Normoxic and anoxic energy metabolism of the southern oyster drill Thais haemastoma during salinity acclimation: a direct calorimetric study

The energetic cost associated with salinity acclimation was determined in the marine gastropod Thais haemastoma by direct calorimetry under normoxic and anoxic conditions. Snails were collected from Caminada Pass near Grand Isle, Louisiana (Longitude 90 degree 2'W; Latitude 29 degree 2'N) in September 1987. Metabolic heat flux of snails acclimated to and measured at 10 or 30 ppt S was similar at 15.06 or 16.39 J/g dry wt/h, respectively, (corresponding to 0.76 or 0.83 ml O sub(2)/g dry flesh wt/h) under normoxic conditions, and 2.39 or 2.53 J/g dry wt/h under anoxic conditions. Inter-individual variability was high, obscuring the effect of salinity gradient on heat flux. When standardized to the pre-transfer control level of each individual under anoxic conditions, a significant increase (55%) of energy expenditure was observed for snails transferred to hyperosmotic conditions. In contrast, heat flux varied insignificantly in individuals in the anoxic 30 to 10 ppt S transfer.