Approches cellulaires et moléculaires de la gestion des réserves chez l’huître, Crassostrea gigas (Thunberg, 1793). Suivi saisonnier du métabolisme énergétique et effet du niveau trophique sur la mise en réserve

In the Pacific oyster, Crassostrea gigas, the energy necessary for general metabolism and gametogenesis is mainly provided by the glycogen stored in the vesicular cells. The first level of glycogen metabolism control is the entrance of glucose into cells. The monitoring of the uptake capacity of [U-14C] D-glucose revealed the existence of a saturable component with kinetic constants: Km = 0.71 mM ; Vmax = 0.22 nmol/h/106cells. The use of inhibitors has revealed the presence of carriers belonged to GLuT and SGLT types. A follow-up showed a seasonal variation of the uptake capacity and incorporation of glucose into glycogen, and a high expression of SGLT during mobilization of glycogen and gametes maturation. A bioassay in a controlled rearing system has shown the existence of a regulation of glucose incorporation and the expression of SGLT depending on the trophic level. In fasting situation, the storage capacity of glycogen is low while the expression of SGLT is high. A follow-up comparison of two strains of oysters selected from their resistance (R) or sensitivity (S) to summer mortality has been undertaken. Both strains show little variations in ntural environment, but under controlled conditions differences are observed in the sequence of the gametogenesis and their energy strategy, indicating a genetic origin to the difference R/S. Finally, cryopreservation has been envisaged to constitute a bank of cells. The adaptation of the protocol able to reach a survival rate of 68.5 ± 2.2 %.