Origin and development of germ cells in Crassostrea gigas oyster : relevance for controlled reproduction in hatchery

• Main Author: Fabioux, Caroline
• Other Authors: Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Le Pennec Marcel
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2004
• Subjects: germ cells; gametogenesis; controlled reproduction; Crassostrea; cellules germinales; gamétogenèse; oyster vasa-like gene; régulation; reproduction contrôlée; [SDV.BDLR]Life Sciences [q-bio]/Reproductive Biology; [SDV.MHEP.PHY]Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO]; Liliane; Vasa; Crassostrea gigas
• Online Access: https://tel.archives-ouvertes.fr/tel-00009344; https://tel.archives-ouvertes.fr/tel-00009344/document; https://tel.archives-ouvertes.fr/tel-00009344/file/tel-00009344.pdf

Membres du jury : Fostier Alexis, Favrel Pascal, Nonnotte Liliane, Goulletquer Philippe, Cochard Jean-Claude A comprehensive knowledge of Crassostrea gigas oyster reproduction processes is essential to optimize controlled reproduction in hatchery. This study aimed to determine the origin and the mechanisms of annual renewal of germ cells, still unknown in oysters, and the influence of temperature and photoperiod parameters on the regulation of the reproductive cycle. We characterized an orthologue of the vasa gene, the Oyvlg (Oyster vasa-like gene), the first germ cell specific marker isolated in molluscs. This marker was used to study C. gigas germline development. Oyster germ cells appeared specified during early development from mesentoblast 4d, as primordial germ cells (PGCs) determined by maternal cytoplasmic determinants, including Oyvlg mRNA. In adult oysters, the annual renewal of germ cells results from a proliferation of germinal stem cells (GSCs), self-renewing cells, scattered in the conjunctive tissue during the resting period. One-year experimental conditionings were realized to determine temperature and photoperiod parameter effects on oyster gametogenesis. Experimental conditionings consisted in (1) natural temperature and photoperiod conditions corresponding to Marennes-Oléron bay values, (2) accelerated conditions, twice faster than natural cycles and (3) constant wintering conditions adjusted to 8°C and 8 hours day-length. These analyses revealed a high plasticity of C. gigas reproduction since the rhythm of the reproductive cycle was entirely modelled by temperature and photoperiod variations. Decreasing photoperiod may regulate GSCs proliferation while low temperature (8°C-11°C) would enhance gonial mitosis and high temperature would accelerate germ cell maturation. As a result, manipulation of temperature and photoperiod conditions allows effective controlled reproduction all over the year. Le renouvellement annuel de la population de cellules germinales chez l'huître creuse Crassostrea ...