| The red swamp crayfish(Procambarus clarkia), native to the southern USA and northern Mexico, is a freshwater economic crustacean and has become one of the most important species in the world’s freshwater shrimp aquaculture industry. There are many studies focused on the biological characteristics, growth and reproduction, but we could hardly see reports about the physiological and behavioral response to environment factors caused by high-density cultivation. Based on principles and methods of physiological ecology and behavior ecology, this research focuses on the function of antioxidant system and feeding behavior of the red swamp crayfish under environment stress caused by ammonia nitrogen and nitrite, investigates the mechanism of environment factors on the crayfish and supplies the basic data for its cultivation. The main results are summarized as follows:1. At the same concentration of ammonia nitrogen, the activities of SOD and CAT in the hepatopancreas increased at first and then decreased gradually along with time, and the contents of MDA in the hepatopancreas was increased at first and then decreased in the lower concentration groups (10and20mg/L), and streamed upward in the higher concentration groups (30,40and50mg/L). At the same sample time of different ammonia nitrogen concentration, the activities of both enzymes at first rose and then fell with the increase of concentration except that they were gradually decreased at48th, and the contents of MDA increased with the increase of ammonia nitrogen concentration.2. During the process of gradual increase of ammonia nitrogen concentration (from O(control) to50mg/L), the activities of SOD and CAT in the hepatopancreas both increased at first and then decreased in the lower concentration groups, and gradually reduced in the higher concentration groups along with time prolonged; the contents of MDA in the hepatopancreas also increased at the beginning and then decreased in the lower concentration groups, and trended upward in the higher concentration groups besides another slight decrease in50mg/L group.3. At the same concentration of nitrite, the activities of SOD and CAT and the contents of MDA in the hepatopancreas increased at first and then decreased along with time prolonged, except that the activity of CAT decreased when the nitrite concentration was lOmg/L. At the same sample time of different nitrite concentrations, the activities of SOD and CAT first increased and then decreased with the increase of nitrite concentration, while the contents of MDA increased gradually.4. During the process of gradual increase of nitrite concentration (from0(control) to10mg/L), the activities of SOD and CAT in the hepatopancreas both increased at first and then decreased in the lower concentration groups, and gradually reduced in the higher concentration groups along with time prolonged; the contents of MDA in the hepatopancreas also increased at the beginning and then decreased in the lower concentration groups, and increased in the higher concentration groups.5. The two factors, ammonia nitrogen and nitrite, had similar effects on the feeding behavior. With the increase of concentration, the food intake, feeding time and feeding frequency of the crayfish represented a downtrend while the searching time trended upward gradually, and the moving time decreased at first and then slightly increased.The results suggest that, ammonia nitrogen and nitrite have significant effects on the function of antioxidant system and feeding behavior. The antioxidant enzymes were induced at first and then inhibited with the increase of the concentration and time. At the same time, the organism was harmed by the ammonia nitrogen and nitrite stress. And the feeding behavior was significantly inhibited. |
