Influence of sex and spawning status on oxygen consumption and blood oxygenation status in oysters Crassostrea gigas cultured in a Mediterranean lagoon (Thau, France)

The aim of this study was to characterize the respiratory activity (O2 consumption, O2 haemolymph status, cardiac-flow rate) of C. gigas cultivated in Thau lagoon water. The effects of season (summer and winter), sex and gametogenic cycle (pre-/post-spawning and resting status) were studied. Oxygen consumption was directly influenced by temperature and chlorophyll a abundance (season effect), whereas oxygenation of the haemolymph was not directly influenced by the Thau lagoon environmental factors studied in summer. For the first time in C. gigas, a difference in O2 consumption between sexes was measured. Indeed, male oysters had an O2 consumption twice that of female oysters. This difference could not be explained by a difference in gametogenic cycles between females and males. A difference in O2 consumption was also shown according to the gametogenic status for both female and male individuals. The reason for the increased O2 consumption by oysters in the post-spawning condition compared to pre-spawning condition is discussed.