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

Type Article
Date 2020-12
Language English
Author(s) Piquet Bérénice1, 2, 3, Lallier François H.1, André Coralie1, Shillito Bruce2, Andersen Ann C.1, Duperron Sebastien3, 4
Affiliation(s) 1 : Lab. Adaptation et Diversité en Milieu Marin, AD2M, Adaptation et Biologie des Invertébrés marins en Conditions Extrêmes (UMR 7144), ABICE, DYDIV, Station Biologique de Roscoff, Sorbonne Université CNRS, place Georges Teissier, Roscoff, France
2 : Laboratoire de Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), MNHN, CNRS-2030, IRD-207, Sorbonne Université, UCN, UA, Team: Adaptation aux Milieux Extrêmes (AMEX), 7 Quai Saint-Bernard, Paris, France
3 : Muséum National d’Histoire Naturelle, CNRS, Lab. Mécanismes de Communication et Adaptation des Micro-organismes (UMR 7245), Team: Cyanobactéries, Cyanotoxines et Environnement, CCE, PTME 12 rue Buffon, Paris, France
4 : Institut Universitaire de France, Paris, France
Source Symbiosis (0334-5114) (Springer Science and Business Media LLC), 2020-12 , Vol. 82 , N. 3 , P. 225-233
DOI 10.1007/s13199-020-00720-w
Keyword(s) Bathymodiolus, EdU, Phosphohistone H3, Hydrothermal vents, Cell division, Chemotrophic symbiosis

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 microscopy-based 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.

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