Abstract:Genetic parameters of growth and upper thermal tolerance traits of turbot Scophthalmus maximus were analyzed based on the data collected during experiments with 753 individuals from 40 families of turbot that were exposed to a thermal tolerance challenge,and two animal models were established by including a common full-sib effect or inverse.The variance components in each model were estimated with the average information restricted maximum likelihood method using WOMBAT software,and the differences between the two models were tested by likelihood ratio test.The results showed that better estimation was achieved with model Ⅰ for estimating genetic parameters of body weight and upper thermal tolerance,whose heritability was(0.22?0.09)and(0.026?0.034),respectively.The differences between genetic parameters of relative fatness by the two animal models were not significant,and the range of heritability was (0.21?0.18)-(0.39?0.11).The correlation analysis showed that the phenotypic correlation coefficients between body weight and relative fatness,body weight and upper thermal tolerance were 0.13 and 0.04,respectively,while the phenotypic correlation coefficient between relative fatness and upper thermal tolerance was 0.13.The genetic correlation coefficients between body weight and relative fatness,body weight and upper thermal tolerance were 0.01 and -1.00,respectively.The genetic correlation coefficient between relative fatness and upper thermal tolerance was 0.05.The results indicated that model Ⅰ without including a common full-sib effect was better than model Ⅱ to be used to estimate the genetic parameters in this study.

Abstract:The secreted proteins of Vibrio anguillarum MN,V.anguillarum-3101 and Vibrio fischeri which were isolated and conserved by our laboratory,were extracted.The components of secreted proteins were separated by SDS-PAGE.The 5 high expressed protein bands in the SDSPAGE were identified by mass spectrometry MALDI-TOF/TOF as the metalloprotease of V.anguillarum-MN,the metalloprotease of V.anguillarum-3101,the zinc metalloproteinase of V.anguillarum-3101,the hypothetical protein VFMJ11_1094 and outer membrane protein of V.fischeri-ES114.After downloading the sequences of above proteins from NCBI database,PCR primers were designed and specific DNA bands were amplified,cloned and sequence analysed.5 signal peptides were given by using the online software SignaIP 3.0,namely angMN-35,ang3101-35,ang3101-25,vf-38 and vf-23.The cellular were localization of the secreted sequences were analyzed by PSORT.And we found that all the signal peptides located in the outer membrane or periplasmic space of the cell.The results may be useful for construction of a secreted vector.

Abstract:The karyotype of Verasper variegatus was studied through the chromosome preparations obtained from head kidney by the method of injecting PHA and colchicines.Metaphase chromosomes were analyzed by means of C-banding,Ag-NORs and G-banding.Experiment results showed that the diploid chromosome number of V.variegatus was 46(2n=46t,NF=46).There was no visible evidence of sex chromosome and satellite chromosome.C-bands of V.variegatus were located mainly in the centromere regions of chromosomes except the No.19 and 22 chromosomes,and the 19th pair of chromosomes showed positive C-bands in the terminal region while the whole 22th pair of chromosomes bore positive C-band thoroughly.The C-banding heretochromatin accounts for 30% of the total chromosome surface in V.variegatus.Silver staining study showed that V.variegatus bore a pair of Ag-NORs which was located at the end of long arm of the 2nd chromosome.A total of 59 positive G-bands(38 dark,21 light)were recorded in 23 pairs of chromosomes.These results would provide basic data for the genomic research and biodiversity conservation of V.variegatus.

Abstract:In consideration of the differences between Neomysis awatschensis and Neomysis japonica in the growth,reproduction,susceptibility and other aspects,the susceptibility of two Neomysis to Vibrio alginolyticus was studied,which could help to explore to the root of the phenomenon in immunology.Two staining methods of Giemsa and wright’s were used in this experiment of the haemocytes of the adult N.awatschensis, and haemocytes of the mysis were classified base on the large/small size,the presence/absence of cytoplasmic granules,the number of granules,and nucleus to cytoplasm(N/C)ratio and the proportion of various haemocytes were also carried out.The results of these studies showed:three types of haemocytes were identified in N.awatschensis hyaline cells,semigranular cells,granular cells,ascending in the size and declining in the N/C ratio,successively.To further check the statistics of the rate of three types haemocytes,the observations indicated that the highest rate of granular cells was about(48.38%?0.05%),the lowest of hyaline cells about(16.40%?0.01%),the moderate rate of semigranular cells about(35.22%?0.04%).By contrasting the dyeing time and dyeing effect of the two staining methods,Wright’s staining was more appropriate for the mysis haemocytes.When exposured in aquaculture water containing various concentration of V.alginolyticus,N.awatschensis began to die at 72 h while N.japonica at 48 h,and had a higher death rate than that of N.japonica in all the concentrations.Compared with N.japonica,N.awatschensis was less susceptible to V.alginolyticus, and the reason of such difference could be associated with the higher ratio of granular cells(including semigranular and granular cells)in N.awatschensis.

