Effect of seawater strontium concentration on enzymes involved in metabolism and immunity of Liza haematocheila during otolith strontium marking
In the process of otolith strontium marking of Liza haematocheila,it is necessary to add strontium to the growing environment,which may affect the metabolism and immunity of L.haematocheila.In order to explore the effect of seawater strontium concentration on enzymes involved in metabolism and immunity of L.haematocheila during strontium marking on otolith,two marking treatments(S1 and S2)and one control treatment(C0)were designed.In C0,L.haematocheila were raised in normal seawater,the Sr2+concentration was 7.9 mg·L-1.The seawater used in treatment S1 and S2 were normal seawater with SrCl2·6H2O added,and the mass concentration of Sr2+in seawater was 50 mg·L-1 and 200 mg·L-1,respectively.A total of 330 healthy juveniles with a body length of(3.00±0.26)cm were selected and evenly distributed to treatments CO,S1 and S2.During the strontium marking period,each treatment were consisted of 11 cuboid glass aquariums containing 30 L water,and 10 juveniles were placed in each aquarium.After 96 h of strontium marking,the remaining juveniles in each treatment were separately transferred to an aquarium with natural sea water and continued to be cultured until the end of the experiment.At 0.5,1,3,6,9,12,24,48,72,96 h of marking experiment and 24 h after marking experiment(120 h),five fish were sampled and prepared for further analysis.Pyruvate kinase(PK)and lactate dehydrogenase(LDH)were used as metabolism indicators,and superoxide dismutases(SOD)and nitric oxide synthase(NOS)were used as immunity indicators.The results were as follows:1)In seawater with 50 mg·L-1 of Sr2+,there was no significant effect on the metabolism-related enzyme indexes(PK and LDH)and immune-related enzyme indexes(SOD and NOS)of L.haematocheila.2)In seawater with 200 mg·L-1 of Sr2+,PK activities increased first,then decreased to a relatively stable level,which was different from that of the control.And PK activities of L.haematocheila at 1,3,6,9 h were significantly higher than those of CO and S1 treatments.The mean PK values of the whole experiment period were significantly higher than those of the control.3)In seawater with 200 mg·L-1 of Sr2+,the changes of LDH,SOD and NOS of L.haematocheila were similar to those of the control,and the mean values of the above three indicators were not significantly different from those of the control at each stage of the experiment.These results showed that seawater with 50 mg·L-1 Sr2+had no significant effect on the energy metabolism and immune function of L.haematocheila,while seawater with 200 mg·L-1 Sr2+only increased the energy demand of L.haematocheila in the early stage of marking to resist the high strontium pressure.However,this pressure did not cause hypoxia and did not affect immune function of L.haematocheila.Therefore,we suggest that increasing the supply and other nutrients of food for L.haematocheila during the beginning of otolith strontium marking should be appropriate,and other breeding management measures should be consistent with the normal.
Liza haematocheilaotolith strontium markingenzymes involved in metabolismenzymes involved in immunity
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