Effects of salinity on digestive enzyme activity in Siganus guttatus

Effects of salinity on digestive enzyme activity in Siganus guttatus,body weight 86.09±17.99 g,total length 13.90±1.53 cm,were investigated.With seawater of salinity 30-32 as control group,we measured and compared activity of three kinds of digestive enzymes,protease,amylase and lipase in four digestive organs,pyloric caecum,ileum,stomach and liver of S.guttatus cultured at salinities 5,10 and 20 for 48 days respectively.Results showed that on the 24th day the pyloric caeca protease activity of salinity 20 group was lower than that of seawater(P0.05).On the 24th and 48th day,at the same salinity,the protease and amylase activity in descending order were as follows: pyloric caeca,intestine,stomach and liver;on the 48th day,the protease,amylase and lipase enzyme activity of salinity 20 group had no significant difference with those of the control group(P0.05);on the 24th and 48th day,at salinity 5,10,20 and seawater,the descending order of lipase activity were as follows: intestine,stomach,liver and pyloric caecum.The protease,amylase and lipase activity of salinity 10 and 5 group were lower than those of salinity 20 and control group,and had significant difference(P0.05),which indicated that low salinity inhibited digestive enzyme activity of S.guttatus.