dentisympodium fusiforme and P. stemphylioides, the analysis recorded 56 differences across 536 aligned ITS base pairs, corresponding to 10.5% and including 20 gaps, and 17 differences across 842 LSU base pairs, or 2.0% when gaps were excluded. Their conidial structures remain clearly different: Dentisympodium has hyaline conidiophores, irregularly subcylindrical conidiogenous cells with aggregated denticles, and cylindrical, fusiform to obclavate, hyaline conidia, while P. stemphylioides has pale brown to brown conidiophores and obovoid, dematiaceous conidia.
The proposed genus name reflects two structural features described in the formal taxonomic treatment. “Denti” refers to the cylindrical denticles on the conidiogenous cells, while “sympodium” refers to the sympodial proliferation of those cells. The conidiogenous cells are holoblastic, polyblastic, integrated, terminal and sympodial, with an irregularly subcylindrical, flexuous form. Their apical region develops into a rachis bearing numerous aggregated cylindrical denticles. This combination of denticulate cells and sympodial proliferation, together with the shape and septation of the conidia, provides the basis for separating Dentisympodium from other genera in the family.
Dentisympodium fusiforme forms superficial, effuse and gregarious white colonies on its decaying-wood substrate. Its mycelium consists of branched, septate, hyaline hyphae that are partly immersed and partly superficial. The conidiophores measure 17–24 by 4–5 micrometres, with a mean of 19 by 4.5 micrometres based on 20 measurements. They are macronematous, mononematous, solitary, erect, unbranched, subcylindrical, flexuous, hyaline and zero- or one-septate. The conidiogenous cells measure 8.5–11 by 3.5–4.5 micrometres, with a mean of 10 by 4 micrometres from 20 measurements.
The conidia are solitary and acropleurogenous, measuring 19–34 micrometres long and 3.5–5 micrometres wide. The reported mean is 30 by 5 micrometres, calculated from 35 conidia. Most are three-septate, although the observed range extends from zero to three septa. They are cylindrical, fusiform to obclavate and subobtuse at the apex, with smooth, hyaline walls and prominent guttules. In culture, conidia germinated on potato dextrose agar within 11 hours and produced germ tubes from the conidial body. After 36 days at room temperature, approximately 25 degrees Celsius, the irregular colonies reached 31 centimetres in diameter, with flat to slightly raised surfaces and entire margins.
The culture surface became light brown to dark brown, with the point of attachment dark brown to nearly black and pigmentation radiating outward. The reverse ranged from pale yellow to grayish yellow, had a slightly darker center with olivaceous to gray-green tinges, and showed a lighter pale-yellow to whitish margin. The fungus is saprobic on submerged decaying wood in freshwater habitats, but its sexual morph remains undetermined. The published description therefore documents the asexual, hyphomycetous morph, and the taxonomic conclusion applies to the organism and lineage represented by the new specimens and cultures rather than to an observed sexual stage.
The discovery expands the recorded diversity of lignicolous freshwater fungi in Guizhou and refines the taxonomic framework of Pleurotheciaceae. The family is morphologically diverse: its asexual forms include acrodictys-like, helicoön-like, monodictys-like and dactylaria-like structures, and its sexual morph is characterized by dark, papillate, perithecial, astromatic ascomata, unitunicate asci with a non-amyloid apical annulus, and septate hyaline ascospores. At the time of the study, Pleurotheciaceae contained 17 accepted genera, although molecular data remained unavailable for numerous taxa and several genera were represented by only a limited number of collections.
The authors also note that molecular evidence has shown the genus Phragmocephala to be polyphyletic, with its species distributed among three families: Melanommataceae in Pleosporales, Microthyriaceae in Microthyriales, and Pleurotheciaceae in Pleurotheciales. The placement of Dentisympodium as a distinct, strongly supported lineage illustrates why DNA-based analysis can resolve relationships that resemble one another morphologically. The study is a single-collection and culture-based taxonomic description from one freshwater site, and its conclusions concern the sampled lineage rather than the known distribution or ecological behavior of the entire genus. Nevertheless, the combined evidence supports Dentisympodium as a new genus with D. fusiforme as its type species, adding a genetically and morphologically distinct member to the diversity of wood-inhabiting freshwater fungi in China.
Subject of Research: Morphological and four-locus phylogenetic characterization of a novel freshwater fungus from Guizhou, China
Article Title: Morpho-phylogenetic analyses reveal Dentisympodium fusiforme gen. et sp. nov. in Pleurotheciaceae ( Pleurotheciales , Savoryellomycetidae ) from China
Article References: Zhang, W., Feng, Q., Xie, W., Song, X., Zhou, X., Lu, J., Yang, Y., & Li, Z. (2026). Morpho-phylogenetic analyses reveal Dentisympodium fusiforme gen. et sp. nov. in Pleurotheciaceae (Pleurotheciales, Savoryellomycetidae) from China. MycoKeys, 136, 99-118. https://doi.org/10.3897/mycokeys.136.195305
Image Credits: AI Generated
DOI: 10.3897/mycokeys.136.195305
Keywords: new fungal genus, new fungal species, freshwater fungi, Pleurotheciaceae, Dentisympodium fusiforme, phylogenetics, submerged wood, Guizhou, fungal taxonomy, saprobic fungi, Morpho-phylogenetic, analyses
News Source: Roger Howard. (October 20, 2026). Four-Gene Analysis Reveals New Freshwater Fungus Genus in China. Scienmag.
