The research, led by Xuan Dong of the Yellow Sea Fisheries Research Institute at the Chinese Academy of Fishery Sciences together with Weifeng Shi of Shanghai Jiao Tong University School of Medicine and a large international team, drew on an unusually rich collection of 403 samples gathered over six years, from 2019 through 2024. Sampling spanned a remarkable geographic range: the seas near the Antarctic Peninsula and the South Shetland Islands, the South Orkney Islands, and South Georgia Island in Western Antarctica, along with the Cosmonauts Sea in Eastern Antarctica. Specimens were collected with the assistance of the crews of the research icebreakers Xuelong and Xuelong 2 and scientific observers working with the Chinese krill fishery, an arrangement that allowed the team to reach remote waters across multiple seasons.

Technically, the study relied on metatranscriptomic sequencing, an approach that captures the total RNA present in a sample rather than targeting a single gene or organism. Because RNA viruses must replicate through RNA intermediates, sequencing the transcriptomes of host tissues and associated microbes simultaneously surfaces viral genomes that would be missed by DNA-based methods. The team screened the resulting data using RdRp-scan, a pipeline built around hidden Markov model profiles that detect the RNA-dependent RNA polymerase, the hallmark enzyme conserved across RNA virus lineages. Candidates passing initial screening were then subjected to increasingly conservative validation criteria, including DIAMOND-based similarity searches, to distinguish genuine viral polymerases from cellular genes or sequencing artifacts. This two-tier strategy, combining a sensitive discovery scan with a stringent confirmation analysis, allowed the researchers to characterize both complete viral genomes and highly fragmented sequences that hint at even more diversity lurking in the data.

The viral inventory that emerged was dominated by positive-sense single-stranded RNA viruses, with 37 representatives, a group that includes many of the most familiar virus families infecting animals and plants. Sixteen double-stranded RNA viruses and five negative-sense single-stranded RNA viruses rounded out the collection. Among the named discoveries were Lawrence virus and Vespucci virus, along with a member of the Picornaviridae, a family that includes poliovirus and foot-and-mouth disease virus among its terrestrial relatives. The sheer proportion of novel agents underscores how little is known about viral life in polar ecosystems, where cold, ice-covered waters and isolated food webs may have fostered long, independent evolutionary histories for their microbial inhabitants.

To understand how these viral communities are organized, the researchers applied alpha and beta diversity analyses, standard ecological tools for measuring within-sample richness and between-sample compositional differences. The alpha diversity comparisons, whether based on RdRp-scan results or the more stringent dataset, showed no statistically significant differences in viral richness or Shannon diversity across host species or sampling locations, with one-way ANOVA yielding p-values above 0.05 in every comparison. In other words, no single host or site carried a categorically richer virome than another. Beta diversity told a different story: the composition of viral communities differed significantly among host species, indicating that host identity, not geography, is the dominant force structuring which viruses live where. The authors note that the influence of geographic location on virome composition warrants further study, particularly given the wide and seasonally variable sampling range.

The most consequential finding, however, came from comparing viral sequences across the Antarctic food web. The team detected near-identical strains of Lawrence virus, sharing 99.35 percent identity in the RNA-dependent RNA polymerase gene, in both Antarctic krill and their predators. Vespucci virus strains found in krill and fish shared 97.70 to 99.08 percent RdRp identity with sequences from the same predators, and a picornavirus showed a similar pattern. The predators in question were the chinstrap penguin, Pygoscelis antarcticus, and the Antarctic fur seal, Arctocephalus gazella, two species that feed heavily on krill and fish in the Southern Ocean. Such high sequence identity between viruses found in prey and their consumers is suggestive of cross-species transmission moving up the food chain, although the authors are careful to frame this as a potential route rather than a proven one.

Antarctic krill, Euphausia superba, sit at the center of this transmission story for good reason. The shrimp-like crustacean is among the most abundant animals on the planet by biomass and forms the dietary backbone for penguins, seals, whales, and countless fish species. Any virus capable of persisting in krill populations has, in principle, a ready-made vehicle for reaching a wide range of vertebrate hosts through predation. The near-identical viral sequences in krill, fish, penguins, and fur seals provide the first genomic evidence that this trophic pathway may carry RNA viruses between distantly related animals in the Southern Ocean, a dynamic that has been hypothesized for other ecosystems but rarely documented in polar waters.

Beyond its ecological implications, the study carries practical weight for biosecurity. Warming temperatures and expanding human activity, from tourism to fisheries to scientific operations, are increasing the movement of people, equipment, and potentially pathogens into and out of the Antarctic. At the same time, shifting sea ice and changing prey distributions may alter contact patterns among wildlife species, creating new opportunities for viral exchange. The authors position their dataset as an essential baseline for assessing these risks, arguing that understanding which viruses currently circulate in Antarctic aquatic animals is a prerequisite for detecting any future incursions or range expansions. The evolutionary adaptability of RNA viruses, whose high mutation rates allow rapid adjustment to new hosts and conditions, makes this baseline all the more urgent to establish.

The work also demonstrates how modern genomic surveillance can be extended to environments where traditional virology has struggled to gain a foothold. Cold-chain logistics, remote fieldwork, and the difficulty of culturing polar pathogens have long limited virus discovery in Antarctica, but metatranscriptomics sidesteps many of these barriers by reading viral genetic material directly from field samples. The detection of 160 distinct RNA-dependent RNA polymerase groups in the broader screening analysis, many of them recurring across multiple libraries, suggests that the 58 fully characterized viruses represent only a portion of the diversity present. As sequencing costs continue to fall and reference databases expand, similar surveys in other polar and deep-sea ecosystems are likely to reveal comparable hidden reservoirs.

For now, the study stands as a reminder that even the planet’s most isolated continent is not virologically empty. Its waters host a diverse and largely novel array of RNA viruses, shaped primarily by the hosts they infect and connected to top predators through the food they eat. Whether any of these agents pose risks to wildlife health, fisheries, or human activity remains an open question, but the answer will depend on the kind of systematic, multi-year surveillance this research exemplifies. With the Southern Ocean changing faster than almost any marine environment on Earth, cataloging its viral inhabitants before the ecosystem shifts further may prove to be one of the most time-sensitive tasks in polar science.

Subject of Research: Diversity and food-web transmission of RNA viruses in Antarctic aquatic animals

Article Title: Underexplored diversity and transmission of RNA viruses in Antarctic aquatic animals

Article References: Dong, X., Zhou, Q., Luo, J., Su, Q., Wang, X., Zhu, J., Fan, G., Zhang, J., Ying, Y., Zhao, Y., Liu, L., Xu, Q., Liu, S., Wang, X., Li, J., Li, C., Yan, Y., Meng, F., Li, X., … Shi, W. (2026). Underexplored diversity and transmission of RNA viruses in Antarctic aquatic animals. Microbiome. https://doi.org/10.1186/s40168-026-02544-0

Image Credits: AI Generated

DOI: 10.1186/s40168-026-02544-0

Keywords: Antarctica, RNA viruses, virome, metatranscriptomics, Antarctic krill, chinstrap penguin, Antarctic fur seal, viral transmission, virus discovery, Southern Ocean, biodiversity, biosecurity