Abstract:The present study was conducted to estimate the quantitative requirement of L-isoleucine in Japanese seabass(Lateolabrax japonicus)[initial body weight(159.33±1.20)g]by feeding six isonitrogenous and isoenergetic practical diets containing graded levels of L-isoleucine 0.72%, 1.11%, 1.53%, 1.93%, 2.31% and 2.72%(dry weight), respectively, named diet 1—diet 6.After a 10-week growth trial, results showed that weight gain rate(WGR), feed efficiency(FE)and protein retention(PR)were significantly influenced by the different diets(P<0.05).The values increased first, and then declined as the dietary L-isoleucine levels increased.The highest values of these three parameters were 108.55%, 0.89 and 37.57% in fish fed the diet with 1.93% dry matter of dietary L-isoleucine, respectively.Survival rate(SR), feed intake(FI), hepatosomatic index(HSI), viscerosomatic index(VSI), condition factor(CF), body composition and the essential amino acids of muscle were not significantly influenced by dietary L-isoleucine level(P>0.05).Dietary L-isoleucine significantly affected the activities of glutamic-oxaloacetic transaminase(GOT)and glutamic-pyruvic transaminase(GPT)in livers(P<0.05).The level of triglicerid(TG)in serum was significantly affected by dietary L-isoleucine levels(P<0.05).Fish fed the diet with 1.93% L-isoleucine had the highest TG value.GOT and GPT activities and total cholesterol(TC)levels in serum were not significantly affected(P>0.05).In conclusion, appropriate dietary L-isoleucine level can improve the growth of the seabass.On the basis of WGR and PR, using the second-order regression analysis, dietary L-isoleucine requirement of Japanese seabass in the middle growing stage were estimated to be 1.88% and 1.84% dry diet(4.41% and 4.32% dietary protein), respectively.

Abstract:The nutritional effects of dietary taurine on the growth, body composition and tissue free amino acid concentrations in Nile tilapia were evaluated.Three hundred tilapias[initial body weight(5.89±0.03)g]were randomly divided into five groups with three replicate tanks at a stock density of twenty fish in each replicate.Five diets were formulated to contain 0, 0.4%, 0.8%, 1.2%, and 1.6% taurine and were allocated to each of the groups of fish twice a day for a feeding period of 56 days.The fish fed the diet at 0.8% taurine got highest weight gain(P<0.05).Dietary taurine levels at 0.4%-1.6% increased feed intake, hepatosomatic index and viscera index, but reduced feed conversion ratio(P<0.05);Both whole-body moisture and ash contents decreased but whole-body crude protein and lipid contents increased with the increase of dietary taurine level(P<0.05);Quadratic curve analysis indicated that the optimal level of dietary taurine for tilapia growth was 0.75% based on weight gain.Taurine concentrations in serum, liver, muscle and whole-body fish were positively linearly correlated with the dietary taurine levels, and the values for these tissues in taurine-treated groups were significantly higher than those of control group(P<0.05).With the increase of dietary taurine, free amino acid concentrations in liver and muscle gradually decreased, and the values in taurine-treated groups were significantly lower than those in control group(P<0.05).

