Responeses Of Apostichpus Japonicus (Selenka) To Chemical Stress Factrs And Physiolical And Ecological Mechanism

The effects of ammonical nitrogen, nitrite, and heavy metals on the growth, survival, metabolism and metabolic enzymes of sea cucumber, Apostichopus japonicus (Selenka) were studied by the responses of physiological ecology to some chemical stress factors. The security concentrations of some pollutants to sea cucumber were sured and the detoxification mechanism of sea cucumber to ammonical nitrogen, nitrite, heavy metals were primary Studied. The results are as follows:1 The Effects of Ammonical Nitrogen on the Growth, Survival, Metabolism and Metabolic Enzymes in Sea Cucumber, Apostichopus Japonicus (Selenka)The effects of acute and chronic ammonical nitrogen on the growth, survival, metabolism and metabolic enzymes in sea cucumber were studied by the method of experimental ecology. The results demonstrated that the tolerance of sea cucumbers in three body sizes to ammonical nitrogen were increased with the increasing body size and decreased with increasing ammonical nitrogen concentration and time for those individuals exposed to acute nitrite stress. The median lethal concentrations(LC50)of ammonical nitrogen at 24 h, 48 h, 72 h and 96 h to sea cucumbers in three body sizes (wet body weights, 3.47±1.02, 50.50±1.67and 103.17±3.82g ) were 420.73,179.89,118.30,77.62 mg/L;509.33,188.80,105.20,83.37 mg/L and 549.50,299.23,126.77,90.57mg/L, respectively. And the safety concentrations (SC) of ammonical nitrogen for the sea cucumber in three body sizes at 96 h were 7.76,8.337 and 9.06 mg/L, respectively. The oxygen consumption rate of sea cucumbers demonstrated a trend to increase with increasing ammonical nitrogen concentration firstly, then drop significantly after exposing to acute ammonical nitrogen stress for 96 h. The responses of metabolic enzymes to ammonical nitrogen stress of see cummber in different tissues are different and have some tissue specificity. With the increase of ammonical nitrogen concentration, the hexokinase (HK) activity of respiratory trees, intestines and body walls in sea cucumber increased firstly, then drop gradually after exposing to acute ammonical nitrogen stress. The pyruvate kinase(PK) activity showed a trend of down-up-down. And the malic dehydrogenase (MDH) activity of respiratory trees, intestines and body walls in sea cucumber increased firstly, then drop gradually. When exposed to twenty days'chronic ammonical nitrogen stress, the Specific Growth (SGR) of sea cucumber was inhibited significantly with the increase of ammonical nitrogen concentration. (P<0.05).The oxygen consumption of sea cucumber exposed to chronic ammonical nitrogen stress for 20 d. ( wet body weights 50.50±1.67g ) showed the same trend with those exposed to acute ammonical nitrogen stress, which reached the peak value when ammonical nitrogen concentration at 5.09 mg/L.2 The Effects of Nitrite on the Survival, Metabolism and Growth of Sea Cucumber, Apostichopus Japonicus (Selenka)The effects of nitrite on the survival, metabolism and growth of sea cucumber were studied by the method of experimental ecology. The experiments were carried out from June to August 2009.The results demonstrated that the tolerance of sea cucumbers in three body sizes to nitrite were increased with the increasing body size and decreased with increasing nitrite concentration and time for those individuals exposed to acute nitrite stress. The median lethal concentrations(LC50)of nitrite at 24 h, 48 h, 72 h and 96 h to sea cucumbers in three body sizes (wet body weights, 2.91±0.19, 48.96±0.88 and 102.54±3.33g ) were 377.57, 251.19, 144.21 and 100.00mg/L,575.44, 371.54, 245.5 and 195.43mg/L, and 790.69, 492.04, 309.74 and 277.33mg/L, respectively. And the safety concentrations (SC) of nitrite for the sea cucumber in three body sizes at 96 h were 10.00,19.54 and 27.70mg/L, respectively. The oxygen consumption rate of sea cucumbers demonstrated a trend to increase with increasing nitrite concentration firstly, then drop significantly after exposing to acute nitrite stress for 96 h. When exposed to twenty days'chronic nitrite stress, the oxygen consumption of sea cucumber ( wet body weights 48.96±0.88g ) showed the same trend with those exposed to acute nitrite stress, which reached the peak value when nitrite concentration at 5.75mg/L. The Specific Growth (SGR) of sea cucumber was inhibited significantly when exposed to chronic nitrite stress as well (P<0.05).3 The Effects of Heavy Metals on the Growth, Survival, Metabolism and Metabolic Enzymes in Sea Cucumber, Apostichopus Japonicus (Selenka)The effects of heavy metals on the growth, survival, metabolism and metabolic enzymes in sea cucumber (wet body weights, 15.42±2.07g) were studied in the experiments. The results demonstrated that the tolerance of sea cucumbers to three heavy metals were all decreased with increasing the concentration of heavy metal and time for those individuals exposed to acute stress. The degree of the toxicity is in the order of Cu²⁺>Cd²⁺>Zn²⁺. The median lethal concentrations(LC50)of Cu²⁺,Cd²⁺,Zn²⁺ at 24 h, 48 h, 72 h and 96 h to sea cucumbers were 0.468,0.267,0.153,0.133 mg/L,4.446,3.206,2.250,1.574 mg/L and 7.691,5.200,3.467,2.679 mg/L, respectively. And the safety concentrations (SC) of them for the sea cucumber at 96 h were0.013,0.157 and 0.268mg/L, respectively. Besides the acute Zn²⁺ stress at the concentration of 1.00mg/L was increased observably, the oxygen consumption rate of sea cucumbers was decreased gradually with increasing concentration of other treatments. When exposed to twenty days'chronic heavy metal stress, the oxygen consumption of sea cucumber demonstrated a trend to decrease with increasing the concentration of heavy metal firstly, then increase significantly. The Specific Growth (SGR) of sea cucumber was inhibited significantly when exposed to chronic heavy metal stress (P<0.05). The variation tendency of the pyruvate kinase(PK) activity and the hexokinase (HK) activity in respiratory trees, intestines and body walls are similar when sea cucumber exposed to chronic heavy metal stress. But the specific changes are different because of the type of heavy metal and the difference of tissues in sea cucumber. In general speaking, the pyruvate kinase(PK) activity of three tissues reached the peak value after dropping the lowest firstly, then with the increase of Zn²⁺,Cu²⁺ and Cd²⁺ concentrations, the activity reduced gradually.The hexokinase (HK) activity showed the same trend with PK.