Abstract:The jumbo flying squid(Dosidicus gigas) is commercially important fishery species in the world.Assessment of population genetic diversity levels of jumbo flying squid is fundamental to the conservation and management of this species.The samples derived from the Chinese squid jigging vessel were collected from the eastern Pacific waters(81.9?-94.9?W,8.9?N-11.3?S)from July to October 2009.By using 724 bp fragment of mitochondrial cytochrome b gene(Cyt b),we analyzed the sequence variations and population genetic structures for 155 samples collected from seven sites of Peru and three sites of Costa Rica.In total,16 variable sites were acquired,and all of them were parsimony sites.43 haplotypes were identified from 155 individuals.Analysis of mtDNA Cyt b sequences of jumbo flying squids from the ten localities revealed that the mean haplotypic diversity was 0.873,while the nucleotide diversity was 0.003 69.6 haplotypes were shared by all the populations,while Peru population possessed the highest haplotypes(n=20).The AMOVA test of D.gigas revealed that 82.70% of the genetic variation occurred within populations.F_ST analysis suggested that significant genetic differentiations were found between the partial Peru populations and the Costa Rica populations,and even between partial Peru populations.However,no significant genetic differentiations were detected between Costa Rica populations.

Abstract:The prokaryotic expression vector pET28a/aiiO-AIO6 was constructed by inserting the aiiO-AIO6 gene into expression vector pET28a and transformed into E.coli.Subsequently,the recombinants with activity of N-acyl homoserine lactonase were investigated.After purification with nickel column,enzymatic characteristic of the target protein was researched.Moreover,the effects of purified enzyme solution on the expression of Hemolysin,Cytotonic enterotoxin,Extracellular protease,Serine protease, Phospholipase A1,ea tl five virulence factors from Aeromonas hydrophila ATCC7966 were detected by real-time quantitative PCR.The purified AiiO-AIO6 showed that the N-acyl-homoserine lactonase had optimal pH and temperature at pH 8.0 and 30 ℃,respectively.The enzyme was stable between pH 6.0 and 11.0,retained over 65% enzyme activity at 80 ℃ for 30 min.It resisted various neutral proteases and chemical reagents.The fusion protein can hydrolyze many N-acyl homoserine lactones substrates.With N-(3-oxo-octanoyl)-L-homoserine lactone as substrate,the K_m value of AiiO-AIO6 was 0.015 mmol/L and specific activity was 583.33 U/mg.The expression amount of five virulence factors of A.hydrophila had down-regulated trend obviously(P<0.05)at 8 h and 12 h.with adding the purified enzyme liquid for the expression amount of five virulence factors In this study the optimal pH and temperature of AiiO-AIO6 were obtained by detecting enzymatic property,and AiiO-AIO6 could inhibit A.hydrophila virulence factors expression indirectly by degrading signal molecules,which established a theoretical foundation for the application in aquaculture environment and biological control of pathogenic A.hydrophila.

