| Two series of experiments were carried out in this study:field investigation and observation in laboratory.The experiment I was conducted on the contents and distribution of polycyclic aromatic hydrocarbons (PAHs) in the fishes from the upper reaches of the Yangtze River. From September to November in2010, the samples of10species were collected from the Zhuyang section of the Yangtze River, including Spinilbarbus sinensis, Pelteobagrus vachelli, Rhinogobio cylindricus, Cyprinus carpio, Carassius auratus, Siniperca kneri, Coreius heterodon, Coreius guichenoti, Mystus macropterus, and Silurus asotus. And the samples of6species were collected from the Fushun section of the Tuo River, a tributary of the Yangtze River, including Carassius auratus, Pelteobagrus fulvidraco, Cyprinus carpio, Siniperca kneri, Mystus macropterus, and Silurus asotus. The sample size for each fish species was3-11, totaling195. The contents of16polycyclic aromatic hydrocarbons (PAHs) in each sample were measured by the accelerated solvent extraction and gas chromatography. The experiment Ⅱ was conducted on effects of deitary phenanthrene (PHE, one of PAHs) on Spinibarbus sinensis in the laboratory conditions. Two treatments were carried out in this experiment. One was different levels of dietary PHE exposure. The tested fish was fed by experimental diets with different PHE contents (0,500,1000and1500μg/g) for16weeks. The other was different exposure time to dietary PHE. The diets containing0and1000PHE μg/g were used to feed the fish for0,1,3,7,14,28,42,56,84and112 days, respectively. The ability of anti-oxidative stress, hematological index, energy metabolism, growth performance and PHE accumulation were measured in the tested fish at each sampling time.The main results from experiment I were as follows:1. Various kinds of PAHs were detected in the10species of fish collected from the Zhuyang section of the Yangtze River. Spinibarbus sinensis had the highest total content of PAHs (ΣPAHs)[(2.91±0.45) μg/g], and Silurus asotus had the lowest ΣPAHs [(0.52±0.04) μg/g].2. Various kinds of PAHs were detected in the6species of fish collected from the Fushun section of the Tuo River. Carassius auratus had the highest ΣPAHs [(8.50±1.13) μg/g], and Silurus asotus had the lowest ΣPAHs [(1.30±0.07) μg/g].3. Comparing the five same species collected from the Zhuyang section to those from the Fushun section, each of the latter showed higher contents of ΣPAHs than its counterpart of the former, with significant differences in all pairs except Siniperca kneri. The fishes from the Fushun section contained a higher percentage of high-molecular-weight PAHs (HMW-PAHs), while those from the Zhuyang section contained higher percentages of low-molecular-weight PAHs (LMW-PAHs) and medium-molecular-weight PAHs (MMW-PAHs).The main results from experiment II were as follows:1. There were no significant differences in the number of red blood cells, hemoglobin and total protein in the serum among the different groups. Glucose content in the tested groups showed a "up-down" trend with increasing of the dietary PHE concentration, and that in each group exposed to dietary PHE was significantly higher than that in the control group (p<0.05), respectively. The contents of the globulin in the group of500μg PHE/g were significantly higher than that in the control group; the contents of the albumin in the group of500μg PHE/g were significantly lower than that in the control group (p<0.05); there were no significant differences of the two values in the other two groups with dietary PHE (1000and1500μg PHE/g) compared with the control.2. The activity of alanine aminotransferase increased with the concentration of dietary PHE increasing, but the difference reached significant only between the group of1500μg PHE/g and the control (p<0.05). The activity of aspartate aminotransferase also increased with the concentration of PHE increasing, and the values in the groups at1000and1500μg PHE/g were significantly higher than that in the control group (p<0.05).3. The content of glycogen in hepatopancreas decreased with the dietary PHE increasing, all the differences between the every two tested groups showed significant (p<0.05). The muscle glycogen in the three groups with dietary PHE exposure were significantly lower than that in the control group (p<0.05), but there was no significant difference among them.4. The activity of acetylcholinesterase (TChE) in the brain decreased with the increasing of the dietary PHE level. With the exposure time extension, the activity of TChE in the PHE exposed group was significantly lower than that of the control groups at the7th day and the latter(p<0.05).5. The malonaldehyde (MDA) contents in hepatopancreas, gut and gill increased with the increasing of dietary PHE level. All the differences in guts and gills between the every two tested groups showed significant (p<0.05). In hepatopancreas there was no significant difference betweent500μg PHE/g group and the control, but there were significant differences among the other groups (p<0.05). The MDA contents in hepatopancreas, gut and gill also increased with the exposure time extension. The MDA contents of the hepatopancreas and gut in PHE exposed group were significantly higher than that in the control group at the3rd day and the latter (p<0.05); the MDA content in gill was significantly higher than the control groupat the84th day and the latter (p<0.05).6. With the increasing of dietay PHE level, the total antioxidant capacity (T-AOC) in the hepatopancreas and gut decreased. There was a significant difference in T-AOC level of hepatopancreas between each of the PHE exposed groups and the control group; there was no significant difference in the value between500and1000μg PHE/g group, but those in both groups were significantly higher than that in1500μg PHE/g group (p<0.05), respectively. With extension of the exposure time, T-AOC level in the hepatopancreas in the PHE exposed group showed a "down-up-down" trend, that of gut showed an "up-down" trend, and that of gill showed an increasing trend.7. The activity of glutathione-S-transferase (GST) in the hepatopancreas, gut and gill decreased with dietary PHE level increasing. The GST activity in the hepatopancreas in each of PHE exposed groups were significantly lower than that in the control