Study On The Early Growth And Antioxidant Capacity Of Polyodon Spathula

In this study,the larvae growth regularity,antioxidant capacity as well as effects of vitamin C on the non-specific immunity,antioxidant capacity and HSP70 gene expression under the nitrous stress in larvae and juvenile Polyodon spathula were explored y using developmental iology,enzymology,and molecular iology research methods.The main results were as follows:1、Study on the growth characteristics of larvae Polyodon spathula。The results showed that:（1）during larval development stage（3¹0d）,the full length、ody weight and age were linearly and exponentially related,the growth equations were:L=0.179t+9.271,R2=0.948;W=0.007e^0.028t,R2=0.889;（2）The equations of ody weight to full length was:W=6.3004 L 2.041,R2=0.814;（3）The specific growth rate of full-length and ody weight were 11.28%and 13.52%at 3⁶ day age,5.51%and 20.80%at 7¹0 day age,respectively.（4）In the organs of head,the width of the mouth and the rostral length were oth allometric growth,the diameter of the eye was isokinetic growth.（5）In the developmental period of juvenile fish,the changes of total length and ody weight with age were exponential and the growth equations were L=8.923e0.061t,R2=0.977 and W=0.003e^0.178t,R²=0.975;（6）The full length with the ody weight equation was:W=5.219x10^-6 L^2.926,R²=0.989;（7）The specific growth rate of full length and ody weight from 12 to 55 day old juveniles were 5.71%and15.99%,respectively.The results indicated that:（1）the growth of the eyes was completed at the age of 3 days after hatching;（2）with respect to full length,the ody weight was presented heterogenic growth in larval stage,while it presented isokinetic growth during juvenile period.2、Changes in antioxidant capacity of juveniles.The results showed that:（1）T-SOD and CAT were present in the larvae during in the endogenous nutrition period（3⁶d）,and the activity increased significantly with the incuation time（P<0.05）.and the maximum value appeared efore the end of the endogenous nutrition period;（2）in the mixed nutrition stage（7¹0d）,the lowest CAT appeared at 7th day age,and then increased;（3）The T-AOC increased gradually at different developmental stages until the yolk sac disappeared,the difference was not significant（P>0.05）,the content of MDA decreased gradually during the development of the larvae while significantly increased eforethe yolk sac disappeared（P<0.05）;（4）T-SOD gradually increased during the development stage of juvenile（12⁵5d）,and the maximum value（19.96+0.05）U/gprot appeared on the 55th day,while the CAT appeared"wave form"variation trend,and the lowest value（1.39+0.10）U/gprot also appeared in the 55th days;（5）During the juvenile stage,the maximum value of T-AOC appeared at the age of 35th day,and then showed a significant downward trend（P<0.05）,and the MDA content appeared to e the minimum at the age of 35th day and then significantly increased（P<0.05）;（6）The overall T-AOC in juvenile stage was higher than that of larval stage;（7）With the development of juvenile fish,alkaline phosphatase and acid phosphatase oth had the maximum value at 35d,and the overall level of alkaline phosphatase activity was higher than acid phosphatase.The results showed that:（1）During the larval development stage,the antioxidant activities of different kinds of antioxidant enzymes were used to enhance antioxidant capacity efore and after feeding;（2）During the juvenile stage,the superoxide dismutase was used to enhance the antioxidant capacity and reduce the oxidative damage.3、Effects of vitamin C on non-specific immunity and antioxidant capacity of juvenile larvae fish under nitrite stress.Preliminary results showed that:（1）During the endogenous nutrition period of larvae,LZM,AKP and ACP increased with the increase of Vc concentration,and the 90mg/L and 120mg/L groups were significantly higher than the control group and the stress group（P<0.05）.In the mixed nutrition period,the LZM,AKP and ACP showed a"rise and fall"phenomenon;（2）From the endogenous nutrition stage to the mixed nutrition stage,in the 90mg/L Vc group,LZM AKP and ACP increased significantly（P<0.05）,and the rising rates were 71.8%51.9%48.4%,respectively;（3）During the larvae stage,T-SOD and T-AOC increased with the increase of Vc concentration,and the 120mg/LVc group was significantly higher than the stress group（P<0.05）,while CAT was significantly higher in the control group than in the stress group and Vc group（P<0.05）,and there was no significant change of CAT with the increase of Vc concentration;（4）The MDA content were decreased with the increase of Vc concentration.compared to the stress group,it was significantly lower in the endogenous and mixed nutrition periods of larvae（P<0.05）.The results indicated that（1）Under the nitrite stress,90mg/L Vc concentration had etter protection on different developmental stages of larvae Polyodon spathula;（2）Nitrite stress could lead to oxidative damage and the imalance of antioxidant capacity in different developmental stages of the larvae.However,Vc could relieve the negative effects of nitrite stress to some extent.4、The influence of Vc on the expression of HSP70 gene under the nitrite stress.The results showed that under nitrite stress,the relative expression of HSP70 in different developmental stages of larvae was significantly higher than that in the control group and Vc group（P<0.05）,ut decreased gradually with the increase of Vc concentration,and restored in the 120mg/LVc group.The results showed that nitrite stress could induce the relative expression of HSP70 in the larvae stage,so as to protect damaged cells or repair damaged cells.120mg/L Vc can reduce the relative expression of HSP70 in stressed larvae,therey enhancing the stress tolerance.