Abstract:Ten microsatellite loci were selected to analyze the correlation with quantitative trait locus of body weight and length genomic of Apostichopus japonicus using single marker-based analysis.DNA of 60 eight months old individuals of Apostichopus japonicus which have differences in growth traits were analyzed by 10 microsatellite markers.The results showed that a total of 50 different alleles were found,the number of alleles in each locus was 3 to 7,and the number of mean valid alleles was 5.0.The polymorphism information content(PIC)of ten microsatellite loci was 0.083 3 to 0.666 7,and the value of heterozygosity was 0.236 1 to 0.767 7,which proved the ten loci can be adopted to make correlation analysis.SPSS program was used to analyze the effects of these 10 microsatellites on body weight and length of Apostichopus japonicus.The results showed that AB,AD and CD genotypes of AjSSR02 had significant difference in body weight and length with other types,allele A of AjSSR04 played a positive role in both body weight and length,FF genotype of AjSSR06 had a significant impact on weight but not on length,and A and B allele of AjSSR09 played positive and negative roles in growth traits respectively.

Abstract:The growth of the lymphoid organs,such as head kidney,spleen and thymus was stueied in Larimichthys crocea,from hatching to 12 months of age.A histological and ultrastructural study was performed on the development of the head kidney,thymus and spleen aging from just hatching to the 12 months.Head kidney was first present on the 3^rd day after hatching(DAH).Primordial haemopoietic stem cells were first observed in the head kidney and rapidly differentiated into different cellular types.Progenitor spleen was present on the 4^th DAH,located close to the gut,soon becoming rich in blood capillaries,red blood cells and thrombocytes.The thymus occurred obviously on the 4^th DAH,located on either side of the upper corner of the opercular cavity,closely under the membrance of the opercuhr cavity.The thymus was the last lymphoid organ appearing but showed quick development.The thymus consisted of outer thymocytic and inner epithelioid zones.There was no obvious demarcation between them,but both zones were visible.Head kidney,spleen and thymus grew as the fish grew.The spleen weight showed a closer correlation to body weight than they did to age.But head kidney and thymus weight showed a closer correlation to age.The total number of leucocytes in the lymphoid organs increased with age.But the number per milligram of lymphoid organ didn’t show a closer correlation to age.The head kidney was more lymphoid than the spleen.The blood components had no obvious ralationship with age or season during the period studied.

Abstract:According to the formulas of effective population size,which were brought forward by Doyle and Talbot,we estimated the effective population size(N_e)for rapid growth line fundamental stock in Portunus trituberculatus.The real N_e was 213,which corresponded to a rate of inbreeding(F)of 0.23%.Results indicated that F is relatively small,and inbreeding depression was in a low level,however,the cost of conservation was too high,it did not meet the conservation requirements.In light of breed conservation model in livestock and poultry,we investigated rapid growth line fundamental stock in P.trituberculatus on methods of selecting parents and ratio of dams and sires and the size of conservation population.We made the rules as follows:random selecting parents,the ratio of dams and sires is 1∶1,and the number of dams and sires is 131,respectively.In this situation,genetic diversity of rapid growth line fundamental stock is preferably rich,which satisfies selective breeding,at the same time the cost of breed conservation is economical.This is only a theoretical model of breed conservation,and it needs the process of gradual improvement of breeding populations in the future.

Abstract:Teleost fish have a unique physical barrier composed of mucus and skin which act as the first line of defence.It has been shown that lymphocytes are present in the epidermis of fish,and the cutaneous mucus of several fish species contains immunoglobulin(Ig).As fish mucosal composition was complicated and the content of Ig was low,it is difficult to obtain high purity mucus Ig.In this study,skin mucus Ig of Japanese flounder(Paralichthys olivaceus)was purified by the combination of saturated ammonium sulfate precipitation,Sephacryl S300 gel filtration chromatography and DEAE Sepharose chromatography,and partial characteristics of purified proteins were analyzed by SDS-PAGE and Western-blot.According to SDSPAGE,many other proteins were removed from mucus by precipitation of 30% and 50% saturated ammonium sulfate solution,and Ig that was crudely extracted could reach a high purity by further purification using Sephacryl S300.After being finally purified by DEAE Sepharose chromatography,skin mucus Ig has only two bands of 72 and 26 ku,initially presumed as the heavy chain and light chain of Japanese flounder mucus Ig.Western-blot analysis showed that the monoclonal antibody produced from serum Ig could recognize the heavy chain of mucus Ig(72 ku).