Abstract:An 8-week feeding trial was conducted to evaluate the effects of crystalline and capsulated DL-methionine on fish meal replacement with soybean meal in diets for Japanese seabass Lateolabrax japonicus.A reference diet(control)was formulated to contain 40% fish meal.A 2×4 layout was used, including two fish meal replacement levels(40% or 80% of the fish meal in control diet were replaced with soybean meal)and four types of DL-Met supplementation(A:Crystalline DL-Met;B:Capsulated DL-Met;C:Crystalline DL-Met + capsule material;D:a premix containing B and C at 1:1).The 8 test diets were formulated isonitrogenous and isolipidic.0.5% A, 1.3% B, 1.3% C or 1.3% D were added in diets LA, LB, LC and LD(dietary fish meal level was 24%), respectively, while 0.7% A, 1.8% B, 1.8% C or 1.8% D were added in diets HA, HB, HC and HD(dietary fish meal level was 8%).Initial body weight of Japanese seabass was(6.0±0.1)g.Fish meal replacement level significantly affected weight gain(WG), feed intake(FI), feed conversion ratio(FCR), nitrogen retention efficiency(NRE), total nitrogen wastes output(TNW), hepatosomatic index(HSI)and proximate composition of whole fish(P<0.05);while types of DL-Met affected total phosphorus wastes output(TPW)(P<0.05).The WG and NRE decreased(P<0.05), while the FCR and TNW increased, with increasing of fish meal replacement level, whether crystalline or capsulated DL-Met was added.At the same fish meal replacement level, no significant differences were found in the WG, FCR, NRE, CF, HSI, body composition, TNW and TPW between fish fed the diets with supplementation of A, B, C or D(P>0.05).This study indicates that dietary fish meal level for Japanese seabass can be reduced to 24% when SBM was used as a fish meal substitute, and supplentation of crystalline or capsulated DL-Met could not enhance fish meal replacement level by SBM in diets for Japanese seabass.

Abstract:The aim of this paper is to investigate the toxic effects of ammonia-N stress on the histopathological changes of gill, liver and kidney of juvenile Megalobrama amblycephala.The M.amblycephala, whose initial average weight was(14.27±0.01)g, were first exposed to ammonia-N for 96 hours and then obtained the 96 hours median lethal concentration.Based on this, the juvenile M.amblycephala were exposed to two ammonia-N levels:0.472 mg/L(control group)and 25 mg/L(experimental group), each ammonia-N level was respectively sampled at 0, 6, 12, 24, 48 h, then the remainder of them were moved into aerated tap water for a 96 h post-exposure recovery.The results showed that the 96 h LC₅₀ of ammonia-N were found to be 56.492 mg/L.Fish exposed to different ammonia concentrations displayed histopathologic alteraions in the gills, liver and kidney.Gill tissues displayed hyperemia, epithelial hyperplasia, chloride cell hyperplasia, telangiectasis, epithelial necrosis and desquamation, epithelial and oedema, lamellar fusion curling of secondary lamellae as well as shortening of secondary lamellae.The liver showed hypertrophy of hepatocytes, cloudy degeneration, karyolysis, cellular peripheral nucleus, nuclear hypertrophy, hepato cellular vacuolation, dilatation in sinusoids, congestion, hydropic degeneration, necrosis, cellular outline indistinguishable and cytolysis;hypertrophied epithelial cells of renal tubules, reduction of space inside renal tubules, expansion of space inside, Bowman's capsule, contraction of the glomerulus, necrosis in tubular epithelium, cloudy swelling of epithelial cells of renal tubules, tubular necrosis, lymphocytic cell infiltration, renal tubules epithelial cells vacuolation, hydropic degeneration and hyperemia were observed in kidney.The results indicate that the severity of lesions clearly differed among organs with the liver showing the most extensive damages followed in order by the gills and kidney.The damages of gill, liver and kidney increase with increasing exposure time, in the meanwhile, the fish showed the self-regulation ability, however, it could not fully recover after a 96-hour post-expourse recovery and the kidney showed the worst recovery ability.