group (p<0.05). And there were significant differences in the activities of the gut among the different groups (p<0.05). The GST activity of the gill in1500μg PHE/g group was significantly lower than that in each of the other three groups (p<0.05), and there was no significant difference among the other three groups. With the exposure time extension, GST activity in the hepatopancreas of the exposure groups showed a "down-up-down" trend; that in gut showed an "up-down" trend.8. The resting metabolic rate for the standard body weight (MS) increased with the increasing of the dietary PHE level. MS in1500μg PHE/g group was significant higher than that in1000μg PHE/g group (p<0.05), each of them was significantly higher than the control (p<0.05). MS increased with the exposure extension, that in the PHE exposed group was significantly higher than that in the control group at the7th day and the latter (p<0.05).9. The mitochondrial State3respiration rate in the hepatopancreas increased with the increasing of the dietary PHE level. The respiration rates in1000and1500μg PHE/g group were significantly higher than that in the control, and difference was significant between the two groups(p<0.05). With the extension of exposure time, State3respiration rates in the PHE exposed group decreased and it was significantly higher than that of the control group at the56th day and the latter (p<0.05).10. The feed intake and feed efficiency decreased with the increasing of dietary PHE level. There were no significantly differences among the feed intakes in500,1000and1500μg PHE/g groups, but those in each of them was significantly lower than that in the control group (p<0.05); the feed efficiencies among each of the exposure groups was significantly different (p<0.05). With the extension of exposure time, the feed intake and feed efficiency of the PHE exposed group were significantly lower than those in the control group (p<0.05) at the14th and28th days, respectively.11. The organ index increased with the increasing of the dietary PHE level. Hepatopancreas index between500and1000μg PHE/g groups was not significantly different. But those in the two groups were significantly higher than that in the control and lower than that in1500μg PHE/g group (p<0.05). The intestinal index in500μg PHE/g group was not significantly different from the control group, but there were significant difference among the other groups (p<0.05).12. The specific growth rates of body weight (SGR) of the tested fish decreased with the increasing of the dietary PHE level. SGR among the different groups were significantly different (p<0.05). With the exposure time extension, SGRs in the exposure groups were significantly lower than that in the control group at the14th day and the latter(p<0.05).13. The condition factor of fish decreased with the increasing of the dietary PHE level. The condition factor between500and1000μg PHE/g groups were not significantly different (p<0.05), but they were significantly higher than that in1500μg PHE/g group (p<0.05) and also were significantly lower than that in the control (p <0.05)。14. The PHE intake, dietary PHE ration level, PHE accumulation and the ratio of accumulation in the bodies increased with the increasing of the dietary PHE level. All the values among the different groups were different significantly (p<0.05).15. The PHE accumulation in the hepatopancreas, intestine and muscle increased with the increasing of the dietary PHE level. The PHE contents of different organs in the same exposure groups declined in the following order:hepatopancreas> intestine> muscle. The regression relationship of PHE contents in the muscle with the dietary PHE level could be described as:y=0.038x-2.900(r=0.978, p<0.05). The regression relationship of PHE content in the muscle with the exposure time could be described as: y=0.341x+0.791(r2=0.942, p<0.05).The conclusions suggested by the discussion were as follows:1. The fishes from the Zhuyang section of the Yangtze River and those from the Fushun section of the Tuo River are contaminated by PAHs, more serious in the latter.2. The fishes from the Fushun section contained a higher percentage of HMW-PAHs but lower percentages of MMW-PAHs and LMW-PAHs, as compared with those from the Zhuyang section, which may be due to the difference in pollution source of PAHs between the two river sections.3. The hematological index, hepatopancreas index and glycogen content in Spinilbarbus sinensis were influenced by the dietary PHE level. PHE damaged the normal function of the hepatopancreas as well as the carbohydrate metabolism.4. PHE exposure could cause peroxidation damage to the tissues and organs, impairment of detoxification enzyme system, and histological changes in this fish such as enlargement of the hepatopancreas and intestinal tract. All of the toxicological stress would be worse with the increasing of dietary PHE level or extension of PHE exposure time.5. The resting metabolic rate and respiratory rate of mitochondria in the hepatopancreas tissue increased with the increasing of dietary PHE exposure concentration and extension of its exposure time, which suggested that the metabolic rate would increase by physiological adjustment in the fish with dietary PHE exposure to supply extra energy for resisting the toxicological stress. 6. The descend of growth performance (growth rate, feed efficiency, etc.) were accompanied with the metabolism boosting, glycogen contents descend, adjustment of detoxification enzyme activity and so on, which suggested that the lower growth rate in the tested fish was due to insufficiency of its exogenous energy intake and extra cost of the energy for resisting toxico logical stress.7. Under a certain concentration of dietary PHE exposure, the PHE accumulations in various organs of Spinilbarbus sinensis were different, which suggested that PHE accumulation and distribution in this fish should be tissue and organ-specific.8. Based on the national food safety standard in P.R.China, to control the PHE content of the muscle in Spinilbarbus sinensis below the permitted level, the dietary PHE concentration should not be over207.90μg/g when the fish was fed no longer for16weeks, and it should be fed no longer for12days when the dietary PHE is1000μg/g. |
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