Abstract:Salinity is an important ecological factor in the algal growth.Water loss would lead to the increase of salinity in mass culture of fish food diatom,which could affect the algal photosynthesis and inorganic carbon utilization.In this paper,impacts of salinity on the growth,carbonic anhydrase activity,photosynthesis(P-I curve)and chlorophyll a fluorescence parameters in Nitzschia closterium f. minutissima were investigated to explore the photosynthetic mechanism of the diatom under the high salinity.The results showed that the specific growth rate when Nitzschia closterium f. minutissima was grown in high salinity(70)was decreased by 59.2% compared with the normal seawater,but it can maintain the growth to a certain degree in salinity up to 60-70,which suggested that Nitzschia closterium f. minutissima had a stronger tolerance to high salinity.The extracellular carbonic anhydrase activity which was measured by an electrometric method was reduced by 66.3%,and Chl.a and Chl.c contents which was determined spectrophotometrically were also decreased by 50.0% and 45.7% in high salinity(70).The extracellular CA activity was inhibited in high salinity environment which showed that capacity of HCO^-₃ catalyzed by extracellular CA into CO₂ declined,and high salinity stress can damage the Chl.a/b light harvesting complex(LHCII)and reaction-center complex and affect pigment synthesis.The chlorophyll a fluorescence parameters were measured by saturation pulse,and the maximal efficiency of PSⅡ photochemistry(F_v/F_m),actual photochemical efficiency of PSⅡ(Yield),photochemical quenching co-efficient(qP)decreased,whereas nonphotochemical quenching co-efficient(qN)increased when the algae were grown in high salinity.These results showed that the high salinity stress would damage the PSⅡ reaction center,inhibit primary reaction of photosynthesis as well as the process of photosynthetic electron transport.The photosynthetic rate in the varied light intensity and inorganic carbon concentration was determined with a Clark-type oxygen electrode,and maximal photosynthetic rate(P_max),photosynthetic efficiency(α)and the affinity for inorganic carbon(K_0.5)obtained by non-linear fitting from P-I and P-C curves also declined in high salinity.All the above results suggested that the growth and photosynthesis in Nitzschia closterium f.minutissima could be partially inhibited by higher salinity,but it also could adapt to high salinity stress through adjusting the activity of extracellular carbonic anhydrase,the affinity for inorganic carbon and photosystem Ⅱ energy flow and energy utilization efficiency.

Abstract:Since promulgation on April 15,2005,“Administration Measures of Shanghai Yangtze Estuarine Nature Reserve for Chinese Sturgeon”provides a powerful means of legal protection for an effective protection of Chinese sturgeon(Acipenser sinensis)and their natural ecological environment.However,due to regulations,adopting the principle of broad rather than detailed in the form of technical and specific legislative provisions on the law and a number of issues dealing with the fuzzy form,so many provisions can not meet the actual needs of the protection.In 2009,local laws and regulations legislation on the nature reserve was included in the legislative plan by Municipal People’s Congress.In this context,this article analyzes the legal system problems on the nature reserve,discusses the source of the problem,describes the feasibility of local laws and regulations legislation on the nature reserve.Firstly,there is a solid legal foundation.Secondly,local regulations will be up to the local laws and regulations after being implemented for some time which is in line with our legislative practice in China.Thirdly,local laws and regulations issued is the only viable way to solve the problems in the “Measures”.Some suggestions have been put forward on local laws and regulations legislation on the nature reserve.First,four goals of the legislation should be established.Second,we should adhere to two principles of the legislation.One is basic principles,which include the principles of sustainable development,precautionary principle,the principle of ecological priority,systemic protection principles.The other is the specific principles of local laws and regulations legislation,Including the local principle and the principle of creation.Last,six basic systems should be established,such as open management,characteristics of biological resources,land properties,ecological compensation,public participation,special ambulance with the domestication and breeding.

