Abstract:A 72-day experiment was carried out to investigate the effect of oxidized fish oil on intestinal mucosa barrier structure and intestinal permeability of grass carp (Ctenopharyngodon idella)[average weight (74.8±1.2) g].Five diets containing different levels of soybean oil,fish oil and oxidized fish oil (6% fish oil,6% soybean oil,2% oxidized fish oil; 4% oxidized fish oil,6% oxidized fish oil) were evaluated according to the equal standards of nitrogen and energy.Using qRT-PCR method,the gene expression levels about atresia protein Occludin,closed protein Claudin3,Claudin15a and cytoplasmic protein ZO-1,ZO-2,ZO-3 in the intestine were measured,and TEM observations of intestinal mucosal cells tight junction and intestinal permeability index were comprehensively analyzed.The results showed that,(1) Serum diamine oxidase activity,endotoxin and D-lactic acid content significantly increased under oxidized fish oil (P<0.05).(2) The gene expression of closed protein Claudin-3,Claudin-15a and cytoplasmic protein ZO-1,ZO-2,ZO-3 were significantly decreased under oxidized fish oil (P<0.05).(3) The tight junction structure of intestinal mucosal cells displayed gap under oxidized fish oil.(4) The values of AV,POV and the content of MDA in diet downregulated with closed protein Claudin3,Claudin15a and cytoplasmic protein ZO-1,ZO-2,ZO-3 gene expression,besides, the value of POV and the content of MDA in diet significantly downregulated with cytoplasmic protein ZO-1 gene expression under oxidized fish oil (P<0.05).Collectively,the present study demonstrated that after adding oxidized fish oil in feed,peroxide oxidation and other oil oxidation product like malondialdehyde of fish oil led to the fact that tight junction protein gene expression activity significantly decreased and tight junction physical structure significant damaged, resulting in the fact that intestinal barrier structure was destroyed and intestinal permeability significantly increased.

Abstract:Vibrio has been widely recognized as a primary pathogen of many commercially cultured invertebrate species the world over.In order to characterize the dynamics of intestinal infection after Vibrio challenge,we investigated the pathological changes and transcriptional response in shrimp Litopenaeus vannamei midgut after bacteria immersion in multiple concentrations.The dynamic changes in intestinal morphology were explored under microscope.Changes in expression of immune genes including anti-lipopolysaccharide factor gene (ALF),penaeidin gene (Pen-4c),crustin gene (Cru),lysozyme gene (LZM) and fatty acid binding protein gene (Fabp) were quantified with qRT-PCR.In addition,the number of Vibrio in intestine and water was also monitored in time courses.To summarize the result,we found slight damage in intestinal tissue in low concentration group at 32 h,medium concentration group at 16 h and high concentration group at 8 h post infection.Severe damages were observed as dose of Vibrio increased and as infection time prolonged,such as the low and medium concentration groups after 40 h or high concentration group after 16 h.Expression level of Cru gene increased at 24 h in low and medium concentration and 16-24 h in high concentration.ALF gene increased at 24 h in low concentration,8-16 h in medium concentration and 16 h in high concentration.Pen-4c gene reached its peak value at 8 h in low and medium concentration and 8-16 h in high concentration.LZM gene was up-regulated at 24 h in low concentration and 8 h in medium and high concentration.Vibrio number in water in all three treatments decreased after infection.Cumulative bacteria in shrimp increased in intestine during 0-8 h and decreased at 32 h.To conclude,midgut damage became worse when bacteria concentration increased or the immersion time prolonged.Gut epithelial cells degraded and collapsed,mucosal folds shrank and ecclasis occurred,as well as the muscular layer was damaged.Within 40 h post infection,shrimp gut morphology deteriorated continuously,and the tissue remained unrepaired.Expression of antimicrobial peptide including ALF,Pen-4c,Cru and LZM increased and this might be used to fight against bacterial infection.However,the expression level of Fabp did not significantly increase.