Abstract:In order to investigate the intestinal bacterial community comparison and its relationship with environmental factors, intestine samples were collected from pond and indoor tank-cultured Japanese flounder, Paralichthys olivaceus, and the composition, diversity and origin of bacterial community in them were investigated based on high throughput sequencing of 16S rRNA gene and six other samples from culture-associated environmental factors including culture water, feeds and pond sediment was also collected and their microbiota composition was also investigated using sequencing of 16S rRNA gene.The results showed that the dominant bacterial community harboring in pond-culture Japanese flounder intestine were Firmicutes(30.49%), Proteobacteria(19.16%), Fusobacteria(11.11%), wherein the most abundant bacteria was Bacillus(27.66%)and the least abundant was Vibrio based on genus level;whereas for pond-culture Japanese flounder, its intestine holds a core microbiota composed of Proteobacteria(44.31%), Firmicutes(11.57%), Actinobacteria(4.79%), in which the most abundant bacteria were Acinetobacter and Vibrio based on genus level.The most abundant bacterial operational taxonomic units(OTUs)in the Japanese flounder intestinal content are those related to nutrition metabolism, and the potential pathogens and probiotics are also important members of the intestinal microbiota.Differences and phylogenetic analysis revealed that the composition, diversity and origin of Japanese flounder intestinal bacterial communities were closely related with feed, followed by culture water.The present results would not only facilitate production of high-efficient probiotics, but also could provide theoretical support for construction of practical micro-ecological technology for P.olivaceus under different culture environment.

Abstract:To evaluate the mechanism of different spoilage potential of the specific spoilage organism(SSO), Shewanella, H₂S-producing bacteria isolated from the refrigerated Larimichthys crocea were identified using the physicochemical reactions and 16S rDNA.Four strains with different spoilage potential were selected in the sterile fish juice and fish block.The gene and expression of trimethylamine oxidation(TMAO)reductase in four strains were amplified and determined, and physicochemical properties of the protein were predicted.The results showed that all H₂S-producing bacteria were identified as Shewanella, in which S.baltica, S.putrefaciens and S.hafniensis accounted for 54.5%, 40.9% and 4.5%, respectively.Significant differences of the spoilage potential were in fish juice among Shewanella observed.The sensory score and TVB-N content of isolates S.baltica XH2 and XH8 were significantly higher than those of the other strains(P<0.05), whereas the indicators of isolates S.putrefaciens XH14 and XH17 were the lowest.The sample inoculated S.baltica XH2 was found to produce off-odors after 72 h, higher than 10⁷ cfu/g of TVC after 48 h, strong reduction ability of TMAO to TMA, high accumulation of TVB-N, cadaverine and putrescin, followed by S.baltica XH8, S.putrefaciens XH14 and XH17.The 2 490 bp fragment of torA gene were amplified in four Shewanella isolates.Expression of torA gene of four isolates was correlated with the spoilage potential.Furthermore, the highest molecular weight and aliphatic index of predicted TorA protein were observed, whereas theoretical pI and gravy were the lowest in S.baltica XH2.Thus, SSO in chilled L.crocea was S.baltica XH2, and the high spoilage potential in the isolate was associated with high level of torA expression and some physicochemical properties of TorA protein.It provides a good foundation to clarify the mechanism of spoilage in Shewanella.

Abstract:Phospholipid hydroperoxide glutathione peroxidase(PHGPx)is one of the members of GPx family, which has its unique ability to reduce hydroperoxides in complex lipids such as phospholipid, cholesterol and so on.PHGPx is a key enzyme in the antioxidant defense systems of living organisms, including crustaceans, which plays important roles in the effect of antioxidant and sexual maturity of male.In this study, expressed sequence tag(EST)of Scylla paramamosain PHGPx gene was identified from transcriptome sequencing library and the full length cDNA was cloned by SMART-RACE method, which was named Sp-PHGPx.The full-length cDNA of Sp-PHGPx is 1 024 bp, including a 5'UTR of 140 bp, a 3'UTR of 341 bp and an open reading frame of 543 bp, encoded a duduced protein of 180 amino acids.Sequence comparison and phylogenetic analysis showed that Sp-PHGPx was clustered with PHGPx(GPx4)of other species, far from GPx1 and GPx2.Quantitative real time PCR revealed that Sp-PHGPx was expressed in various tissues of the mature female and male crabs with the highest expression level in testis.During the different stages of gonadal development, there was no significant difference in the development of ovary;while Sp-PHGPx was expressed at the highest level in spermatid stage(T2)and was significantly higher than spermatocyte stage(T1)and mature sperm(T3)during the development of testis.Moreover, the expression levels of T2 are higher than these of other stages of ovary development.When under the challenge of LPS, the expression level of Sp-PHGPx was up-regulated significantly at 6 h in gill and at 12 h in hepatopancrea compared with control.The expression of Sp-PHGPx in gill was induced significantly at 3 h, while there was no significant difference in hepatopancrea when exposed to H₂O₂.Above results suggest that Sp-PHGPx may be involved in immune defense and the male reproduction in S.paramamosain.

