| The effects of acute and chronic toxicity of water-borne lead on Chinese sucker(Myxocyprinus asiaticus) were observed in artificial soft water (25mg CaCO3/L) at27.5℃. Firstly, the Pb exposure concentrations in acute toxicity experiment was carried out at0,0.1,0.2,0.3,0.4and0.5mg/L, and the median lethal concentration of M. asiaticus in96hours (96h LC50) was determined. Then, based on the result of96h LC50, the Pb exposure concentrations in chronic experiment was designed as0,10and50μg/L. After eight weeks of toxic treatment, the effects of different water-borne lead concentrations on the growth performance, metabolic capacity, antioxidant capacity, energy storage and the accumulation and distribution of lead in the tested fish were measured.The main results from this study as follows:1. In the acute exposure experiment, the mortality of M. asiaticus increased with increasing lead concentration. Using the method of a straight line interpolation the values of96h LC50and safe concentration (SC) of this fish were estimated as0.264and0.0264mg/L, respectively.2. During the8-week chronic exposure experiment, no mortality of the tested fish occurred in each group. The activity of GST and the level of T-AOC in hepatopancreas, gill and kidney of the tested fish increased with increasing lead exposure concentrations. The contents of MDA in hepatopancreas, gill and kidney of M. asiaticus increased with increasing the lead concentrations, and the contents of MDA in the three kinds of tissue in the group of50μg Pb/L were significantly higher than those in the control group (p<0.05). The glycogen content in hepatopancreas decreased with increasing lead exposure concentrations, and the value in the group of10μg Pb/L was significantly lower than that in the control (p<0.05). But for muscle glycogen there was no significant difference among the three groups.3. The resting metabolic rate increased with increasing lead exposure concentration. The resting metabolic rates in the groups of10and50μg Pb/L were138.29±4.52and150.21±2.11mgO2/h/kg, respectively, and each of them was significantly higher than that in the control group (p<0.05). The state3respiration rate of hepatopancreas mitochondria also increased with increasing lead exposure concentration. The state3respiration rate was27.00±3.94nmol O2/min/mg protein in the group of50μg Pb/L, which was significantly higher than that in the control group (p<0.05).4. The specific growth rate decreased with increasing lead exposure concentration, and the difference reached significant between the group of50μg Pb/L and the control group.5. The contents of lead in muscle and carcass increased with increasing lead exposure concentration, and the contents of lead in the each tissue in the group of50μg Pb/L were significantly higher than that in the control group (p<0.05). The content of lead in the carcass was higher than the muscle by the same concentration exposure, and the difference was significant in the group of50μg Pb/L.The conclusions suggested in this study were as follows:1. Compared to the most fish species in the reported literatures, the96h LC50with water-borne lead exposure in M. asiaticus was lower, which suggested that M. asiaticus have low tolerance for lead toxicity.2. The activity of GST and the level of T-AOC in hepatopancreas, gill and kidney of M. asiaticus increased with increasing lead exposure concentrations, but the food intake level and the content of hepatosomatic glycogen decreased with increasing lead exposure concentration. At the same time, the poisoned fish will increase the metabolic level to meet the energy expense for the extra physiological demands such as detoxification and antioxidant etc. Thus, the pattern of energy allocation in this fish was changed, and the energy supply for growth decreased, so that the growth of the fish was depressed. |
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