Abstract:To understand plantigrade settlement of the mussel Mytilus coruscus in response to the different bacterial strains isolated from silanizing surfaces, the relationship between bacterial biofilms and plantigrade settlement was conducted.All test marine bacteria were isolated from the biofilms formed on the silanizing surfaces and identified by 16S rDNA gene sequences.In the laboratory, the effects of monospecific bacterial biofilms on settlement of M.coruscus plantigrades were also investigated.The phylogenetic tree derived from the elected 16S rDNA sequence was constructed and the genetic distance was calculated.The results showed that the density of monospecific bacterial biofilms increased with the initial incubation density and all test bacterial biofilms showed significantly inducing activity on settlement of M.coruscus plantigrades.Among the 9 bacterial species, the biofilms of Staphylococcus sp.1 and Cobetia sp.1 induced the lower percentage of plantigrade settlement of 47% and 43%, and there was no signification correlation between the settlement and biofilm density.The biofilms of other 7 bacteria showed moderate inducing activity, and significant correlation between cell densities of these 7 bacterial strains and inducing activity were observed.The inducing activity of individual bacterial isolates was not correlated with their phylogenetic relationship.Thus, marine bacteria derived from biofilms developed on silanizing surfaces can promote the settlement of plantigrades of the mussel M.coruscus. Those results will provide some useful information to understand the relationship between bacterial biofilms and the settlement mechanism of M.coruscus plantigrades.

Abstract:In order to manage and exploit the loach genetic resources of China,six microsatellites were used to describe the genetic diversity of 7 Chinese loach (Misgurnus anguillicaudatus) populations inhabiting Anhui (AH),Gansu (GS),Guangdong (GD) Guangxi (GX),Heilongjiang (HLJ) and Jiangsu (JS) Provinces and Chongqing (CQ) City,respectively.The 6 polymorphic microsatellites were selected from the microsatellite linkage map of loach,being not linked with each other.They were also found to be in Hardy-Weinberg equilibrium in HLJ population,a less disturbed population,thus being suitable for diversity determination.The 6 microsatellites revealed the polymorphism information content (PIC) ranging from 0.643 to 0.796 among populations.In total,69 alleles were identified,and the number of alleles (N_a) varied between 7 and 16,and the effective alleles (N_e) varied between 3.0 and 5.5.The observed heterozygosity (H_o) among populations ranged from 0.202 to 0.408 while the expected heterozygosity (H_e) ranged from 0.673 to 0.820.These findings indicated that 7 populations were rich in genetic diversity.The co-efficiency of gene differentiation among populations (F_st) was 0.499,illustrating that 49.9% of the total variation can be explained by the differentiation among populations.The F_is ranged from 0.167 to 0.421,indicating that serious inbreeding and further uneven distribution exist within populations.The cluster analysis showed that AH,GD,HLJ and JS populations merged into a clade while CQ,GS and GX fused into the other,indicating that the diversity of Chinese loach may have west-east differentiated and may have been north-south disturbed.

Abstract:The carbon metabolism of microorganisms in biofilters of a recirculating aquaculture system(RAS) cultured with Anguilla marmorata was investigated using Biolog Eco plates.The biofilms were collected from two different tanks of a fluidized bed filter and three different depths of a trickle filter(top,middle and bottom).The results showed that there is no significant difference for Shannon-Wiener index,Simpson index and Pielou index among the biofilms collected from two different tanks of fluidized bed filter and the middle and bottom of trickle filter(P>0.05),all of which was significantly higher than that in the top of the trickle filter(P<0.05).The average well color development(AWCD) and principal component analysis all demonstrated the carbon metabolism of microorganisms in the top of trickle filter was different from other four sample sites.Microorganisms in all sample sites didn't show any preference for any of the six categories of carbon sources.However,the Itaconic acid,D-Galacturonic acid,L-Arginine,L-Asparagine,L-Serine,D-Mannitol,D-xylose,N-Acetyl-D-Glucosamine,Tween 40,Tween 80 and Phenylethyl-amine could be well used by microorganisms from all the sample sites,while γ-Hydroxy butyric acid,α-Ketobutyric acid,D,L-α-Glycerol Phosphate and Glucose-1-Phosphate could not be used by most of microorganisms from all the sample sites.Some carbon sources such as D-Glucosamic Acid,α-D-Lactose,and 2-Hydroxy Benzoic Acid could only be used by microorganisms from certain sample sites.The present study illustrated the properties of carbon metabolism of microorganisms in biofilter of a RAS using Biolog Eco plates and gave a new possibility for water quality control in RAS,which will promote the microbial community changes through regulating the carbon sources in the system to manage the water quality.

Abstract:In the past decades,the natural resources of Rapana venosa in China have obviously declined because of over-exploitation and habitat destruction.It is very necessary to survey genetic diversity and population structure of R.venosa along the coast of China for the formulation of management policies and the protection of R.venosa resources.In the study,nine polymorphic microsatellite markers were used to evaluate the level of genetic diversity of nine wild R.venosa populations along the coast of China and estimate the degree of genetic differentiation among these populations.The analysis of genetic diversity showed that the mean allelic richness ranged from 8.6 to 9.5 and the expected heterozygosity (H_E) ranged from 0.705 to 0.777.The analysis of genetic differentiation showed that the F_ST values ranged from 0.012 2 to 0.093 6 and D_C values ranged from 0.212 to 0.349.It is suggested that the R.venosa possessed high genetic diversity and no clear differentiation was detected between the nine populations.

