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The microbial communities of the hydrothermal Scaly-foot Snails (SFSs) from independent hydrothermal vent fields have not been investigated in depth. In this study, we collected SFSs from two different hydrothermal environments located on the Central Indian Ridge (CIR) and the Southwest Indian Ridge (SWIR), the Kairei and Longqi vent fields, respectively. Additionally, one SFS collected from the Kairei vent field was reared for 16 days with in situ deep-sea seawater. The epibiotic and internal samples of SFSs, including ctenidium, esophageal gland, visceral mass, shells, and scales, were examined for microbial community compositions based on the 16S rRNA gene. Our results revealed significant differences in microbial community composition between SFSs samples collected from Kairei and Longqi vent fields. Moreover, the microbial communities of epibiotic and internal SFS samples also exhibited significant differences. Epibiotic SFS samples were dominated by the bacterial lineages of Sulfurovaceae, Desulfobulbaceae, Flavobacteriaceae, and Campylobacteraceae. While in the internal SFS samples, the genus Candidatus Thiobios, affiliated with the Chromatiaceae, was the most dominant bacterial lineage. Furthermore, the core microbial communities of all samples, which accounted for 78 ∼ 92% of sequences, were dominated by Chromatiaceae (27 ∼ 49%), Sulfurovaceae (10 ∼ 35%), Desulfobulbaceae (2 ∼ 7%), and Flavobacteriaceae (3 ∼ 7%) at the family level. Based on the results of random forest analysis, we also found the genera Desulfobulbus and Sulfurovum were the primary bacterial lineages responsible for the dissimilarity of microbial communities between the SFS samples collected from the Kairei and Longqi vent fields. Our results indicated that the microbial lineages involved in the sulfur cycle were the key microorganisms, playing a crucial role in the hydrothermal vent ecosystems. Our findings expand current knowledge on microbial diversity and composition in the e

The hairy snails of the genus Alviniconcha are representative deep-sea hydrothermal vent animals distributed across the Western Pacific and Indian Ocean. Out of six known species in the genus Alviniconcha, only one nominal species of A. marisindica was found in the Indian Ocean from the Carlsberg Ridge (CR), Central Indian Ridge (CIR) to the northern part of Southwest Indian Ridge (SWIR) and Southeast Indian Ridge (SEIR). Recently, the Alviniconcha snails were found at three new vent fields, named Onnare, Onbada, and Onnuri, in the northern CIR, which promotes a more comprehensive phylogeographic study of this species. Here, we examined the phylogeography and connectivity of the Alviniconcha snails among seven vent fields representing the CR and CIR based on DNA sequence data of a mitochondrial COI gene and two protein-coding nuclear genes. Phylogenetic inferences revealed that the Alviniconcha snails of the newly found in the northern CIR and two vent fields of Wocan and Tianxiu in the CR were divergent with the previously identified A. marisindica in the southern CIR and mitochondrial COI data supported the divergence with at least greater than 3% sequence divergence. Population structure analyses based on the three genetic markers detected a phylogeographic boundary between Onnuri and Solitaire that divides the whole snail populations into northern and southern groups with a low migration rate. The high degree of genetic disconnection around the 'Onnuri' boundary suggests that the Alviniconcha snails in the Indian Ocean may undergo allopatric speciation. The border may similarly act as a dispersal barrier to many other vent species co-distributed in the CIR. This study would expand understanding the speciation and connectivity of vent species in the Indian Ocean.

Second mission to scale deep mountains announced.