Two new gastropod holobionts from Atlantic hydrothermal vents showing different levels of endosymbiosis dependence
- 1Ifremer
Abstract
Chemosynthetic symbioses underpin animal life at deep-sea hydrothermal vents, encompassing substantial variabilities in symbiont identity, metabolic capacity, and host dependence. Here, we characterise symbioses in two peltospirid snails from Mid-Atlantic Ridge vents, Peltospira gargantua and P. smaragdina, using 3D anatomical reconstruction, stable isotope analyses, fluorescence in situ hybridization, transmission electron microscopy, and metagenomics. Both species hosted abundant intracellular Campylobacterota within bacteriocytes of a hypertrophied oesophageal gland. Their dominant symbionts belonged to genus Sulfurimonas, but the two hosts were associated with distinct symbiont lineages. Symbiont genomes encoded carbon fixation through the rTCA cycle, sulfide oxidation, and Group I Ni-Fe hydrogenases, indicating combined thiotrophic and hydrogenotrophic capacities. Hydrogenase copy number varied across vent fields from one to three copies. The P. gargantua symbiont from the hydrogen-enriched Hydra vent field carried two divergent copies, including one with a truncated catalytic region, potentially reflecting local adaptation to vent geochemistry. Anatomical and isotopic comparisons further revealed contrasting host dependence, with P. gargantua having a proportionally larger oesophageal gland and ventricle coupled with a reduced radula, as well as a greater nitrogen-isotope enrichment between symbiotic and non-symbiotic tissues. The smaller oesophageal gland and larger feeding apparatus of P. smaragdina point to it being mixotrophic. Previously, all known peltospirid symbioses have partnered with Gammaproteobacteria, and we expand the known diversity of peltospirid symbioses. Our findings underscore how closely related hosts can exhibit different degrees of dependence on symbiosis, and that mixotrophic symbiosis may be prevalent in small vent species previously thought to be non-symbiotic.
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BibTeX
@misc{methou2026gastropod,
title = {{Two new gastropod holobionts from Atlantic hydrothermal vents showing different levels of endosymbiosis dependence}},
author = {P. Methou and X. Nie and O. Rouxel and L. N. Michel and M. Zbinden and V. Cueff-Gauchard and J. Aube and A. Ampuero and M. Matabos and J. D. Sigwart and C. Cathalot and T. Giunta and C. Chen and M.-A. Cambon and J. Sun},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.05.756691},
url = {https://www.biorxiv.org/content/10.64898/2026.10.05.756691v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Two new gastropod holobionts from Atlantic hydrothermal vents showing different levels of endosymbiosis dependence
AU - P. Methou
AU - X. Nie
AU - O. Rouxel
AU - L. N. Michel
AU - M. Zbinden
AU - V. Cueff-Gauchard
AU - J. Aube
AU - A. Ampuero
AU - M. Matabos
AU - J. D. Sigwart
AU - C. Cathalot
AU - T. Giunta
AU - C. Chen
AU - M.-A. Cambon
AU - J. Sun
PY - 2026
DA - 2026/10/05
PB - bioRxiv
DO - 10.64898/2026.10.05.756691
UR - https://www.biorxiv.org/content/10.64898/2026.10.05.756691v1
AB - Chemosynthetic symbioses underpin animal life at deep-sea hydrothermal vents, encompassing substantial variabilities in symbiont identity, metabolic capacity, and host dependence. Here, we characterise symbioses in two peltospirid snails from Mid-Atlantic Ridge vents, Peltospira gargantua and P. smaragdina, using 3D anatomical reconstruction, stable isotope analyses, fluorescence in situ hybridization, transmission electron microscopy, and metagenomics. Both species hosted abundant intracellular Campylobacterota within bacteriocytes of a hypertrophied oesophageal gland. Their dominant symbionts belonged to genus Sulfurimonas, but the two hosts were associated with distinct symbiont lineages. Symbiont genomes encoded carbon fixation through the rTCA cycle, sulfide oxidation, and Group I Ni-Fe hydrogenases, indicating combined thiotrophic and hydrogenotrophic capacities. Hydrogenase copy number varied across vent fields from one to three copies. The P. gargantua symbiont from the hydrogen-enriched Hydra vent field carried two divergent copies, including one with a truncated catalytic region, potentially reflecting local adaptation to vent geochemistry. Anatomical and isotopic comparisons further revealed contrasting host dependence, with P. gargantua having a proportionally larger oesophageal gland and ventricle coupled with a reduced radula, as well as a greater nitrogen-isotope enrichment between symbiotic and non-symbiotic tissues. The smaller oesophageal gland and larger feeding apparatus of P. smaragdina point to it being mixotrophic. Previously, all known peltospirid symbioses have partnered with Gammaproteobacteria, and we expand the known diversity of peltospirid symbioses. Our findings underscore how closely related hosts can exhibit different degrees of dependence on symbiosis, and that mixotrophic symbiosis may be prevalent in small vent species previously thought to be non-symbiotic.
ER -