Three New Aquatic Fungi Species Discovered in Philippine Waters

Deep in the streams, lakes and intertidal zones of the Philippine island of Panay, a quiet but significant discovery has been made. Researchers surveying fungi that live on submerged decaying wood have identified three species entirely new to science, all belonging to the poorly studied genus Distoseptispora, and have reported the first Philippine occurrence of a fourth species previously known only from China. The findings, published in the journal MycoKeys, mark the first documented record of this genus anywhere in Philippine aquatic habitats and shine a spotlight on the Visayas region as an overlooked centre of fungal biodiversity.

Aquatic fungi are far more than obscure biological curiosities. They colonise an extraordinary range of environments, from rivers, streams and lakes to deep-sea sediments, hydrothermal vents, polar waters, aquifers and even nuclear reactors. Across all these settings they perform a fundamental ecological service: breaking down organic matter and anchoring aquatic food webs. The lignicolous aquatic fungi, those that inhabit submerged wood, are particularly important decomposers. By degrading lignocellulose, the tough structural material of plants, they soften sunken timber and release nutrients back into the water, driving carbon and nutrient cycling in both freshwater and marine systems.

Despite their ecological importance, comprehensive data on aquatic fungal diversity in the Philippines remain scarce. Current estimates suggest roughly 2,319 marine fungal species and about 3,870 freshwater species worldwide, and while recent years have seen a surge of novel fungal discoveries from China and Thailand, the Philippine archipelago has remained largely unmapped territory for these organisms. The new study, led by researchers working with the University of the Philippines Visayas, begins to close that gap.

The genus at the centre of the discovery belongs to the order Distoseptisporales, a species-rich but taxonomically isolated group within the class Sordariomycetes. Members of Distoseptispora are saprobes, organisms that feed on dead organic matter, and are most commonly associated with woody substrates in freshwater and terrestrial habitats, where they contribute to lignocellulose degradation. The genus is identified largely by its asexual reproductive structures: distinctive spore-producing stalks and elongated, often beautifully sculpted conidia, the asexual spores, characterised by a type of internal cross-wall called a distoseptum, along with characteristic size, shape and pigmentation. Most known species have been reported from Asia, particularly China and Thailand, making the Philippine finds a notable extension of the group’s known range.

The fieldwork behind the discovery involved collecting submerged decaying wood from aquatic habitats on Panay Island and Nogas Island. Samples were incubated in moist chambers for two weeks to encourage sporulation, after which the researchers examined fungal fruiting bodies under dissecting and compound microscopes, photographing and measuring structures such as conidiophores and conidia. Pure cultures were established through single-spore isolation on potato dextrose agar, and voucher specimens were deposited in the University of the Philippines Visayas Mycological Herbarium, with living cultures preserved in the university’s microbial culture collection.

To confirm that the isolates truly represented new species, the team turned to DNA. Genomic material extracted from fresh mycelia was amplified at four genetic loci, the internal transcribed spacer region, the large subunit of ribosomal RNA, the second largest subunit of RNA polymerase II and translation elongation factor 1-alpha, and sequenced at the Philippine Genome Center Visayas. The resulting sequences, along with reference data from 164 taxa, were aligned and analysed using both Maximum Likelihood and Bayesian Inference methods. The combined dataset spanned 3,861 aligned characters, providing a robust evolutionary framework for judging where each new isolate belonged on the fungal tree of life.

The phylogenetic results, combined with detailed morphology, confirmed three novel species. Distoseptispora antiqueana, collected from submerged wood in the intertidal zone of Nogas Island in Antique Province, is especially significant: it represents only the second confirmed record of the genus from a marine habitat, after D. mangrovei was described from China. The species produces conidia ranging from 139 to 268 micrometres in length with up to 39 distosepta, and differs from its closest relatives by clear sequence divergence in the protein-coding genes, including 7.56 per cent divergence in TEF1-alpha from its nearest matched species. The other two species, D. iloiloensis from Tinagong Dagat Lake and D. panayensis from Busay-lapad Falls, both in Iloilo Province, came from freshwater streams and were distinguished from related Thai and Chinese species through combinations of conidial dimensions, conidiophore structure and consistent nucleotide differences across loci.

Alongside the new species, the study reported a new geographic record for D. septata, a species originally described from a freshwater stream in China. The Philippine strain clustered with the Chinese holotype strain with maximal statistical support, 100 per cent Maximum Likelihood bootstrap support and a Bayesian posterior probability of 1.00, and showed no sequence differences in the ITS and RPB2 loci and only minor variation in LSU and TEF1-alpha. Although the Philippine collection bore longer conidia and shorter conidiophores than the type material, the researchers concluded that such variation falls within the documented phenotypic range of conspecific isolates, given that species delimitation in this genus rests on the integration of molecular and morphological evidence.

The phylogenetic analyses also prompted taxonomic housekeeping elsewhere in the genus. Two previously described species were found to be synonyms of older names: D. thailandica was merged under D. phangngaensis, and D. mengsongensis was merged under D. fasciculata, in each case because the sequences differed only minimally and the trees placed the ex-type strains together with strong support. In both instances the researchers attributed the observed differences in conidial size, septation and pigmentation to ecological plasticity, the tendency of fungal morphology to shift with substrate and habitat conditions, rather than to genuine species-level distinction. The revisions follow the principle of priority, retaining the earlier-published names.

The study’s authors note that while their multigene approach resolves species-level relationships effectively, deeper evolutionary branches within Distoseptispora remain weakly supported, suggesting that broader taxon sampling and additional protein-coding loci or whole-genome data will be needed to fully reconstruct the genus’s history. One limitation was the failure to obtain a usable LSU sequence for D. antiqueana despite repeated attempts, leaving that species defined by three loci rather than four. Even so, the message of the work is clear: tropical aquatic habitats in Southeast Asia still conceal a wealth of undocumented fungal diversity, and the Philippines, with its intertidal mangroves, lakes and mountain streams, is emerging as a frontier worth exploring in earnest.

Subject of Research: Discovery and phylogenetic characterisation of novel aquatic Distoseptispora fungal species in the Philippines

Article Title: Three novel aquatic species of Distoseptispora ( Distoseptisporaceae , Distoseptisporales ) from the Philippines, with a new geographic record for D. septata

Article References: Bagacay, J. F. E., Candole, G. M., Velo, J. C., Sara, F. R., Siccio, M. A., Opiña, L. A., Jones, E. B. G., & Calabon, M. S. (2026). Three novel aquatic species of Distoseptispora (Distoseptisporaceae, Distoseptisporales) from the Philippines, with a new geographic record for D. septata. MycoKeys, 137, 103-137. https://doi.org/10.3897/mycokeys.137.198252

Image Credits: AI Generated

DOI: 10.3897/mycokeys.137.198252

Keywords: Distoseptispora, aquatic fungi, Philippines, mycology, taxonomy, phylogenetics, freshwater fungi, biodiversity, saprobes, Southeast Asia, new species, lignicolous fungi