| In order to explore the lethal effect of ammonia stress on tiger &og(Hoplobatrachus chinensis),96h static toxicity test method was adopted to do the acute exposure experiments on the tadpole, juvenile, adult Hoplobatrachus chinensis, and subchronic stress experiment on tiger frog tadpole.96h acute ammonia experiment in 4 ammonia concentrations respectively as 0,120,360 and 600mg/L (concentration 0 was the control group, the other concentrations treatment group) on the adult Hoplobatrachus chinensis to study the toxic effects of different ammonia water on Hoplobatrachus chinensis of different ontogenetic stages, and the effect on tiger frog tadpole growth performance, and the effect on the blood physiological-biochemical indices of the adult Hoplobatrachus chinensis(Glu, MetHb, BUN and BA) and liver tissue antioxidant capacity.The results showed that:the LCso and safety concentration of ammonia on the tadpole、juvenile、adult were respectively 151.15 and 15.11,372.24 and 37.22, 594.62 and 59.46mg/L. Glu reached a maximum value of 2.69 nmol/L after stress for 72h, significantly higher than the other group (P< 0.05), and then returned to the level before stress after 96h. Under ammonia stress, double factors such as concentration and time had significant interactive effects on the content of MetHb and the concentration of BUN (P< 0.05), and the two change showed a rising trend, the content of MetHb was obviously higher than that the control group in 600mg/L and 120mg/L (P< 0.05); the concentration of BUN in 96h for each treatment group was significantly higher than that in 24 and 72h{P< 0.05),but the but the 24,48 and 72h groups had no significant differences (P> 0.05). The change of BA concentration also showed an upward trend, and BA concentrations for each treatment group were significantly higher than that in control group (P< 0.05), but 120,360 and 600mg/L groups had no significant differences (P> 0.05), the BA concentration in 96 and 72h were significantly higher than those in 24 and 48h (P< 0.05), but concentrations between 96 and 72h, and concentrations between 24 and 48h had no significant differences(P> 0.05). Under ammonia stress, double factors such as concentration and time had significant interactive effects on the content of MDA (P< 0.05).The results showed that:the LC50 and safety concentration of ammonia on the tadpole^ juvenile> adult were respectively 151.15 and 15.11,372.24 and 37.22,594.62 and 59.46mg/L. Glu reached a maximum value of 2.69 nmol/L after stress for 72h, significantly higher than the other group (P< 0.05), and then returned to the level before stress after 96h. Under ammonia stress, double factors such as concentration and time had significant interactive effects on the content of MetHb and the concentration of BUN (P< 0.05), and the two change showed a rising trend, the content of MetHb was obviously higher than that the control group in 600mg/L and 120mg/L (P< 0.05); the concentration of BUN in 96h for each treatment group was significantly higher than that in 24 and 72h (P< 0.05),but the but the 24,48 and 72h groups had no significant differences (P> 0.05). The change of BA concentration also showed an upward trend, and BA concentrations for each treatment group were significantly higher than that in control group (P< 0.05), but 120,360 and 600mg/L groups had no significant differences (P> 0.05), the BA concentration in 96 and 72h were significantly higher than those in 24 and 48h (P< 0.05), but concentrations between 96 and 72h, and concentrations between 24 and 48h had no significant differences(P> 0.05). Under ammonia stress, double factors such as concentration and time had significant interactive effects on the content of MDA {P< 0.05). And at different times and different concentrations MDA content had significant difference after ammonia nitrogen stress. MDA content changed to rise as a whole in adult tiger forg. In each time group of 24,48,72 and 96 h, MDA content had no significant difference (P> 0.05) between 0 mg/L (control group) and 120 mg/L. And MDA content significantly increased (P< 0.05) in 360 mg/L and 600 mg/L. In various concentrations group,0 mg/L (control group) and 120 mg/L MDA content there was no significant difference (P> 0.05) in 0,24,48,72 and 96 h. MDA content of 360 mg/L and 600 mg/L increased in 24 h. MDA content decreased in 24-48 h, but still significantly higher than the control group and 120 mg/L (P< 0.05). On the contrary, MDA content increased in 48-96 h. Double factors such as concentration and time had significant interactive effects on the content of T-AOC (P< 0.05). And at different times and different concentrations T-AOC content had significant difference after ammonia nitrogen stress. T-AOC changed to decline as a whole. In each time group,120 mg/L T-AOC was significantly higher than 0 mg/L (control group) (P< 0.05). And the T-AOC in 360, 600 mg/L had no significant difference (P> 0.05) with control group in 24 h.120, 360 and 600 mg/L T-AOC were significantly lower than the control group (P< 0.05) in 48 h. The T-AOC in 120,360 and 600 mg/L groups had no significant differences (P> 0.05) between each other. After stress for 72 h and 96 h the T-AOC in 120,360 and 600 mg/L were all significantly lower than the control group (P< 0.05). The T-AOC in 120 and 360 mg/L had no significant difference (P> 0.05), and higher than that in 600 mg/L group. In various concentrations group, in 120 mg/L, the T-AOC rised at first and then fell with extend the exposure time. The T-AOC in 24 h was higher than the control group (P< 0.05). And T-AOC in 48,72 and 96 h was significantly lower than control group (P< 0.05). The T-AOC in 48 h was higher than those in 72 h and 96 h. And the T-AOC in 72 h and 96 h group had no significant difference (P> 0.05). The T-AOC in different time group of 360 mg/L and 120 mg/L had same change trend. With the extension of exposure time the T-AOC in 600 mg/L gradually declined.Experiments showed that Hoplobatrachus chinensis of different ontogenetic stages had different sensitivities on ammonia and along with its growth and development, its tolerance on ammonia gradually increased, and its sensitivity decreased. During the early stage of stress, adult Hoplobatrachus chinensis enhanced its stress effect. As the stress time prolonged, the frog body adaptive physiological regulation, but its respiration and excretion system underwent severe disturbances, and kidney tissue appeared lesions. It could be seen ammonia stress significantly affected the physiological effects of Hoplobatrachus chinensis. Therefore in the cultivation process the water ammonia concentration should be timely monitored to prevent diseases. |
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