Abstract:The effects of two lectins from Undaria pinnatifida and Scytosiphon lomentarius on the activities of acid phosphatase(ACP),alkaline phosphatase(AKP),lysozyme(LSZ)and catalase(CAT)of A.japonicus were studied by supplying various Undaria pinnatifida-lectin or S.lomentariuslectin levels in diets.The experimental dietary levels of U.pinnatifida lectin were 0.58%(m/m),1.16% and 2.32%,and those of S.lomentarius lectin were 0.32%,0.64% and 1.28%,respectively.Group fed with basic feed was set as control.On the 4th,8th,13th and 17th day after feeding,the activities of ACP,AKP,LSZ and CAT in A.japonicus were determined.The results indicated that the activity of ACP sustainably increased and was higher than the control among 17 days.The activities of LSZ increased firstly after lectins feeding except S.lomentarius lectin on 17th day,which decreased on this day,and the activities of LSZ were proportionally related to the additional dosage of two kinds of lectins.The CAT activity of U.pinnatifida lectin groups increased as the time went on,however CAT activity,firstly increased and then decreased in S.lomentarius lectin groups.

Abstract:This paper introduces nutritional value of corn gluten meal(CGM),and reviews the effects of CGM on growth performance,palatability,apparent digestibility and balance of amino acids of the CGM or the feeds,body biochemical index,muscle composition and aquatic environment when the aquatic animals were fed with the diets containing CGM.The ways to improve the utilization of CGM by aquatic animals are also discussed.It should be further researched focusing on metabolism of CGM in different aquatic animals,effect of the replacement of fish meal by CGM on disease resistance,immunity and meat flavor.With rising raw material prices,the replacement of other animal proteins execpt fish meal by CGM will be of significance.

Abstract:The molecular weights,chemical compositions and scavenging activities on oxygen free radicals of various sulfated polysaccharides and alginate from Laminaria japonica were compared to make clear the structureactivity relationship and mechanism of antioxidant activities of polysaccharides on oxygen free radicals.The results showed that low sulfated fraction F-A2,with a peakmolecular weight(Mp)of 6-15 ku exhibited a very strong antioxidant activity on superoxide and hydroxyl radicals,however,the highly sulfated fractions with Mp below 15 ku had vere low antioxidant activity.The low molecular weight alginate especially fraction with molecular weight below 1 ku obtained by enzymatic hydrolysis had higher scavenging activity than sulfated polysaccharides from L.japonica.These results indicated sulfate group of low molecular weight sulfated polysaccharide seems a dimensional block for the reaction with oxygen radicals,while glucuronic acid content contributes much to the scavenging activities of polysaccharides on oxygen free radicals.The chemical properties and scavenging activities of sulfated polysaccharide fractions Fa1(Mp 8 ku)and Fa2(1 ku)obtained by hydroxyl radical process degradation of crude sulfated polysaccharide showed that hydroxyl radical process mainly degraded the ascopyllan-like species rich in glucuronic acid,mannose and glucose,while fraction rich in sulfated L-fucose remained unchanged.These results suggest that antioxidant activity of sulfated polysaccharides is apparently related not only to molecular weight and sulfated ester content,as previously determined,but also to the glucuronic acid,fucose contents and neutral sugars in polysaccharides chain.

Abstract:The present situation and existing problems of the aquatic products processing industry,mainly including scientific and technical-level,production equipments,high value-added products,deep processing of aquatic products,industrial structure,quality standard system of aquatic products,laws and regulations,are reviewed in this paper.The main factors affecting the aquatic products processing industry towards a low-carbon economy are discussed in detail.The measures and ideas about how to develop low-carbon economy in the aquatic products processing industry are proposed,which rely on technological innovation,improvement of comprehensive application of industrial by-products and refined-processing technologies of aquatic products,strengthening policy guidance,and adjustment of industry structure.

