The faecal microbiota and its influence on fur seal (Arctocephalus sp.) physiology

The gastrointestinal microbiota is a key determinant of vertebrate physiology, metabolism, and adaptation, forming a dynamic holobiont system that supports host health and resilience. However, while the gut microbiota of several fur seal species has been described, most studies have focused primarily on taxonomic composition, leaving a major gap in understanding how microbial communities influence host physiology in marine mammals. This study provides the first comprehensive comparison of the faecal microbiota and blood metabolomic profiles of Australian (Arctocephalus pusillus doriferus) and New Zealand fur seals (A. forsteri) across age classes (adult vs. pup), integrating 16S rRNA gene sequencing, and untargeted metabolomics and untargeted lipidomics to examine host-microbe interactions.

Adult fur seals exhibited a conserved microbial structure dominated by the phyla Bacillota, Fusobacteriota, and Bacteroidota, while pups displayed lower microbial diversity and higher relative abundances of Actinobacteriota and Campylobacterota, alongside enrichment of metabolites involved in DNA synthesis (2-deoxy-D-ribose, 2-deoxycytidine, and 2-deoxyuridine) and lipid metabolism. Correlations between bacterial taxa and metabolites implicated in growth, fat deposition, and hair development suggest that it is possible that early-life microbial communities may play an important role in supporting rapid development and thermoregulation.

Despite logistical constraints inherent to field-based sampling of wild marine mammals, our findings demonstrate consistent microbial patterns within the Arctocephalus genus and clear age-related differences in blood metabolic profiles. Together, these results enhance understanding of the complex interplay between host development, diet, and microbial ecology in fur seals, and establish a foundation for future research into the functional significance of microbiota in marine mammal health and adaptation.

Not applicable.