Abstract:In order to screen microorganisms of degrading ammonia-nitrogen in culture pond,the strain 9A-7and 9A-19 were isolated from the shrimp-shellfish co-culture pond water of Rizhao by degrading ammonia-nitrogen via enrichment culture.The results of molecular biological,physiological and biochemical identification consistently showed that the strain of 9A-7 is Vibrio atypicus and the strain of 9A-19 is Vibrio diabolicus.The results showed that the ammonia degradation ability was related to the growth of the two isolated strains,whose correlation coefficient between the isolated strain cell density and ammonia removal rate is 0.916(9A-7) and 0.938(9A-19),respectively.The ability of degrading ammonia-nitrogen was significantly affected by salinity and pH of the culture solution and culture temperature,and the effect of salinity on ammonia removing rate of two strains was similar and the optimal salinity of both isolated strains was 30,however,the temperature has a less effect on the ammonia reduction rate of the strain 9A-7 than the strain 9A-19,and the weak alkalinity has more remarkable effect on that of the strain 9A-7 than the strain 9A-19.At salinity 30,pH 7.5,temperature 25 ℃,the ammonia reduction rate of the strains 9A-7 and 9A-19 was 90.67%, and 74.67%, respectively.The present results showed that the two isolated bacteria strains are ideal strains for removing ammonia of the culture water.

Abstract:In order to study the role of chitin synthase(Chs) gene from Macrobrachium nipponense in the molting cycle,the M.nipponense chitin synthase(MnChs) of the cuticular tissue was first cloned using rapid amplification of cDNA ends(RACE) method,and its sequence was analyzed with a biological software.Spatio-temporal expression of the MnChs was determined by RT-PCR.The full-length contains 5 133 bp with a 283 bp of 5'-untranslated region(UTR),a 159 bp of 3'UTR and a 4 701 bp of open reading frame encoding a putative MnChs protein of 1566 amino acids with a predicted molecular mass of 179.57 ku and pI of 6.09.It includes two specific tag sequence of Chs(EDR,QRRRW) and a Chitin-synth-C domain.Sequence comparison shows that the MnChs deduced amino acid sequence shares an overall similarity of 89% to Pandalopsis japonica and of 63% to Daphnia pulex.The significant difference of MnChs mRNA levels among tissues is observed during molt stages.The high level occurs at stage A in carapace,at stage D₀ and D₄ in gastrointestine,at stage D₄ in tail fan and muscle.However,the level from hepatopancreas is relatively lower during molt stages.In conclusion,our present results show that MnChs is not only expressed in cuticle,but also in other tissues,and its level change is related to the molting cycle.As a key enzyme catalyzing chitin synthesis,MnChs expression may be involved in the formation of new exocuticle and endocuticle.

Abstract:To study the immune protection of fish vaccinated by the live attenuated Vibrio alginolyticus vaccine,we constructed an in-frame deletion mutant of kdpD/kdpE (kdpDE) genes using overlap PCR and homologous recombination technology,to investigate the effects of this mutant on the biological characteristics.We then compared the differences of the biological characteristics and virulence between the gene deletion mutant and wild strain.Furthermore,the immunoprotection of the vaccine was analyzed by challenge test.The mutant ΔkdpDE showed no differences of ECPase activity and growth from the wild-type strain.But the decreases in swarming ability and biofilm formation were found.Virulence of the mutant declined by 78.5 times in zebrafish model.No bacteria survived in zebrafish 7 days later after injection vaccination.Furthermore,the mutant was used as an antigen to immunize zebrafish.To estimate immunoprotection and immune routes of the live attenuated vaccine,the zebrafish were challenged by V.alginolyticus and V.harveyi at 28 days after immersed and injected vaccination.The relative percentage survival(RPS) value of injection group was 83.3%,and the RPS value of immersion group was 66.7%.The results showed that the ΔkdpDE of V.alginolyticus has a high immunogenicity.In addition,the vaccination led to cross-protection from V.harveyi and the RPS values of injection group and immersion group were 65.5% and 55.2% respectively.These results indicate that the kdpDE mutant is an effective vaccine candidate against V.alginolyticus infection.