Abstract:The aluminum content in seaweed was first researched in out country.The results showed that the aluminum content ranged from 53.2 mg/kg to 2 714.6 mg/kg,especially for laver which had highest average value.The speciation analysis of aluminum was first conducted in seaweed using sequential chemical extraction.There were several forms of aluminum in seaweed and the main speciation was organic aluminum which was stable and not easy to be absorbed by organism.It accounted for 82.5%-87.6% of the total aluminum.The inorganic aluminum which had higher toxicity accounted for only 3.75%-4.94% of the total amount.The present research further proved that it was not enough to use total aluminum as the standard to evaluate the safety of the seaweed,and it was urgent to establish different limitation standards according to different aluminum speciation in order to accurately evaluate the safety of the seaweed and guarantee the healthy development of the seaweed industry.

Abstract:In this study,effects on physiological and biochemical indexes of gametophytic blades of an low nitrogen and phosphorus tolerance line(9-Ⅳ) of Porphyra haitanensis under low nitrogen and phosphorus stress were observed.They were grown in medium with low content of nitrogen and phosphorus for 0,2,4,6,8 and 10 days.Changes in three quality indexes were measured,including the contents of pigment,crude protein and free amino acids.Results showed that all the three quality indexes of P.haitanensis were significantly declined under low nitrogen and phosphorus stress.Furthermore,changes in physiology also were measured,including free radical content,H₂O₂,malondialdehyde(MDA)and proline levels,and the activities of superoxide dismutase,peroxidase,and catalase.These physiological indexes were all presented as dynamic changes in the stress days.Based on these data,the physiological changes within the 9-Ⅳ blades were as follows:low nitrogen and phosphorus stress→cell membranes were damaged by oxidation and MDA levels increased→cells received signals of excessive ROS→antioxidation and osmoregulation systems began to clean out excessive ROS→free radical levels declined.Our results laid a foundation for understanding the principle of low nitrogen and phosphorus tolerance in P.haitanensis,and provided some directions for future breeding.

Abstract:Monostroma latissimum is one edible Chlorophyta species,and is a potential new species for economic seaweed cultivation by fishermen in China,for viable protoplasts could be potentially used as a source for seed material of macrophytic marine algae cultivation and for other applied phycological research,so the aim of this study was to develop a new breeding method by culturing the protoplasts of M.latissimum,to form seedlings quickly,to shorten the traditional period of germlings cultivation,to maintain a stock of seedlings in the laboratory for longer periods,and to provide abundant germlings for largescale commercial cultivation.Protoplasts were isolated respectively from different parts of the thalli of M.latissimumwhich are collected at different time by enzymatic method(optimal enzyme composition consisted of 4% pectinase and 2% cellulase).And the regeneration,differentiation and development pathway of different derived protoplasts are studied under uniform conditions of isolation and incubation.According to the cell morphology,such as the formation of rhizoids,whether having hyaline sheath,or the size and arrangement ways of the cell,and the eventual development and differentiation trend,the protoplast development can be divided into eight results,include forming somatic cells and reproductive cells.The somatic cells formation can be classified into cell mass which includes regular or irregular cell mass; abnormal seedlings which include rhizoidal,rhizoidallike,no rhizoidal and tubular abnormal seedlings; normal seedlings,3 types,7 results.The reproductive cells formation developed into gametangia firstly,and then developed into sporangia.Each development pathway is associated with age,size and location of algae.This is the first time to report that some protoplasts underwent repeated cell divisions and developed directly into thalli similar to the parent thalli,and the application and expectations of protoplast culture were also discussed.

