Abstract: To clarify the effects of heat stress on the physiological metabolism and immune functions of Mytilus coruscus, we measured the clearance rate, oxygen consumption rate, ammonia excretion rate, hexokinase (HK), pyruvate kinase (PK), acid phosphatase (ACP), alkaline phosphatase (AKP), and superoxide dismutase (SOD) activities in different tissues of M. coruscus under different stress levels (from 20  ℃ to 25  ℃ and from 20  ℃ to 30  ℃). The results showed that the clearance rate increased to 0.56 L·g^-1·h^-1 at 25  ℃ for 3 h, but was not significantly different from the control group. The clearance rate was significantly reduced after 30  ℃. The mussel’s oxygen consumption rate and ammonia excretion rate were significantly increased when subjected to heat stress. Oxygen consumption rate was not different between 25 and 30  ℃ treatment, but the ammonia excretion rate was significantly lower at 30  ℃ than at 25  ℃. Compared with the control group, HK activity did not change in mantle and gill, but the HK activity in hepatopancreas was significantly decreased. HK activity was significantly higher in gill than in mantle and hepatopancreas. The PK activity was significantly increased after high temperature treatment, and peaked at 30  ℃, in contrast to a significant decrease of PK activity in gill at 30  ℃. A significant decrease in ACP activity in mantle was observed. The ACP activity in hepatopancreas was significantly decreased at 25  ℃, but ACP activity in gill did not change. The mantle’s AKP activity increased significantly at 25  ℃. In contrast, the gill’s and digestive gland’s AKP activity was significantly lowered at 30  ℃. The mantle’s SOD activity increased significantly at 30 ℃. SOD activity did not differ between gill and hepatopancreas. The hepatopancreas’s SOD activity was significantly lower than those in gill and mantle. Our results indicated that M. coruscus can adjust its metabolism level to cope with the heat stress under a certain range of temperature. Acute temperature increase could significantly affect its feeding, metabolism and immune function. The activities ofM. coruscus’ metabolic and immune-related enzymes are tissue specific.

Key words: Mytilus coruscus, heat stress, clearance rate, oxygen consumption rate, ammonia excretion rate, enzymatic activity.