Abstract:The scyphozoan Aurelia aurita (Linnaeus) is a cosmopolitan species,having been reported from a variety of coastal and shelf sea environments around the world.The blooms of Aurelia sp.have caused ecological disasters in recent years.In order to discover the key process of the sexual reproduction biology of Aurelia sp.,the spermiation inductive factors,as well as the process of fertilization and embryonic development,were observed according to experimental ecology and microscopy in this study.The results were as follows:the long photoperiod(14L:10D),starvation and damage could effectively induce the sexual matured Aurelia sp.spermiation.The detail information was shown in Tab.1,Tab.2 and Tab.3 respectively.Female Aurelia sp.medusae captured sperm filament that the male released into food bag of somatic edge in which the sperm filament became sperm gobbet by tentacle.The sperm gobbets were transported into oral arm groove by oral arm,then they went through gastric-oral arm groove and gastric reproduction groove successively,and arrived at female gonad to fertilize finally.The fertilized eggs of Aurelia sp.were round and the diameter was about 150 μm.According to the appearance and characteristics of the embryo,embryonic development was divided into 6 consecutive stages:cleavage stage,blastulation stage,blastula stage,gastrulation stage,gastrula stage,planula stage and four tentacles scyphistoma.In (22±1) ℃ sea water,the embryo developed into planula at about 29 h 20 min and grew into four tentacles scyphistoma at about 73 h 20 min.Aurelia sp.Underwent internal fertilization and embryo developed in vivo.The reproductive pattern could improve the survival rate of offspring,which may be the reason why Aurelia sp.existed extensively.

Abstract:Japanese eel(Anguilla japonica)larvae were collected from the Jingjiang Section in the lower reaches of the Yangtze River from January to April of 2012.The concentrations of fourteen elements were measured using synchrotron radiation X-ray fluorescence(SRXRF) to analyze the characteristics of otolith microchemistry in early life phase of the eels in ocean and freshwater.The results showed that Ca and Sr were macroelements in otolith.The contents of other elements ranged from 1 to 10 μg/g(such as Sr,Ba,Fe,Mn and Zn),or were below 1μg/g(such as Cr,Ni,Se,Co,Cu and Au).Ni,Cu,Mn,Cr,Co,Zn and Sr were relatively stable in content and the coefficients of variation(CV) were less than 30%.While Se,Au,Ba and Fe were low and extremely unstable(CV= 40.8%-75.0%).Kruskal-Wallis analysis indicated that the content of Fe significantly varied among individuals(P=0.007<0.05).For eels in seawater life stage,Mn,Se,Co and Ba were highly enriched,and BCF_f was higher than 1 000; whilst Sr,Fe,Zn,Ni and Cu were moderately enriched(100< BCF_a-e <1 000).Except for Sr,Ba and Se,there were no significant differences in enrichment coefficients of otolith between yolksac phase and leptocephalus life phases(P>0.05).For eels in freshwater life stage,Sr and Co were highly enriched(BCF_f >1 000),while Se,Zn,Cu,Ba and Mn were moderately enriched,under which circumstance,BCF_f ranged from 100 to 1 000.In addition,Ni and Fe were slightly enriched(10 < BCF_a-e <100).Compared with seawater life stage,the enrichment of Fe,Ba,Mn,Se,Co and Ni in otolith drastically decreased in freshwater.These results indicate that Sr,Ba,Ni and Co are highly responsive to environmental conditions,while Fe and Mn are rarely responsive,and Zn,Cu and Se are negatively responsive.Because environmental high response elements required time lag to pass through physiological barriers before being incorporated into otoliths during migration from seawater to freshwater and because the contents of environmental weak response and negative response elements fluctuated greatly and lacked regular rules to respond to environmental conditions changes,we propose that the following characteristics could be used as the element indicator to reflect fish's migratory behaviors or monitor environmental hydrochemistry:high enrichments in otoliths,weak time-lag responsive to environmental changes,high concentration gradient between different water environment,stability of content and non-essentials and so on.Obviously,Sr and Ba conform to these conditions and could be used as the indicator elements.

