Effects of Acute Hyperosmotic Stress on Metabolic Rates and Immune-Related Enzymatic Activities in Clam (Trachycardium flavum)

Abstract:

To investigate the effects of acute hypersaline stress on the physiological metabolism and immunity of clam Trachycardium flavum. The oxygen consumption rate, ammonia excretion rate and activities of Na+/K+-ATPase, superoxide dismutase (SOD), acid phosphatase (ACP) and alkaline phosphatase (ALP) in different tissues were measured at 2, 12, 24, 48 and 72 h as water salinity increased from 31 to 37. Results showed that the oxygen consumption rate of clams in treatment group decreased at 2 h and then gradually increased, and was significantly higher than the control group at 24 and 72 h (P<0.05). The ammonia excretion rate significantly decreased (P<0.01) at 2 h and was lower than the control group at all time points. At 12 h, the clams showed significant lower Na+/K+-ATPase activity (P<0.05), but no significant difference of Na+/K+-ATPase activity in muscle was found between the control and treatment groups. SOD activities in mantle, hepatopancreas and gill reached maximum values at 24 h, which was significantly higher than the control group(P<0.05), and then decreased; SOD activity in muscle reached a peak at 48 h and then declined. ACP activity in mantle and gill showed similar variation as SOD. ACP activity was significantly reduced (P<0.05) and then gradually rose. No significant difference of enzymatic activity in muscle was found between the control and treatment groups. ALP activity in hepatopancreas and gill decreased followed by significant increase (P<0.05). Compared with the control group, no significant difference of enzymatic activity in mantle and muscle was found. The results suggested that acute hypersalinet stress significantly affected the metabolism and immunity of T. flavum, and such effects varied with time. The impact of hypersaline on the immune enzymatic activities is tissue-specific.