Abstract:It is important to master the knowledge of the ovary development of skipjack,to provide a fundamental information for further study on reproduction mechanism,spawning date and times,batch fecundity,body size of first sex maturation etc.This is also the basic data for the skipjack biological study and resource assessment.140 ovaries of skipjack(Katsuwonus pelamis)have been studied by means of histological method,and the samples were collected from the EEZs of Papua New Guinea and Federal States of Micronesia in the Western and Central Pacific(WCPO)during October 2007 to January 2008 on board purse seine vessels.Samples for histological study were fixed in formalin solution and processed by the standard methods.Sections(thickness 7 μm)were stained by hematoxylin-eosin.In the course of studying ovogenesis,we observed ovary features through Olympus BX-51 microscope camera and determined ovarian development stages.Full stages of maturity and cells progress have been observed and described in detail in this paper reflecting the ovogenesis development.The main results are:(a) Mature development of oocyte can be marked as six periods.According to that,six phases are outlined for ovary.At the first stage,the cell is small and the ratio of nucleolus to cytoplasm is big.At the second stage,a follicular cells layer is around the nucleolus,cytoplasm becomes two layers,there are some small fat drops around the nucleolus.At the third stage,yolk granules occur and increase gradually.At the fourth stage,the cell volume grows bigger while fat drops fuse and yolk granules fuse.At the fifth stage,fertilization hole pouches and ovulation is happening.And at the sixth stage,nucleolus blurs and cytoplasm decreases.(b) Skipjack is a type of multiple spawning species,varied oocyte phases can be observed in one ovary at the same time.GSI changes obviously when ovary develops from stage Ⅲ to Ⅳ and from Ⅴ to Ⅵ,but there exists much overlap from Ⅰ to Ⅵ period.(c) Traditional gonad identification system shows obviou inaccuracy for skipjack tuna and for the gonad in Ⅵ period especially.For stagefigonad,identification by traditional system are almost consistent with histological system.The higher stages of ovarian development,the greater error between the two methods.When gonad is in stage Ⅰ,gender cannot be identifed by naked eye,so comparison only be made from Ⅱ to Ⅳ.(d) For average GSI of each day from Oct.22th 2007 to Jan.2nd 2008,there are two peaks during late November(early December),the lowest point of close to 2,up to 10,generally more than 4.Late December,GSI decreased between 0 and 2.The end of December(early January),another peak occurred,and gradually more than 3,and up to 4 or more,close to 6.Two peaks of spawning period have been identified during the surveys,and they are from the end of November to the early December,and from the end of December to the early January.

Abstract:The reproductive system and gonad development and germ cell occur rence of Hemifusus tuba have been studied by using tissue section techniques.Through tissue section observation,the results showed that H.tuba is gonochorism,and the male reproductive system is mainly composed of spermary,seminal vesicle,prostate,deferent duct and the penis.The structure of the spermary is more branches tubular gland,is composed of the seminiferous tubules and ductulus efferens.According to the size,shape and distribution features of the cell,this paper analysed the form of spermatogenesis which experienced a fivestage process,from spermatogonia,primary spermatocytes,secondary spermatocytes,sperm cells to sperms.According to the topography of the genital cells in the seminiferous tubules and the quantity of the intestitial cell,the development will be divided into the testes of degradtion period,developing period(spermatocytes separatist period),maturation and mature period,degradtion period,in all four periods.The structure type of the ovary was follicular and it consists of follicle and genital ducts,was full of eosinophilic granule.The ovary development can be divided into following five periods:proliferation period,growth period,maturation period,spawning period and resting period.By the germ cells’ size,shape and the amount of yolk granules inside,the oogenesis H.tuba might be divided into proliferation period,growth period and maturation period.Gonad and germ cell developments of H.tuba are not synchronized,for they were repeatedly sexually mature,repeatedly ranked fine way.