Abstract:Nile tilapia (Oreochromis niloticus) is one of the widely cultured fish species in the world,and has been known as a good raw material in seafood processing field.In this paper,the changes of biochemical properties of muscle protein from Nile tilapia fillets sterilized by ozone treatment during iced storage were investigated by changes evaluation of myofibrillar protein salt solubility,Ca²⁺-ATPase activity,surface hydrophobicity of actomyosin,total sulfhydryl content of actomyosin and carbonyl content.The results showed that different degrees of protein degeneration of ozone-water pretreatment group and control group Nile tilapia fillets all occurred during iced storage.The myofibrillar protein salt solubility,Ca²⁺-ATPase activity and total sulfhydryl content all decreased as the storage time was extended.Moreover,both surface hydrophobicity of actomyosin and carbonyl content increased during iced storage.After being stored for 20 days,the myofibrillar protein salt solubility,Ca²⁺-ATPase activity and total sulfhydryl content of ozone-water pretreatment group decreased by 76.57%,89.76% and 66.72% respectively,while those of control group declined by 69.05%,86.45% and 62.29%.On the other hand,surface hydrophobicity of actomyosin and carbonyl content of ozone-water pretreatment group increased by 111.75% and 76.46% respectively,while those of control group rose by 104.77% and 58.23%.At the same storage time,the myofibrillar protein salt solubility,Ca²⁺-ATPase activity and total sulfhydryl content of ozone-water pretreatment group were lower than those of control group,and both surface hydrophobicity of actomyosin and carbonyl content were higher than those of control group.The research results indicated that the protein denaturation was promoted by the oxidation of ozone-water and ROS generated from ozone-water during storage period.

Abstract:To discuss formation mechanism of biogenic amines in fish during pickling and drying preliminarily,dynamic change and the mutual relationship of salinity,moisture content,Aw,pH,protein hydrolysis index (P.I.),Non-protein nitrogen (NPN),free amino acid,microorganism,biogenic amines and relevant biogenic amine indices in hairtail (Trichiurus lepturus) during pickled and dried processing were studied.The results showed that,the pH in curing phase increases but fell in a dry stage.Salinity,P.I.,total plate counts,lactic acid bacteria,micrococcus and staphylococcus contents increased generally during process stage but moisture content and Aw continued to decline.There has been a marked protein degradation reaction,the content of NPN and free amino acids considerably increase,the total biogenic amine content increased 2.26 times,which cadaverine content significantly increased by 157 times,followed by histamine during whole process stage.Free amino acid and biogenic amines was significantly positive correlation,as the biogenic amine precursor to influence on the formation of biogenic amines,the microbes have played an important role in promoting and inhibition of biogenic amines,the formation of biogenic amines are affected by factors such as pH,salinity,Aw,mutual influence,is an extremely complex process in hairtail pickling and drying process.

Abstract:In this paper,a chromosomal observation on different growth phases of Pyropia chauhanii from India was conducted.The living materials of different life phases in P.chauhanii were fixed in Carnnoy's fixative fluid,and stored at the light conditions to leach phycobilin pigments.The samples were then stained with Wittmann's aceto-iron haematoxylin chloral hydrate and examined under a photomicroscope.Chromosome counts indicated that vegetative cells of gametophytic blade,spermatia and carpogonium are haploid (n=3); whereas carpospores,vegetative and conchosporangial cells of conchocelis are diploid (2n=6).The meiosis happened during the first division of the germinating conchospores,and after that,the chromosome changed from diploid to haploid.The spontaneous chromosome doubling occurred in the carpospore-like cells during the parthenogenesis of the gametophytic blades,and chromosome counts indicated that the germinating carpospore-like cells,their germ-tube cells,the vegetative cells and conchosporangial branch cells of parthenogenetic conchocelis are diploid (2n=6).Monospores and the cells of their germlings are haploid (n=3).The above results showed that the haploid and diploid phases of P.chauhanii have 3 and 6 chromosomes,respectively.

