Effects of water salinity on the antioxidant enzyme activities and growth of clam Cyclina sinensis

In order to clarify the effects of water salinity on the growth and immune enzymes of clam Cyclina sinensis,and accordingly,to explore the possibility of breeding C.sinensis in different salinity environment,the individuals of the clam were undergone different salinity stress(10,15,25(control),and 35),with the antioxidant enzymes superoxide dismutase(SOD) and catalase(CAT) in gill,mantle,and hepatopancreas at 0,3,6,12,24,48,and 96 h of salinity stress measured respectively.The monthly length-and weight gain rates were also measured after the individuals cultured under different salinity stress for two months.In different tissues of the clam,hepatopancreas had the highest antioxidant enzyme activities,followed by mantle,and gill.For the individuals under salinity 10,the SOD activity in gill at 3 h and in mantle and hepatopancreas at 3,6,12,and 24 h,as well as the CAT activity in mantle at 6 and 12 h and in hepatopancreas at 3 and 6 h,was significantly higher than that of the control(P 0.05);for the individuals under salinity 15,only the SOD and CAT activities in hepatopancreas at 3 h were significantly higher than those of the control(P0.05);whereas for the individuals under salinity 35,the SOD activity in gill at 3 and 6 h,in mantle at 3,6,12,and 24 h,and in hepatopancreas at 0,3,6,12,24,48,and 96 h,as well as the CAT activity in gill at 3 h,in mantle at 3,6,12,and 24 h,and in hepatopancreas at 3,6,24,48,and 96 h,was significantly higher than that of the control(P 0.05).In addition,the variation extents of the SOD and CAT activities under salinity 35 were significantly higher than those under salinity 10(P0.05).The length-and weight gain rates of the individuals under salinity 15 were greater,but had no significant differences with the control,and also,had no differences between the first month and the second month(P0.05).Under salinity 10,the length-and weight gain rates were significantly lower than those under salinity 15 and of the control,and had significant differences between the first and second months(P0.05).Under salinity 35,both the length gain rate and the weight gain rate were the lowest,and had no significant differences between the first and second months.In conclusion,when stressed by salinity,the C.sinensis should take about 24 h for the restoration of its antioxidant enzyme activities.C.sinensis had a stronger tolerance against low salinity than against high salinity.When the salinity was at 35,the antioxidant enzyme activities of the clam varied greatly,and the growth was almost stopped.