Abstract:The numbers and composition of bacterial communities in bio-filters of re-circulating mariculture system were studied.The numbers of total heterotrophic bacteria,ammonium-oxidizing bacteria and nitrateoxidizing bacteria on the matured bio-film samples from the 4 bio-filters with different initial ammonianitrogen concentrations(1#,2#,3#,4#)and from the water sample(5#)of 3# bio-filter were counted.The results showed that,the numbers of ammonia-oxidizing bacteria and nitrate-oxidizing bacteria on the bio-films increased and the number of heterotrophic bacteria declined gradually with the increase of initial ammonia-nitrogen concentrations in bio-filters.The numbers of bacteria on bio-film were higher by 3-4 orders of magnitude than those of the water sample in the same bio-filter.The amplifying products of the fragments of 16S rRNA gene from above samples were analyzed with denaturing gradient electrophoresis(DGGE),and the sequences of DGGE bands were phylogenetic analyzed.The abundant bacterial diversity was found in bio-filtors of re-circulating systems,and higher on biofilm than in water in the same bio-filtor.The bacteria communities in bio-film and water samples were mainly made up with two bacterial groups:Flavobacteria,and α-,β-,γ-Proteobacteria,including 15 genera.The predominant bacteria on bio-films were Olleya,Lacinutrix,Gaetbulibacter,Sediminibacter,Leisingera,Psychroserpens and Nitrosomonas.While those of water were significantly different,including Vitellibacter,Nautella,Roseobacter,and a sulfur-oxidizing bacterium.Nitrosomonas became predominant bacteria on bio-films gradually with the increase of initial ammonia-nitrogen concentrations.The results suggested that,during the maturation of bio-film,increasing the initial ammonia-nitrogen concentrations is beneficial to the gathering of nitrifying bacteria and the improvement of nitrogen removing efficiency.

Abstract:A 2 804 bp full-length cDNA sequence of catalase(CAT)gene from Hypriopsis cumingii was obtained by rapid amplification of cDNA ends.It consists of a 112 bp 5′UTR(untranslated region),a 1 388 bp ORF(open reading frame)and a 1 303 bp 3′UTR,and the deduced protein is composed of 462 amino acids,with calculated molecular weight of 52.7 ku,and its isoelectric point was 6.35.Motif analysis showed that CAT deduced amino acid sequence contained a highly conserved catalytic site motif “23FDRERIPERVVHAKGAG39”.Twelve amino acids(Asp107,His153,Phe157,Ser160,Arg162,Asn172,Try174,Lys196,Val261,Trp262,His264 and Try317)of CAT gene of H.cumingii were identified as putative residues involved in NADPH binding,and they were different in different species.The CAT amino acid residues of H.cumingii shared a high similarity with other molluscs(99%),and shrimp,fish,amphibians,mammals(98%-99%).The obtained CAT of H.cumingii was predicted as CAT3.NJ tree suggested that H.cumingii clustered with mollusca firstly,and then clustered with shrimp,fish,amphibians and mammals.Real-time quantitative RT-PCR results displayed that CAT gene was expressed in a wide range of seven organs,with the lowest level of transcripts found in kidney.Its expression was upregulated in blood,which was significantly different from other organs.The expressions of other five organs were generally upregulated first and then downregulated.

Abstract:The content of moisture,crude protein,crude fat,ash,glycosaminoglycans,saponin,the composition of fatty acids and amino acids and 16 kinds of elements were comparatively analyzed in body wall and internal organs of sea cucumber Apostichopus japonicus collected at Rushan.The results showed that the contents of moisture,crude protein,crude fat,ash,glycosaminoglycans and saponin averaged 90.67%,76.11%;49.75%,34.90%;6.56%,5.15%;27.50%,36.85%;7.47%,1.08%;0.062 2%,0.017 4%;respectively.21 kinds of fatty acids were found in both body wall and internal organs.Internal organs have more PUFAs,the EPA and DHA were the predominate fatty acids,accounting for 13.09% and 6.88%.Thirteen kinds of amino acids were detected in both body wall and internal organs,including 8 kinds of essential amino acids which accounted for 39.36%,39.93% of total amino acids.The two parts were both rich in flavor amino acids［19.07,11.57 g/(100 g)］such as glutamic acid(Glu),aspartic acid(Asp)and efficacy amino acids［10.78,7.06 g/(100 g)］such as argine acid(Arg).The AAS and CS of the essential amino acids of the internal organs were lower than those of body wall.Both parts are rich in minerals,especially elements Mg,Fe,Zn,V,Se.The contents of V and Mn in the internal organs are particularly rich.The internal organs of sea cucumber A.japonicus are the potential material for diet and medicine,which should be fully utilized.

