Global 16S rRNA diversity of provannid snail endosymbionts from Indo‐Pacific deep‐sea hydrothermal vents

Abstract

Symbioses between invertebrate animals and chemosynthetic bacteria build the foundation of deep-sea hydrothermal ecosystems worldwide. Despite the importance of these symbioses for ecosystem functioning, the diversity of symbionts within and between host organisms and geographic regions is still poorly understood. In this study we used 16S rRNA amplicon sequencing to determine the diversity of gill endosymbionts in provannid snails of the genera Alviniconcha and Ifremeria, which are key species at deep-sea hydrothermal vents in the Indo-Pacific Ocean. Our analysis of 761 snail samples across the distributional range of these species confirms previous findings that symbiont lineages are strongly partitioned by host species and broad-scale geography. Less structuring was observed within geographic regions, probably due to insufficient strain resolution of the 16S rRNA gene. Symbiont richness in individual hosts appeared to be unrelated to host size, suggesting that provannid snails might acquire their symbionts only during a permissive time window in early developmental stages in contrast to other vent molluscs that obtain their symbionts throughout their lifetime. Despite the extent of our dataset, symbiont accumulation curves did not reach saturation, highlighting the need for increased sampling efforts to uncover the full diversity of symbionts within these and other hydrothermal vent species.

Genomic patterns of divergence in the early and late steps of speciation of the deep-sea vent thermophilic worms of the genus Alvinella

“…Other genes under divergent selection are mostly unknown or involved in immunity and endocytosis and may affect the interaction of the worm with the associated campylobacteriadominated microbial assemblages covering its tube and its dorsal epidermis (i.e., trophic and detoxification role of the worm's epibiosis [65]). Microbial communities are likely to be genetically different between vent fields as previously observed for other vent taxa [66] and thus could induce co-evolutionary pathways of divergence in the worm's immune system [67]. In the specific cases of sympatric or parapatric speciation, genes under positive selection tend to be predominant among rapidly evolving genes [68].…”

“…, trophic and detoxification role of the worm’s epibiosis [ 65 ]). Microbial communities are likely to be genetically different between vent fields as previously observed for other vent taxa [ 66 ] and thus could induce co-evolutionary pathways of divergence in the worm’s immune system [ 67 ]. In the specific cases of sympatric or parapatric speciation, genes under positive selection tend to be predominant among rapidly evolving genes [ 68 ].…”

Genomic patterns of divergence in the early and late steps of speciation of the deep-sea vent thermophilic worms of the genusAlvinella

“…Other genes under divergent selection are mostly unknown or involved in immunity and endocytosis and may affect the interaction of the worm with the associated campylobacteria-dominated microbial assemblages covering its tube and its dorsal epidermis (i.e., trophic and detoxification role of the worm's epibiosis [72]). Microbial communities are likely to be genetically different between vent fields as previously observed for other vent taxa [73] and thus could induce co-evolutionary pathways of divergence in the worm's immune system [74]. In the specific cases of sympatric or parapatric speciation, genes under positive selection tend to be predominant among rapidly evolving genes [75].…”

“…, trophic and detoxification role of the worm’s epibiosis [72]). Microbial communities are likely to be genetically different between vent fields as previously observed for other vent taxa [73] and thus could induce co-evolutionary pathways of divergence in the worm’s immune system [74]. In the specific cases of sympatric or parapatric speciation, genes under positive selection tend to be predominant among rapidly evolving genes [75].…”

Ecological differences among hydrothermal vent symbioses may drive contrasting patterns of symbiont population differentiation

“…T. endoseptemdiera 16S rRNA V4-V5 hypervariable region. 250-bp paired-end amplicon libraries were prepared with degenerate primers after Walters et al [51], sequenced on an Illumina MiSeq platform at the Argonne National Laboratory (Lemont, IL, USA) and assessed for sequence variation with the U search -U noise [52] and O ligotyping [53] pipelines as in Breusing et al [54]. Fractional abundance plots of the final Ca .…”