Abstract:In order to explore the change characteristics of fat oxidation in refrigerated dorsal and belly Salmo salar fillets, and to establish and validate the shelf-life model based on the fat oxidation indicators, acid value(AV), peroxide value(POV), thiobarbituric acid value(TBA)and sensory evaluation were measured periodically during cold storage.Results showed that the acid value, peroxide value and thiobarbituric acid value of dorsal and belly S.salar fillets showed an increasing trend with the extension of storage time.At the same time, sensory evaluation score decreased gradually.The changes of belly fillets were more obvious than those of dorsal fillets, and the higher the temperature was, the more significant the fat oxidation indexes were.The fat oxidation indexes of dorsal and belly S.salar fillets were consistent with the first-order chemical reaction dynamic model.It was found that POV value and TBA value were well fitted by the first-order chemical reaction kinetics model(R²>0.90)and there was a relatively good accordant effect of AV value with the first-order chemical reaction kinetics model(R²>0.82).Arrhenius equation was used to establish the dynamic model of AV value, POV value and TBA value for dorsal and belly S.salar fillets, and there was a higher fitting accuracy(R²>0.90).The established activation energy E_A of AV value, POV value and TBA value for dorsal fillets in the dynamic equation were 47.309, 81.611 and 35.560 kJ/mol, respectively.The activation energy E_A of belly fillets were 77.628, 55.686 and 19.399 kJ/mol, respectively.The established predictive shelf-life models of dorsal and belly S.salar fillets showed that the relative error of predicted value and actual value was within ±10.60%.Therefore, the shelf-life of S.salar fillets in refrigerated storage could be well predicted by these models.

Abstract:The aim is to study the genomic characteristics and evaluate the candidate microsatellites(or simple sequence repeat, SSR)isolated via a genomic survey for genetic linkage mapping of Chinese mitten crab Eriocheir sinensis.In this study, a set of 60 candidate tri-nucleotide microsatellite markers were randomly selected.Their validation and polymorphism were investigated in an F₁ family of mitten crab using the genomic DNA of the parents and 6 offspring, and the segregation patterns and linkage relationship of polymorphic loci were subsequently investigated in 80 F₁ individuals.The results are as follows:Forty-two primer sets(70.00%)successfully yielded amplicons.The number of alleles per locus of the family varied from 1 to 4, and the number of alleles for each individual per locus was 1 or 2.In the 42 SSRs, 5 SSRs were mono-morphism and 37 SSRs were polymorphism.In the 37 polymorphic loci analysed using the F₁ family, twenty-three loci exhibited a segregation ratio of 1:1:1:1, eleven loci exhibited a segregation ratio of 1:1, and three loci exhibited a segregation of 1:2:1.Polymorphism analysis showed that 35(94.59%)SSRs consisted with Mendelian segregation ratio, while the other 2(5.41%)SSRs(scaffold430598_213690 and scaffold21303_16865)deviated from the expected Mendelian segregation pattern.Linkage analysis showed that scaffold240262_150253, scaffold216209_138892 and scaffold293154_172768 had linkage relationship, scaffold285640_16972 and scaffold427534_212914 had linkage relationship, and so had scaffold507500_231891 and scaffold92860_68250.The results suggest that the Chinese mitten crab were diploid and its genetic linkage map could be constructed using the candidate SSRs and an F₁ family.

