title: Several deep-sea mussels and their associated symbionts are able to live both on wood and on whale falls.
abstract: Bathymodiolin mussels occur at hydrothermal vents and cold seeps, where they thrive thanks to symbiotic associations with chemotrophic bacteria. Closely related genera Idas and Adipicola are associated with organic falls, ecosystems that have been suggested as potential evolutionary 'stepping stones' in the colonization of deeper and more sulphide-rich environments. Such a scenario should result from specializations to given environments from species with larger ecological niches. This study provides molecular-based evidence for the existence of two mussel species found both on sunken wood and bones. Each species specifically harbours one bacterial phylotype corresponding to thioautotrophic bacteria related to other bathymodiolin symbionts. Phylogenetic patterns between hosts and symbionts are partially congruent. However, active endocytosis and occurrences of minor symbiont lineages within species which are not their usual host suggest an environmental or horizontal rather than strictly vertical transmission of symbionts. Although the bacteria are close relatives, their localization is intracellular in one mussel species and extracellular in the other, suggesting that habitat choice is independent of the symbiont localization. The variation of bacterial densities in host tissues is related to the substrate on which specimens were sampled and could explain the abilities of host species to adapt to various substrates.
authors.affiliation: Département Systématique et Evolution, Muséum National d'Histoire Naturelle, UMR 7138 UPMC-IRD-MNHN-CNRS Systématique, Adaptation et Evolution, Equipe Espèces et Spéciation, CP 26, 57 Rue Cuvier, 75231 Paris Cedex 05, France. lorion@mnhn.fr
authors.forename: Julien
authors.initials: J
authors.lastname: Lorion
authors.forename: Sébastien
authors.initials: S
authors.lastname: Duperron
authors.forename: Olivier
authors.initials: O
authors.lastname: Gros
authors.forename: Corinne
authors.initials: C
authors.lastname: Cruaud
authors.forename: Sarah
authors.initials: S
authors.lastname: Samadi
mesh_terms: D000818:Animals; D001419:Bacteria / Q000145:classification / Q000648:ultrastructure; D001499:Bayes Theorem; D044822:Biodiversity; D004272:DNA, Mitochondrial / Q000737:chemistry; D017753:Ecosystem; D046529:Microscopy, Electron, Transmission; D049879:Mytilidae / Q000235:genetics / Q000382:microbiology / Q000502:physiology* / Q000648:ultrastructure; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013559:Symbiosis; D014907:Whales; D014934:Wood
chemical_list: D004272:DNA, Mitochondrial
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