Abstract:Within the ecosystem of macroalgal bed of Gouqi Island offshore,small invertebrates such as zooplankton,amphipod,polychaetes and echinodermata were important parts of the food web,which bore the responsibility of transferring the energy of the primary producers to advanced consumers.To find out the food sources of copepoda,Euphausia pacifica,Acetes chinensis,Acetes chinensis,Halosydna brevisetosa,Mytilus coruscus,Turbo cornutus,Anthocidaris crassispina,gammaridae,caprellidae,Spongia,gammaridae larvae etc.,this research analyzed the carbon and nitrogen stable isotope composition of small invertebrates and primary producers including phytoplankton,macroalgae,microalgae etc.Meanwhile,the research estimated the food source contribution rate of primary producers to small invertebrates by using IsoSource multi-source linear mixed model.The results showed the δ¹³C value of primary producers was between -21.7 ‰ and -13.8 ‰,and the δ¹⁵N of primary producers was between 2.3 ‰ and 11.6 ‰. The stable isotope composition of primary producers had different varitions between the period of autumn and winter and that of spring and summer.Among them,the δ¹³C value of SOM,phytoplankton,POM and Sargassum horueri had no significant seasonal difference(P>0.05),while the δ¹³C value of epiphyte,Ulva pertuca and benthic microalgae had significant seasonal difference(P<0.05).Among all the primary producers,only the δ¹⁵N values of epiphyte had very significant seasonal difference,while the δ¹⁵N value of all the others had no significant seasonal difference.The δ¹³C value of small invertebrates was between -20.3 ‰ and -15.4 ‰,and the δ¹⁵N of small invertebrates was between 2.5 ‰ and 8.1 ‰.Meanwhile,among all the small invertebrates,only the δ¹³C and δ¹⁵N value of copepoda had significant seasonal difference(P<0.05),while the δ¹³C and δ¹⁵N values of all the others had no significant seasonal difference(P>0.05).Based on the multi-source linear mixed model,the research found phytoplankton was the main carbon source of Spongia and zooplankton such as Copepoda,Euphausia pacifica and Acetes chinensis.Caprellidae and Gammaridae larvae etc.mainly fed on epiphyte.As to small benthic invertebrates,such as Gammaridae,Anthocidaris crassispina and Turbo cornutus etc.,their main nutrition sources were macroalgae and benthic microalgae.

Abstract:High density polyethylene produced by Qilu Petrochemical Engineering Co.Ltd was melt-spun by screw extruder and then multi-step drawn at high temperature to fabricate high performance fishery PE fibers.It was showed that when the draw ratio was 8.17 in the one-step process,the breaking strength and knot strength of the PE fiber were 5.71cN/dtex and 4.56cN/dtex,respectively; but when the first and total draw ratio were 8.17 and 9.52 in the two-step process,the breaking strength and knot strength were 7.91cN/dtex and 5.24cN/dtex,which were 41.3% and 34.4% higher than the high-class products specified in the national standard,respectively.It was found that the PE fibers fabricated by two-step process showed more regular macromolecular chains,higher orientation and better fishery properties than those fabricated by one-step process.In addition,with the total draw ratio increased,the breaking strength,sound orientation and thermal properties were improved,but the knot strength increased first and subsequently decreased.

Abstract:Six isonitrogenous and isolipidic diets with increasing digestible starch levels (5.93%,8.71%,11.96%,15.11%,18.16%,21.74%) were formulated to determine suitable level of digestible starch in diets for largemouth bass (Micropterus salmoides),based on growth performance,body composition,serum glucose and non-specific immunological index.Each diet was randomly assigned to triplicate tanks,in each of which 35 fish with an average initial weight of (28.36±0.10) g were stocked.Fish were fed to apparent satiation twice daily (8:00 and 16:00) for 48 days.At the end of feeding test,the lowest survival rate was showed with fish fed a diet containing 21.74% dietary digestible starch (DDS) (P<0.05).Final body weight,specific growth rate and feed intake occurred to a significant declining tendency with DDS levels being higher than 8.71% (P<0.05).Feed efficiency and protein efficiency ratio,however,were the highest with fish fed 11.96% DDS (P<0.05).With an increasing DDS level,apparent digestibility coefficients (ADCs) of dietary lipid and starch were found to be lower (P<0.05),but ADCs of dietary protein showed no significant differences (P>0.05).Meanwhile,in the whole body,muscle,viscera and liver of test fish,protein concentrations significantly decreased,but lipid concentrations became the highest in fish fed the diet containing up to 8.71% DDS,and then declined (P<0.05).With a DDS level increasing,hepatosomatic index,viscerosomatic index,liver glycogen content,activities of serum alanine aminotransferase and aspartate aminotransferase significantly increased,but hemoglobin content gradually declined (P<0.05).In fish fed diets containing higher than 11.96% DDS,serum glucose concentrations constantly increased from 3 to 12 h postprandial,and a continuous hyperglycaemia was observed.The highest serum protein content and complement activity (CH50) were found with fish fed the diet with 8.71% DDS (P<0.05),whereas activities of serum lysozyme and respiratory burst of head kidney leukocytes occurred to fish fed the diet with 11.96% DDS (P<0.05).Based on broken-line regression analysis of specific growth rate and protein efficiency ratio against DDS levels,the suitable inclusion levels of digestible starch in the diet for largemouth bass were 9.22% and 10.05%,respectively.It can be concluded from this study that largemouth bass have a limited ability to utilize DDS efficiently.