Abstract:

Manila clam (Ruditapes philippinarum) is often exposed in air during the cultivation and transportation. In order to detect the physiological features of clams suffered from air exposure, we studied the changes of enzyme activities and immunity substances during air exposure and recovery stages. The gills and visceral masses were sampled at 12 h, 24 h and 48 h after air exposure and at 2 h, 6 h, 12 h and 24 h after recovery in sea water. The enzyme vitalities and the important immune related substances were tested by the kits, and the clams cultured in sea water all along were considered as controls. The AKP activities of the visceral mass in air exposed clams for 12 h and 24 h were significantly higher than those in control (P<0.05). CAT activities in visceral mass were not different from those of controls. AKP and CAT values in gills were relatively stable during the whole experiment. SOD values were significant higher in visceral mass at 12 h of air exposure, and in gills during recovery for 2 h. MDA levels were significantly higher in visceral mass at 24 h of air exposure, and lower in gills during recovery for 12 h and 24 h than those in controls. NO showed the maximum value at 6 h after recovery in visceral mass and at 48 h of air exposure in gill. According to the results, it is concluded that the antioxidation and immunization are exercised mainly by visceral mass during air exposure. And during recovery process, along with the recovery of respiration and circulation, the gill exercises the antioxidation to some extent, and then the clams quickly return to the normal physiological level.

Key words: Mudflat Aquaculture, Ruditapes philippinarum, Air Exposure, Enzyme Activity, Immunity Index, MDA, NO