| This study is divided into three parts: field investigation(Experiment 1) and laboratory process studies(Experiment 2 and Experiment 3). In experiment 1, during October and November in 2013 and 2014, total 278 specimens for 7 Siluriformes species were collected from the Luoqi section of the Yangtze River, the Beibei and Hechuan sections of the Jialing River, the Fuling sections of the Wu River. The Cr contents in every sample from the four sections were detected and analyzed. In experiment 2, channel catfish(Ictalurus punctatus) juveniles as experimental subjects to study water chromium exposure LC50 effect of channel catfish and research chromium exposure conditions, 28 days after the catfish liver, gill tissue using water exposure method cumulative case of chromium, liver, gills and muscle total antioxidant capacity(T-AOC), malondialdehyde(MDA), and brain cholinesterase(ACh E) activity in. In experiment 3, channel catfish(Ictalurus punctatus) juveniles as experimental subjects to study the effects of chromium on channel catfish growth conditions, the resting metabolic rate and metabolic related enzymes: lactate dehydrogenase, LDH, aspartate aminotransferase AST, changes in alanine aminotransferase ALT activity. The main results from experiment 1 were follows:(1) The majority of the whole fish samples were detected chromium. The mean content of Cr in the samples of Luoqi section ranged from 0.09-0.24 mg/kg, it means all of samples of the Luoqi section did not exceeded the limit value(2mg/kg) of the national safety criteria for food in China(GB2762-2012). The mean content of Cr in the samples of Hechuan section ranged from 0.06-0.15 mg/kg. The mean content of Cr in the samples of Beibei section ranged from 0.10-0.12 mg/kg. The mean content of Cr in the samples of Fuling section of Wu River ranged from 0.07-0.52 mg/kg, which all did not exceed.(2) The content of Cr in Pelteobagrus vachellii collected from all the sections was compared: Fuling section(0.52 ± 0.13 mg/kg) > Luoqi section(0.13 ± 0.01 mg/kg) > Hechuan section(0.12 ± 0.01 mg/kg) > Beibei section(0.10 ± 0.02 mg/kg). Fuling section was significantly higher than the other section of the river(p<0.05).The content of Cr in Silurus asotus and Hemibagrus macropterus collected from three sections was compared. The content of Cr in Silurus asotus: Luoqi section(0.13±0.02) > Hechuan section(0.11±0.02) > Fuling section(0.07±0.01). The content of Cr in Hemibagrus macropterus: Luoqi section(0.18±0.02) > Fuling section(0.07±0.01) > Hechuan section(0.06±0.01). The content of Silurus asotus in Fuling section was significantly lower than the other section of the river(p<0.05). The content of Hemibagrus macropterus in Luoqi section was significantly higher than the other section of the river(p<0.05).The content of Cr in Pelteobagrus nitidus collected from three sections was compared: Beibei section(0.12 ± 0.02 mg/kg) > Luoqi section(0.09 ± 0.02 mg/kg) > Hechuan section(0.06 ± 0.01 mg/kg). Beibei section of Jialing River was significantly higher than the other section of the river(p<0.05). The main results from experiment 2 were follows:(1) Exposure to water chromium channel catfish(Ictalurus punctatus) median lethal concentration(LC50) 96 h was 91.96 mg/L. After channel catfish exposure to the water chromium for 28 d, fish liver, gill tissue accumulation of chromium content increases as the concentration is increased, and the highest concentration of chromium cumulative volume group was significantly higher than other concentrations(p<0.05).(2) After channel catfish exposure to the water chromium for 28 d, brain ACh E activity decreased as the concentration is increased, and the ACh E activity of each concentration group were significantly lower than the control group(p<0.05); Effect on MDA of fish liver, gill and muscle tissue are: with the concentration, MDA content also increased, and the liver and muscle tissue at the highest concentration of MDA content was significantly higher(p<0.05); Effect on T-AOC levels of fish liver, gill and muscle tissue are: liver T-AOC level as the concentration showing a increased trend first and then decreased, and T-AOC level difference between groups was not significant, gill and muscle T-AOC level as the concentration showing a decreasing trend, and the highest concentration group T-AOC level was significantly lower than the control group(p<0.05). The main results from experiment 3 were follows:(1) After channel catfish(Ictalurus punctatus) exposure to water chromium for 28 d, final body weight of fish with elevated concentrations showed decreasing trend, and each concentrations of final body weight were significantly lower than the control group body weight; The fish resting metabolic rate increased as the concentration increased first and then decreased, and resting metabolic rate of lower concentration group was significantly higher(p<0.05).(2)Liver lactate dehydrogenase(LDH) activity increased as chromium concentration rises, and the highest concentration of LDH activity was significantly higher than other concentration groups(p<0.05); LDH activity with muscle tissue concentration showed a declining trend after the first rise, LDH activity of 29.196 mg/L concentration was significantly higher than other concentration groups(p<0.05); Aspartate aminotransferase(AST) activity of liver increases as the concentration is increased, and the highest concentration group AST activity was significantly higher than other groups(p<0.05), AST activity of muscle tissue showed a declining trend after the first rise, AST activity of 9.196 mg/L concentration group was significantly higher than control group(p<0.05); Alanine aminotransferase(ALT) activity of liver tissue only in the highest concentration group was significantly higher than the concentration of other groups(p<0.05). Muscle tissue ALT activity of every treatment group was significantly lower than the control group, but the difference in activity between the treatment groups was not significant. The conclusions suggested in this study were as follows:1. Siluriformes species from upstream of the Yangtze River and its branches were polluted by Cr in varying degrees, and within the same range of weight, the content of Hemibagrus macropterus in Luoqi section was significantly higher than the other section of the river.2. Exposure to water chromium channel catfish median lethal concentration(LC50) 96 h was 91.96 mg/L, described catfish heavy metal chromium tolerance is relatively high; after exposure 28 d, liver, muscle tissue chromium accumulation increased with concentration increased.3. Most studies found similar results, brain ACh E activity decreases as the concentration increases, indicating that the fish brain tissue by chromium poisoning; It suggested the MDA content of liver, gills and muscle tissue increases with the concentration increased, indicating that the body lipid peroxide content increased, liver T-AOC content increased first after the fall, indicating poison at low concentrations induced anti-body oxidation mechanism, but with concentration, antioxidant capacity hampered.4. After channel catfish exposure to water chromium for 28 d, the growth rate of the fish decline, indicating that it hinders the growth of channel catfish; at the same time, fish improve their metabolic capacity to provide antioxidant mechanisms required energy expense. |
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