Comparative analysis of gut viromes in four penguin species reveals diverse novel viruses and host-associated differences

Penguins, as distinctive marine birds, play important roles in polar and sub-Antarctic ecosystems, yet the diversity and species-specific distribution of their gut viromes remain insufficiently understood. Here, we used viral metagenomics to characterize the cloacal viromes of four penguin species— Spheniscus humboldti ( S. humboldti ), Pygoscelis papua ( P. papua ), Pygoscelis adeliae ( P. adeliae ), and Aptenodytes forsteri ( A. forsteri )—collected at Chimelong Ocean Kingdom. A total of 219 viral sequences representing potentially novel lineages were identified, with more than 94% sharing <80% amino acid similarity with previously known viruses. These sequences were assigned to several viral families, including Parvoviridae, Caliciviridae, Anelloviridae, Circoviridae, and Microviridae, among others. Marked interspecies differences in virome composition were observed: Parvoviridae dominated in S. humboldti , Microviridae were enriched in P. papua , Caliciviridae accounted for a substantial proportion in A. forsteri , and P. adeliae displayed the greatest overall virome diversity. Multiple-virus co-detections, particularly involving Parvoviridae, were frequent in S. humboldti . Phylogenetic analyses showed that many penguin-associated viruses clustered with viruses infecting other avian and fish hosts, suggesting possible dietary or environmental origins of some detected viral sequences. These findings expand current knowledge of penguin gut virome diversity and host-associated differences and provide a valuable foundation for evaluating the ecological roles, health implications, and transmission risks of penguin-associated viruses.