Abstract:In this study, according to the survey data of tuna purse seine by sea trials from 2011 to 2014, by using the Bootstrap and generalized additive model(GAM)to quantitatively analyse the differences gear performance between free swimming school and floating objects fishing methods.The results show that:(1)the maximum sinking depth of floating objects fishing method(195.20-219.36 m)is 94.8% of free swimming school fishing method(205.83-219.04 m);The average sinking speed of the floating objects fishing method(0.152-0.176 m/s)is 84.4%-91.2% of free swimming school fishing method(0.180-0.193 m/s).(2)V₁₀, V₆₀ and L₁ have a significant impact on the sinking speed for the swimming school fishing method.(3)V₆₀, L and V₀ have a significant impact on the sinking speed for the fishing floating objects associated school.(4)The results by GAM prediction show that:the predicted values of sinking speed(0.155-0.175 m/s)is 99.4% of sea trials for the floating objects fishing method;the predicted values of sinking speed(0.182-0.190 m/s)is 98.4% of sea trials for the free swimming school fishing method.These results can provide some reference for distinguishing the sea conditions and controlling the fishing operation for sea operation.

Abstract:Small heat shock proteins(sHsp), representing an important molecular chaperone in eukaryotic cells, play important roles not only in a variety of stress responses, but also in development and signal transduction of normal cell.In this study, based on unigene sequences which were obtained from whole transcriptome sequencing of Pyropia haitanensis, two full-length sHSP genes were obtained by rapid amplification of cDNA ends(RACE)or direct PCR, which named PhHsp22 and PhDnaJ.The full-length cDNA of the PhHsp22 gene comprised 857 nucleotides and contained an open reading frame of 519 bp(GenBank accession:KM102540), encoding a protein of 172 amino acid residues with the predicted molecular weight of 19.1 ku and theoretical isoelectric point of 5.24;the full-length cDNA of the PhDnaJ gene comprised 1 616 nucleotides and contained an open reading frame of 1 290 bp(GenBank accession:KM102541), encoding a protein of 429 amino acid residues with the predicted molecular weight of 46.1 ku and theoretical isoelectric point of 6.43.On the basis of conserved motifs and phylogenetic tree analysis, PhDnaJ belongs to the subfamily of Hsp40.The expressions of the two genes, as measured by real-time quantitative PCR, were significantly induced by high-temperature stress and desiccation stress, and had identical expression patterns:during high-temperature and desiccation stress, the expression levels of the two genes all significantly increased firstly and then decreased.These results suggested that the expressions of PhHsp22 and PhDnaJ genes are feedback regulated by high-temperature and desiccation stresses.

Abstract:In this paper, for obtaining the influence of otter board on the mechanical trawl system matching calculation, trawl system mechanical matching calculation model was established based on the equilibrium equation of otter board and tension equation of wire rope, a widely used cambered V type otter board was selected, the hydrodynamic performance experiment data, combining with the data of 'Longteng' vessel and four patch and big mesh size mid water trawl experiment results were taken into the model, calculation and analysis was conducted from the tension of trawl wing tip, to the sweep line, otter board, wrap step by step, the attack angle, warp tension, warp length, net depth and other trawl system parameters value were obtained.The influences of otter board parameters on trawl system operation and force situation was analyzed, and it was proved that:Attack angle decreases with the increase of the drag velocity;warp tension and net depth increases exponentially with the increase of Z coordinate of warp line junction, decreases linearly with the increase of Z coordinate of sweep line junction; attack angle was controlled between 17.77°-18.55°, net depth between 124.3-192.3 m, and warp tension between 40 210-42 219 N via the Z coordinate of warp line junction was adjusted between 0.1-0.6 m;attack angle was controlled between 16.54°-19.85°, net depth between 75.9-679.5 m, and warp tension between 39 533.5-57 933 N via the Z coordinate of sweep line junction was adjusted between -0.4-0.05 m;trawlers loading decreases with the decrease of otter board weight, and be more suitable for shallow operation; attack angle and trawlers loading decreases with the decrease of otter board area, and be more suitable for deep layer operation.The rules of mechanical matching calculation versus otter board parameters were summarized, and the estimation equations were obtained, and reference for correct using and further development of otter board were provided.

