Regionalized cell proliferation in the symbiont-bearing gill of the hydrothermal vent mussel Bathymodiolus azoricus

Bérénice Piquet (1, 2, 3) , François Lallier (3) , Coralie André (3) , Bruce Shillito (1) , Ann Andersen (3) , Sébastien Duperron (2)

1 BOREA - Biologie des Organismes et Ecosystèmes Aquatiques
2 MCAM - Molécules de Communication et Adaptation des Micro-organismes
3 ABICE - Adaptation et Biologie des Invertébrés en Conditions Extrêmes

Deep-sea mussels Bathymodiolus spp. harbor high densities of chemosynthetic bacterial symbionts located within their gill epithelial cells. Compared to non-symbiotic coastal mussel relatives of similar size, Bathymodiolus gills are considerably larger, a feature often considered an adaptation to symbiosis because it is related to the presence of intracellular bacteria in epithelial cells located in the lateral zone. In order to document the mechanisms underlying these sizes differences, this study compares gill cell proliferation patterns in Bathymodiolus azoricus and Mytilus edulis using microscopybased approaches. We used incubation experiments with a synthetic nucleotide (5-ethynyl 2'deoxyuridine, EdU), detectable throughout novel cell divisions, and phosphohistone H3 immunolabeling, a marker of mitosis. The results revealed proliferation areas in the ciliated zone and in the bacteria-loaded bacteriocytes located close to the frontal zone of gill filaments, swept by the incurrent sea-waterflow, and also in the dorsal region of gills in B. azoricus. Cell proliferation seems far less intensive in M. edulis. This study overall suggests high cell turnover and fast tissue dynamics in symbiont-bearing mussels.

Keywords: Phosphohistone H3; hydrothermal vents; cell division; chemotrophic symbiosis Aquarium; fluorescence microscopy; Bathymodiolus; EdU

Domains: Invertebrate Zoology

Bérénice Piquet, François Lallier, Coralie André, Bruce Shillito, Ann Andersen, et al.. Regionalized cell proliferation in the symbiont-bearing gill of the hydrothermal vent mussel Bathymodiolus azoricus. Symbiosis, 2020, 82, pp.225-233. ⟨10.1007/s13199-020-00720-w⟩. ⟨hal-03020135⟩