| Farmed fish are affected by a lot of different stress factors in actual production. In the present study, we investigated the effects of nitrite exposure and being transported by a jet fish pump on Wuchang bream in order to explore the potential mechanisms of stress responses of fish to different stress factors. Since these processes frequently happen in fish breeding and transportation, this research will help avoiding various risks in aquaculture as well as improving the efficiency of breeding and production. The results showed as follows: 1. Oxidative stress and recovery of gills and livers in Wuchang bream after a subacute exposure to nitriteIn the present study, Fish were exposed to nitrite-free water(control) and various concentrations of nitrite(0.01, 0.3, 1.5, 3 and 15 mg/L) for 14 d. Gills and livers were collected to assay oxidative stress, expression of genes and remodeling of tissue morphology after 14 d of exposure and a 14 d recovery period. The results showed that:(1) Nitrite stress caused doses-time dependent oxidative stress. The major branchial abnormalities in gills were hyperplasia of the primary epithelial cells, edema of secondary epithelium and epithelial lifting. And, the livers presented congestion of hepatic vein, dilation and congestion of hepatic sinusoid, congestion of lobule vein and fuzzy cell outline of hepatocyte.(2) During the nitrite exposure period, the levels of MDA both in gills and livers increased significantly, the activities of Cu/Zn-SOD and CAT in gills showed positive correlation with doses, however, the mRNA levels of Macat and MaCu/Zn sod remained unchanged in gills; It just the activities of Cu/Zn-SOD in the livers showed positive correlation with doses, the activities of CAT and the expression of MaCAT was both suppressed in the livers.(3) During the nitrite exposure period, the GSH significantly decreased in all treatments both in gills and livers, while the activities of GST in gills and livers showed a decreasing tendency, the reason might be that GSH acted as substrate for GPx to eliminate H2O2, not participate in the detoxification process catalyze by GST.(4) During the recovery period, all the pathological lesion and antioxidant indexs both in gills and in livers were alleviated or completely recovery after 14 days, which showed that the effective mechanism of antioxidant defense helped Wuchang bream relieved from shortterm nitrite stress. 2. The response of Wuchang bream to jet fish pumpWe studied the changes of serum COR, GLU, LDH, TC, AST, ALT, CREA of Wuchang bream as well as the respiratory rate at 0, 0.5, 1, 6, 24 h when they passed a jet fish pump at four different operating conditions. In comparison to the control, after transportation fish showed increased serum COR, CREA, LDH, AST and ALT in the initial recovery period, and then decreased to control values gradually within 24 h. However, the contents of serum GLU showed a decline after an initial increase. There was no significant difference in the contents of serum TC in the present study. In addition, the shedding of scales was observed in Wuchang bream under the four the operating conditions. After fish were transported by the jet fish pump, no rupture of swimming bladder and damage of viscera were observed. By compared the results of each operating condition, even though transportation by jet fish pump posed temporary influence on the apparent morphology, respiratory rate and biochemical indexes of Wuchang bream, Wuchang bream returned to normal after 24 h recovery. In conclusion, the influence of jet pump on Wuchang bream was slight and restorable. 3、The response of Grass carp to jet fish pumpWe also do a same experiment to study the response of Grass carp to jet fish pump. In comparison to the control fish, the passed fish under the four operation conditions showed an increase in the values of serum COR, CREA, LDH, AST and ALT at first recovery period and then decreased to control values gradually, while the contents of serum GLU showed a decline after an initial increase. There was no significant difference in the contents of serum TC in the present study. In addition, the descaling was observed in Grass carp under the four the operating conditions. When fish passed the jet fish pump under the four operation conditions there were no rupture of swimming bladder and damage of viscera. By compared the result of each operating condition, the third operating condition influenced lesser than the other operating condition on Grass carp. |
PDF Full Text Request