Abstract:The complete mitochondrial genome of the Onchidium struma is important for general molecular and evolutionary studies in Onchidiidae.Via long and accurate polymerase chain reaction(LA-PCR),a complete mitochondrial genome sequence of the O.struma was determined and analyzed.The results indicated that the complete mitochondrial genome of O.struma a is circular molecule of 13 957 nucleotides.The gene content includes 22 tRNAs,2 rRNAs and 19 non-coding regions from 2 bp to 138 bp in size.Two protein genes and 4 tRNA genes are transcribed from L strand,and the other 11 protein genes and 18 tRNA genes are transcribed genes from H strand.All protein coding genes of the O.struma mitochondrial genome start with a typical ATN codon,except for ND2 with TTG.The usual TAA or TAG termination codons were found for eleven proteincoding genes.However,the COⅢ and Cytb genes have an incomplete termination codon(T).With respect to the secondary structures of 22 tRNA genes,the absence of DHU arm of tRNA^Ser was observed as in O.struma tRNA^Serand tRNA^Thr with 9 bases in anticodon loop was found,compared with typical 7 bases in others.The longest non-coding has secondary structures similar to the tRNA.Based on the deduced amino acid sequences of 13 proteincoding genes,the phylogenetic tree was constructed with Neighbor-joining(NJ)and Maximum parsimony(MP) methods and the phylogenetic relationships of six gastropoda were discussed．The results demonstrated that O.struma and Platevindex mortoni have closer phylogenetic relationship.

Abstract:This study was undertaken to investigate the effects of dietary nucleotides on growth performance,body composition,tissue biochemical composition and non-specific immunity of juvenile shrimp(Litopenaeus vannamei).960 shrimp(0.43?0.01) g were randomly allocated into 8 groups.The control group was fed with the basal diet,while the other seven groups were fed with the basal diet added with 0.1,0.2,0.4,0.6,0.8,1.0 and 1.2 g/kg mixture of adenosine5′-monophosphate(AMP),cytidine5′-monophosphate(CMP),uridine5′-mono-phosphate disodium salt(UMP),inosine5′-monophosphate disodium salt(IMP)and guanosine5′-monophosphate disodium salt(GMP)(1∶1∶1∶1∶1 W/W,mix-NT)respectively.After 5 weeks feeding,the results showed that weight gain rate(WGR),specific growth rate(SGR)and feed intake(FI)in shrimp fed 0.4 g/kg mixNT were significantly higher than those in the control group(P<0.05).Protein deposit rate(PDR)in 0.6 and 1.0 g/kg groups increased significantly compared with the control group.No significant difference was found among all the treatments in feed conversion rate(FCR),survival rate(SR)and hepatosomatic index(HSI)(P>0.05).The crude lipid and ash content were significantly affected by the dietary mixNT levels(P<0.05),while the dry matter and protein content showed no significant difference(P>0.05).RNA content in hepatopancreas increased significantly(P<0.05)with dietary mixNT increasing,TP content was not significantly affected(P>0.05).TP and RNA content in intestine increased significantly with dietary nucleotides increasing(P<0.05).The uric acid(UA)content in serum decreased significantly in 0.6 g/kg group and glutamic-oxalacetic transaminease(GOT)activity increased significantly in 1.2 g/kg group(P<0.05).Dietary mix-NT significantly increased PO activity in gill,lysozyme(LZM)activity in hepatopancreas and serum(P<0.05).However no significant difference was observed in all the trial groups in glutamic-pyruvic transaminase(GPT)activity,high-density lipoprotein(HDL)content and muscle PO activity(P>0.05).In conclusion,dietary mix-NT could improve growth performance and nutrition metabolism,raise total TP and RNA content in hepatopancrea and intestine,and enhance non-specific immunity of juvenile L.vannamei.