半咸水、淡水养殖刀鲚消化、抗氧化、非特异性免疫及代谢酶活力的比较分析

Analysis and Comparison of Digestive,Antioxidant,Nonspecific Immunity and Metabolic Enzyme Activities of Coilia nasus Cultured in Brackish Water and Freshwater

为探究刀鲚(Coilia nasus)在半咸水(盐度为8.7~12.5)和淡水养殖条件下消化、抗氧化、非特异性免疫及代谢能力的差异,本研究采用池塘套养方式,以同批次人工繁育的刀鲚1~+龄鱼为研究对象,进行为期210d的养殖实验。结果显示,半咸水养殖刀鲚(以下简称半咸水刀鲚)的生长速度显著大于淡水养殖刀鲚(以下简称淡水刀鲚)(P<0.05),其对蛋白质和淀粉的消化能力均高于淡水刀鲚,而对脂肪的消化有所减弱。其中,半咸水刀鲚的4种内脏器官的淀粉酶(AMS)活力均大于淡水刀鲚,但差异不显著(P>0.05);胃和肝中蛋白酶活力均显著大于淡水刀鲚(P<0.05),肝和盲囊中脂肪酶(LPS)活力均显著低于淡水刀鲚(P<0.05)。半咸水刀鲚的AMS、蛋白酶活力大小顺序均为盲囊>肠>胃>肝,而LPS活力大小顺序为肠>盲囊>胃>肝;淡水刀鲚的AMS、蛋白酶和LPS活力大小顺序均为盲囊>肠>胃>肝。半咸水刀鲚的超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)活力及丙二醛(MDA)含量均显著升高(P<0.05),而过氧化氢酶(CAT)活力显著降低(P<0.05);其肝脏中碱性磷酸酶(AKP)和酸性磷酸酶(ACP)活力均显著低于淡水刀鲚(P<0.05),半咸水对刀鲚谷草转氨酶(AST)活力无显著影响,但会显著降低谷丙转氨酶(ALT)活力。研究表明,半咸水养殖条件不仅促进了刀鲚的生长,提升了刀鲚对蛋白质和淀粉的消化能力,还通过提高SOD和GSH-PX活力来提升刀鲚免疫力,减少外界环境威胁。综上所述,刀鲚更适合在半咸水中进行养殖,建议今后可用半咸水(盐度为8.7~12.5)养殖1~+龄刀鲚。

Coilia nasus is a precious migratory fish typical to the Yangtze River Basin of China.It is locally referred to as the“Three delicious fish of the Yangtze River,”with its fresh meat being particularly delicious and popular.In recent years,wild C.nasus numbers in the Yangtze River Basin have been decreasing due to environmental changes and illegal overfishing,among other reasons.To attenuate the availability of C.nasus,the Shanghai Fisheries Research Institute has successfully established an indoor artificial breeding and pond culture program in 2011.The research and development of C.nasus artificial breeding technologies have steadily progressed,though the artificial breeding yield of C.nasus remains relatively low.In addition,related research on the artificial cultivation of C.nasus is still in its infancy.Research on C.nasus in China and abroad mainly focuses on gonad development,breeding technology,muscle nutrient composition,and growth performance.No reports exist on the effects of brackish water culture conditions on the physiology of C.nasus.Given its economic importance,it would be of great value to evaluate the changes in the digestive,antioxidant,nonspecific immune capacity,and metabolic rates of C.nasus from brackish water(natural seawater in Hangzhou Bay,salinity 8.7~12.5)to freshwater aquaculture,to determine the breeding conditions of C.nasus,and to improve the artificial breeding yield and related technology.To investigate the differences in digestive capacity,antioxidant capacity,nonspecific immune capacity,and metabolic rates of C.nasus in brackish water and freshwater aquaculture conditions,the experiment adopted the pond interbreeding method.Two groups were established:A brackish aquaculture group and a freshwater aquaculture group(control group).Each group was housed in a single aquaculture pond with an area of 0.17 hm^(2).500 C.nasus were stocked in each pond and moved to a Takifugu obscurus pond for a seven-month aquaculture experiment.At the end of the experiment,12 C.nasus were randomly selected from each group and randomly divided into three replicates.Four C.nasus samples were selected from each replicate.The liver,intestine,stomach,and cecum of C.nasus were dissected on an ice plate and carefully removed to prepare a 10%homogenate.The activities of digestive enzymes,antioxidant enzymes,nonspecific immune enzymes,and metabolic enzymes and the total protein content were measured using a kit produced by the Nanjing Jiancheng Bioengineering Institute.The activities of digestive enzymes,antioxidant enzymes,nonspecific immunity enzymes,and metabolic enzymes in brackish water and freshwater aquaculture environments were compared and analyzed in a seven-month aquaculture experiment using the same batch of artificially bred C.nasus.The growth and survival rates of C.nasus cultured in brackish water(hereafter referred to as brackish water C.nasus)were significantly higher than that in the freshwater(hereafter referred to as freshwater C.nasus)(P<0.05).The digestive ability of protein and starch in brackish water C.nasus was higher than that of freshwater C.nasus,while the digestive ability was weakened.Among them,the activity of amylase(AMS)in the four organs of brackish water C.nasus was higher than those in freshwater,but not significantly so(P>0.05).The activities of protease in the liver and stomach were significantly higher than those in freshwater C.nasus(P<0.05),and the activities of lipase(LPS)in the liver and cecum were significantly lower than those in freshwater C.nasus(P<0.05).The order of AMS and protease activity of brackish water C.nasus was:cecum>intestine>stomach>liver,while the order of LPS activity was intestine>cecum>stomach>liver.The order of AMS,protease,and LPS activity of freshwater C.nasus was:cecum>intestine>stomach>liver.Brackish water had significant effects on antioxidant,nonspecific immunity,and metabolic abilities,and the activities of superoxide dismutase(SOD),glutathione peroxidase(GSH-PX),and malondialdehyde(MDA)in the liver of C.nasus were significantly increased,while the activity of catalase(CAT)was significantly decreased(P<0.05).The activities of alkaline phosphatase(AKP)and acid phosphatase(ACP)in the liver of C.nasus in brackish water were significantly lower than those in freshwater(P<0.05).Brackish water had no significant effect on the activity of aspartate aminotransferase(AST),but it significantly reduced the activity of alanine aminotransferase(ALT).In summary,brackish water aquaculture conditions promoted the growth of C.nasus;increased the survival rate;improved the ability of C.nasus to digest protein and starch;improved the immunity of fish;and reduced the influence of external stresses by decreasing the activities of AKP,ACP,and ALT enzymes and increasing the activities of SOD and GSH-PX enzymes.This study also found that C.nasus living in brackish water,as a result of maintaining the internal osmotic balance,significantly reduced ALT enzyme activity and reduced urea production and emission,thereby reducing the pollution of the direct environment.Therefore,brackish water is more suitable for the aquaculture of C.nasus,and it is recommended that brackish water(salinity of 8.7~12.5)be used for aquaculture of 1+age C.nasus individuals in the future.The results of this study provide a scientific basis for the improvement of artificial breeding technology,improving the yield of C.nasus,and the development of special compound feed for C.nasus.