Abstract:The filaments of Scytosiphon lomentaria preserved in our laboratory were used as the experimental material, and the effects of five culture media L1, PES, F1, f/2 and ESNW on the growth and development of filaments of S.lomentaria were studied, meanwhile, the effects of the different concentrations of nitrate and phosphate based on NO₃^--N and PO₄^3--P free of L1 culture medium on the growth and development of filaments of S.lomentaria were also studied by the experimental ecology methods in this paper.Results showed as follows:(1)L1 was the optimal culture medium for the growth and development of filaments of S.lomentaria in the five culture media.The filaments of S.lomentaria were dark brown and the cytoplasm was plentiful cultured in L1 medium, the increasing ratio of filament biomass was(560.48%±0.73%), the sporangial branchlets ratio and the sporangium diameter could reach up to(46.88%±0.41%)and(18.95±0.89)μm, respectively, after being cultured for 28 days in L1 culture medium;(2)The optimal concentration of NO₃^--N for the growth and development of filaments of S.lomentaria was 6.00 mg/L.Under this concentration, the filaments could grow rapidly and the filaments of S.lomentaria were dark brown, moreover the sporangial branchlets ratio could achieve(46.78%±0.14%)and the sporangium diameter could increase to(18.78±2.45)μm after being cultured for 20 days.Whereas, the filaments grew slowly and pigment of the filaments of S.lomentaria was light with the addition of NO₃^--N at the concentrations of 0, 96.00 and 192.00 mg/L, the sporangial branchlets ratio were(0%±0%), (9.06%±0.32%)and(7.65%±0.45%), respectively, and the sporangium diameter were only about 9.00-10.00 μm after being cultured for 20 days;(3)The optimal addition concentration of PO₄^3--P for the growth and development of filaments of S.lomentaria was 1.32 mg/L.Under the concentration, the filaments could grow rapidly, moreover, the filaments of S.lomentaria were dark brown, the sporangial branchlets ratio could achieve(47.12%±0.26%), the sporangium diameter was 18.89 μm after being cultured for 20 days.However, the sporangial branchlets ratio was only(18.89±0.98)μm and the sporangium diameter was just(9.78±1.32)μm after being cultured for 20 days with the addition of PO₄^3--P at 0 mg/L, and the filaments of S.lomentaria were turned virescent, the cells were cytoclasis and there was no formation of the sporangial branchlets with the addition of PO₄^3--P exceeding 15.84 mg/L.The results mentioned above revealed that it was good for the filaments of S.lomentaria to grow rapidly, enhance the sporangial branchlets ratio and magnify sporangium diameter based on selecting a suitable culture medium and controlling the concentration of nitrate and phosphate within limits in the stage of growth and development of filaments of S.lomentaria.

Abstract:Owing to lack of recombination, maternal inheritance, absence of introns and higher evolutionary rates, mitochondrial DNA(mtDNA)are extensively used for population genetics, species identification and phylogenetic relationships at various taxonomic levels.In recent studies, phylogenetic analysis based on mtDNA sequence data has been proved to enhance resolution and statistical confidence of inferred phylogenetic trees when compared with traditional taxonomic methods.Taxonomy and phylogeny of Cephalopoda, which is by far one the most important economic and diversity group of mollusks, have become the most intriguing field.Herein, we provided a brief introduction to the contents and the structures of mtDNA, and subsequently reviewed the progress of mtDNA applied in cephalopod molecular systematics, especially the complete genome.Additionally, the research tendency of molecular systematics of cephalopods was discussed.