Comparison of microbial assemblages associated with the stalked barnacle Neolepas marisindica from two adjacent hydrothermal vent fields on the Central Indian Ridge.

Neolepas marisindica, a stalked barnacle endemic to the Central Indian Ridge (CIR), hosts microbial communities that remain poorly characterized. In this study, we performed 16S rRNA amplicon sequencing to characterize the microbiome associated with N. marisindica collected from two geographically adjacent hydrothermal vent fields along the Central Indian Ridge (CIR): Solitaire (Site A) and Onnuri (Site D). We further used PICRUSt2 to infer the functional potential of these microbial communities and to assess whether differences in in situ geochemical conditions between the two vents shape microbiome composition and metabolic capacity. Both sites harbored microbiota dominated by Proteobacteria, yet displayed distinct taxonomic and functional differences. Site D was enriched in methanotrophic genera (Methylobacter, Methylomicrobium), while Site A was dominated by sulfur-oxidizing taxa such as Thiotrichaceae. Although alpha diversity was higher at Site D, the difference was not statistically significant. Beta diversity analysis showed clear clustering by site. Functional prediction using PICRUSt2 revealed elevated pathways for oxidative phosphorylation, lipid metabolism, and secondary metabolite biosynthesis in Site D samples, suggesting adaptation to methane-rich conditions. LEfSe analysis supported these site-specific functional patterns. Overall, this study reveals both a shared microbial core and localized differences in microbiome structure and function in N. marisindica, underscoring the influence of geochemical variation on host-associated microbiota in deep-sea hydrothermal ecosystems.