The Physiological Responses To Ammonia Stress And Vitamin C Requirement Of Juvenile Black Seabream (Acanthopagrus Schlegeli)

1 The acute toxicity of ammonia on larval and juvenile black seabream,Acanthopagrus schlegeliA study was designed to investigate the toxicity of ammonia on larva(weght 1.0±0.2g)and juvenile(30.0±2.0g)black seabrea,Acanthopagrus schlegeli,the expriment was carried out at water temperature 25℃,salinity 28 and pH8.1.The ammonia concentration adjusted with NH₄Cl.The lavera fish were submitted to 0, 20.0 mg/L,26.0 mg/L,33.8 mg/L,43.94 mg/L and 57.12 mg/L,giving six different ammonia-N concentrations.The juvenile fish were submitted to 0,30.0 mg/L,34.5 mg/L,39.7 mg/L,45.6 mg/L,52.5 mg/L.The result showed that the 24hLC₅₀,48hLC₅₀,72hLC₅₀,96hLC₅₀of the young fish was 2.43mg/L,2.09mg/L,1.90mg/L,1.74mg NH3-N/L,respectively,the safety concentrations was 0.174mg/L NH3-N. The 24hLC₅₀,48hLC₅₀,72hLC₅₀,96hLC₅₀of juvenile fish was 3.10mg/L,2.47mg/L,2.15mg/L,1.99mg NH₃-N/L,respectively.The safety concentrations was 0.199mg NH₃-N/L.2 The effect of ammonia stress on serum cortisol,glucose and lactate of juvenile black seabream,Acanthopagrus schlegeliA short-term acute ammonia was carried out to investigate the effect on serum cortisol,glucose and lactate of juvenile black seabream,Acanthopagrus schlegeli with three ammonia concentration(0,10,20mg TAN/L,equal to 0,0.67,1.33mg NH₃-N) under water temperture 25℃.The fish was sampled serum at 0h,6h,12h,24h,48h, 96h.The results showed that,no significant changes in the coritsol level of control group was found,but the 10mg TAN/L and 20mgTAN/L group got to the highest and were 65.07ng/ml and 70.97ng/ml respectively,which both were significantly higher than that of control group(P＜0.05).Then the cortisol level of all treatment groups started to decrease which got back to the normal level at 96h.The change of serum glucose and lactate content were similar to cortisol,which also fisrtly increased and then decreaseed.This study indicated that there was a siginificantly stress of black seabream to acute ammonia stress and the fish can adapt to the stress if the ammonia concentration was not too high.3 Effect of ammonia stress on growth of black seabream, Acanthopagrus schlegeli under different salinitiesThe effect of different ammonia-N(0,5,10mg/ml)on the growth of black seabream,were investigate under three different salinities 20,28,36.The result showed that under the different salinities,the weight growth ratio(WGR)and specific growth ratio(SGR)of juvenile black seabream decreased with the increase of the ammonia-N concentrations,while the feed conversion ratio(FCR)was increased with the ammonia-N concetration.Under the salinities of 20,there were significantly difference between the highest ammonia concentration group and the lowest ammonia group(P＜0.05),while undere salinity 28 and salinity 36,there was no singificant difference in WGR and SGR of three ammonia concentration groups,the highest FCR was 2.82,which appeared in 10mg N/L at salinity 36.The lowest was 2.12,which appeared in 0mg N/L at salinity 20.Besides,there was no significant difference of body compsition in all treatment groups.4 Effect of ammonia stress on the activity of SOD and CAT in black seabream,Acanthopagrus schlegeli under different salinitiesThe effect of different ammonia-N(0,5,10mgTAN/ml,equal to 0,0.33,0.67mg NH₃-N/L)on the activity of superoxied dismutase(SOD)and catalase(CAT)of juvenile black seabream,Acanthopagrus schlegeli were investigated under different salinities.The water temperature was 25℃,and pH was 8.1.The black seabream, Acanthopagrus schlegel were exposed to ammonia-N for a period of 30d and sampled at 0,6,12,18,24,30d and evaluted the effect of ammonia-N exposure on the activity of SOD and CAT of black seabream,Acanthopagrus schlegeli.The results showed that,the SOD activity of 10mgTAN/ml group was firstly increased and then deceased with the increasing of ammonia exposure time at salinity 20 and salinity 28. The SOD and CAT activity of all ammonia treatment groups were got back to the level of that before exposure.There were no significant difference at different salinity and ammonia treatment group.The CAT activity trend was similar to SOD.The CAT activity of 5mg/L and 10mgTAN/L group was firstly increased and then deceased as to ammonia exposure time at salinity 20 and salinity 28.The possible was 5mg/L and 10mgTAN/ml can promoted the synthesize of SOD and CAT at salinity 20 and salinity 28,but the ammonia cann't rosed juvenile hyperirritability.When the fish adapt to the ammonia stress,all enzyme got back to normal.5 Effect of dietary vitmain C on growth and immune response in black seabream,Acanthopagrus schlegeliA feeding experiment was conducted to investigate the effect of dietary vitamin C on growth and immune function in black seabream,Acanthopagrus schlegeli,with the fish meal and casin as the protein sourse,seven experiment diets supplemented at 0,50,100,200,400,800,1600mg/kg vitamin C,respectively,were fed to black seabream,Acanthopagrus schlegeli(mean weight 10.54±1.2g)for 8 weeks.Each diet was feed to three replicate groups of black seabream.The results showed that,after 8 weeks,there were significant difference in weight gain rate(WGR)and feed conversion ratio(FCR)between the groups(P＜0.05).The WGR was highest and the FCR was lowest in group of 200mg/kg,while the group of control had the lowest WGR and SGR.The concent of vitamin C in the liver was signifecently affected by dietary vitamin C(P＜0.05).The activity of superoxide dismutase(SOD)and catalase (CAT)in liver increased with the level of dietary vitamin C,but there were no significant difference was found among the treatments.Based on these results,the adequate dietary vitamin C for juvenile black seabream,Acanthopagrus schlegeli estimated by growth data is about 200 mg/kg...