The research team, led by Ping He and Ke Zhang of Xizang Minzu University together with Jehangir Khan, Haoran Ouyang, Shujin Hu and colleagues at Sun Yat-sen University under the corresponding authorship of Datao Lin, collected giant African snails from Guangzhou in Guangdong Province, China, in November 2025. The sampling strategy was deliberately cross-sectional: rather than following individual animals over time, the researchers captured snails at three distinct developmental categories and compared the fungal communities in their gut contents. Genomic DNA was extracted directly from the gut material, and metagenomic sequencing was used to catalogue the fungi present. This approach, which sequences all the genetic material in a sample rather than targeting a single marker gene, allows researchers to identify fungal taxa with a resolution that older techniques could not achieve.

In total, eighteen snail gut samples were sequenced across the three developmental categories. The first major finding concerned alpha diversity, a measure of how many different fungal taxa are present within a single sample and how evenly they are distributed. Adult snails harboured significantly lower fungal diversity in their guts than juveniles did. This pattern is intriguing because it runs counter to what is often observed in some animal microbiomes, where diversity accumulates with age as hosts encounter more environmental microbes. In the giant African snail, maturation appears to be accompanied by a winnowing of the fungal community, suggesting that adult physiology, diet, or immune defences may actively shape which fungi can persist.

Alpha diversity tells only part of the story, however. The researchers also examined beta diversity, which asks whether the composition of communities differs between groups of samples. Principal coordinates analysis, or PCoA, a statistical visualization technique that plots samples based on the similarity of their microbial profiles, revealed clear separation among the fungal communities associated with different developmental categories. To confirm that this visual separation was not an artefact of sampling noise, the team applied PERMANOVA, a permutation-based test of differences between groups. The result was statistically significant: the developmental categories genuinely differed in the makeup of their gut fungal communities. In other words, a juvenile snail and an adult snail collected from the same environment carry measurably different fungal passengers in their digestive tracts.

Zooming in on which fungi were actually present, the study found that the phylum Ascomycota dominated the mycobiome across all developmental categories. This is perhaps unsurprising, as Ascomycota is the largest fungal phylum and includes many yeasts and moulds that thrive in soil, decaying plant matter, and the leafy vegetation that snails consume. But the taxonomic composition was not uniform across life stages. Using two complementary statistical tools, LEfSe and DESeq2, the researchers identified taxa whose relative abundance differed significantly between developmental categories. LEfSe, which stands for linear discriminant analysis effect size, pinpoints taxa that explain differences between groups, while DESeq2 applies a rigorous statistical framework originally developed for gene expression data to detect differentially abundant features. Together, these methods produced a ranked list of fungal species associated with each developmental stage.

The SIMPER analysis, short for similarity percentage, added another layer of interpretation by identifying which taxa contributed most to the overall dissimilarity between developmental groups. Three species stood out: Synchytrium taraxaci, Aspergillus flavus, and Cladosporium cladosporioides. Each of these fungi has an interesting ecological profile. Synchytrium taraxaci is a chytrid-like parasite of dandelions and other plants, hinting that snail diet leaves a fungal fingerprint in the gut. Aspergillus flavus is a widespread mould famous for producing aflatoxins in contaminated crops, raising questions about what role, if any, it plays in the snail’s internal environment. Cladosporium cladosporioides is an ubiquitous saprophytic fungus found on plants and in air worldwide. The authors are careful to note that these taxa should be interpreted as contributors to community dissimilarity rather than as causal drivers of the developmental differences. This is an important distinction: the cross-sectional design of the study shows association, not causation, and the researchers are explicit that host development itself has not been proven to cause the observed shifts.

Beyond simply listing which fungi were present, the team explored how the fungal taxa might relate to one another inside the gut. Co-occurrence network analysis constructs a map of statistically inferred associations, linking taxa that tend to appear together across samples. Within this inferred network, six taxa emerged as highly connected hubs: Hanseniaspora uvarum, Apiospora montagnei, Aureobasidium thailandense, Colletotrichum aenigma, Truncatella angustata, and Calonectria ilicicola. Hub taxa in microbial networks are often considered ecologically influential because their abundance patterns correlate with many other species, suggesting they may occupy central positions in the community’s structure. Hanseniaspora uvarum, for example, is a yeast commonly associated with fruits and fermentation, while Colletotrichum aenigma is a plant pathogen. Whether these fungi are actively shaping the gut environment or simply co-occurring because of shared dietary sources remains an open question, but their centrality makes them prime candidates for future functional studies.

Why does any of this matter beyond the world of snail microbiology? The answer lies in the snail’s role as an intermediate host of Angiostrongylus cantonensis. Humans acquire the parasite by eating raw or undercooked snails, or contaminated vegetables carrying snail mucus, and the resulting eosinophilic meningitis can be severe and occasionally fatal. The parasite’s development within the snail depends on the internal conditions of its host, and there is growing appreciation in parasitology that host microbiomes can modulate parasite establishment, development, and transmission. Bacterial communities have already been implicated in such interactions in other host-parasite systems. By establishing that the fungal community also varies systematically with host development, this study lays the groundwork for asking whether gut fungi influence how successfully the rat lungworm develops inside its snail host, or whether particular fungal profiles make certain snails more competent vectors than others.

The authors are appropriately measured in their conclusions. Because the snails were sampled at a single point in time and grouped by developmental category, the study cannot disentangle whether the fungal differences are driven by host age, by diet changes across life stages, by the environments different-aged snails occupy, or by some combination of these factors. Longitudinal studies following individual snails from hatchling to adult, ideally under controlled laboratory conditions with standardized diets, would be needed to establish causation. Nevertheless, the identified developmental-category-associated taxa and the highly connected network hubs provide a concrete starting point. They give researchers a shortlist of fungal species to target in experiments, and they establish a reference baseline against which future mycobiome studies of A. fulica, whether conducted in other geographic regions or in the context of parasite infection, can be compared.

The study also fills a genuine gap in the broader literature on molluscan holobionts, the term used to describe a host and its full community of associated microorganisms. While the gut bacterial microbiomes of many invertebrates, including snails, have been extensively characterized, fungal communities have been largely overlooked, particularly in invasive species of medical and agricultural importance. As sequencing costs fall and metagenomic methods mature, the fungal dimension of host biology is attracting renewed attention across ecology and infectious disease research. For the giant African snail, an animal whose global spread continues to accelerate with trade and climate change, understanding every component of its internal ecosystem, from bacteria to fungi to the parasites they may influence, is increasingly viewed as essential to predicting and managing its public health impact. This first detailed portrait of the snail’s gut mycobiome is a modest but meaningful step in that direction, and it signals that the invisible fungal world inside one of the world’s most notorious invasive pests is far more dynamic than anyone had previously documented.

Subject of Research: Gut mycobiome variation across developmental stages of the giant African snail Achatina fulica, an intermediate host of Angiostrongylus cantonensis

Article Title: Metagenomic analysis of developmental-category-associated fungal communities in the gut contents of Achatina fulica, an intermediate host of Angiostrongylus cantonensis

Article References: He, P., Zhang, K., Khan, J., Ouyang, H., Hu, S., Qian, S., Shu, B., Li, X., & Lin, D. (2026). Metagenomic analysis of developmental-category-associated fungal communities in the gut contents of Achatina fulica, an intermediate host of Angiostrongylus cantonensis. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07722-5

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07722-5

Keywords: Achatina fulica, gut mycobiome, metagenomics, Angiostrongylus cantonensis, developmental stages, Ascomycota, invasive species, fungal ecology, Parasites & Vectors, eosinophilic meningitis, co-occurrence networks, Guangzhou