Abstract:Asian clam(Corbicula fluminea)is a commercially important freshwater bivalve in South and East Asia.However,food clam mainly comes from the wild resources,and the natural populations have declined greatly and rapidly due to overfishing and natural habitats degradation.In China,the germplasm resource protection zone of C.fluminea has been set up in Hongze Lake to protect the natural resources.In this paper,genetic structure of four wild C.fluminea populations in Hongze Lake was analysized using ten polymorphic microsatellite DNA loci isolated and characterized by magnetic beads enrichment methods.The results showed that at least four of the loci were observed to have significant heterozygosity deficiency and obvious deviations from Hardy-Weinberg equilibrium(P<0.013)after Bonferroni correction in the four populations.Although values of expected heterozygosity were all above 0.752 and displayed high genetic diversity in the four populations,the level of genetic diversity fluctuated obviously.For example,the genetic diversity of the Jiangba and Linhuai populations was higher than that of the Gaoliangjian and Laozishan populations.The departure from mutation-drift equilibrium with partly heterozygote excesses was detected in all the C.fluminea populations under the IAM models and in Gaoliangjian population under the TPM models using Bottleneck software,which might indicate that the population structure has suffered bottleneck effects in the past,or was about to experience bottleneck effects,as well as the recent population fluctuation.AMOVA analysis across all populations and loci showed that there were the low levels of genetic divergences among the four populations(F_ST=0.017 7<0.05).1.77% of genetic variation was attributed to among populations.It suggested that all C.fluminea populations in Hongze Lake could be protected and managed as a single unit in genetic resource.All the study results would offer theoretical direction for the protection and utilization of the C.fluminea germplasm in Hongze Lake.

Abstract:The marine toxin yessotoxin(YTX)and its analogues have been detected in shellfish samples in Chinese coastal areas and they pose a potential threat to public health.Many YTXs toxicity studies have been carried out worldwide,but the process is still indeterminate.In order to study the toxicity of yessotoxin on Hela cells and analyze the possible action mechanism,MTT assay,optical microscope observation,Hoechst 33342 chromatin staining,DNA gel electrophoresis,rhodamine 123 staining,and calciumsensitive laser scanning confocal microscopy were conducted in this paper.The results demonstrated that YTX could induce a significant reduction of Hela cell viability and the cytotoxicity of the toxin was dosedependent.Meanwhile,the usual hallmarks of apoptosis could be detected,including chromatin condensation,DNA laddering,and loss of mitochondrial membrane potential.Furthermore,YTX caused cytosolic calcium levels to increase in Hela cells.The change of intracellular calcium concentration may be the main cause of cell apoptosis induced by YTX.

Abstract:Octopus variabilis has become one of the most popular seafood for its delicious taste,which has large market demand in China and is advantaged in marine products exports.However,due to the over fishing and water pollution,the natural resource of Octopus variabilis declined rapidly.For this reason,the industry of artificial culturing got rapid development.The Octopus variabilis will spurt the ink when meeting the stimulation originally.The peculiar ink defence system of Octopus variabilis is based on the activity of the highly specialized ink gland which is deputed to the continuous production of the black insoluble melanin pigment that is stored in the ink sac.This organ has been studied in other cephalopod,but the ink gland in Octopus variabilis is different from the others.Therefore,the histology of the ink sac and ultrastructural structure of the ink gland of Octopus variabilis was studied using light microscopy and electron microscopy in this paper.The observed results showed that the ink sac was composed of ink sac body,pipe and ink glands.The ink sac of Octopus variabilis opened into the end of the recta near the anus by pipe.The wall of the ink sac and pipe were both composed of epicardial,muscular layer,submucosa layer and mucosa layer.And the epicardial of ink sac wall were stratified squamous epithelium.The ink glands concentrated at the bottom of the ink sac,were formed by the hyperplasia of the mucasa epithelium to the cavity of the ink sac,shaped as rope with abundant connective tissue in the centre,there was cavity between branch of ink gland; Type A cells which can not secrete melanin and type B cells which can secrete melanin were observed.Microvillus were located in apex of the type B cells,and the ink particles adhered to the rough endoplasmic reticulum were formed in the melainin vesicles.The vesicles were released with exocytosit and cell disruption finally.

Abstract:Pepsin is a member of the large family of aspartic proteinases and plays a critical role in the digestion of food proteins.In the present study,three pepsinogens(PG-1,PG-2 and PG-3)were highly purified from the stomach of marine fish banded grouper(Epinephelus awoara)by ammonium sulfate fractionation and a series of column chromatographies.In the first anion exchange column DEAE-Sephacel,three peaks of hemoglobin-digesting activity were detected.These fractions were pooled respectively and applied to SP-Sepharose,DEAE-Sepharose or Sephacryl S-200 for further purification.As a result,4.0 mg of PG-1,12.2 mg of PG-2 and 4.4 mg of PG-3 were obtained with purification folds of 12.8,13.0 and 18.7,respectively.The molecular mass of the three purified pepsinogens was estimated to be 35,36 and 37 ku,respectively,by SDS-PAGE.Under acid conditions,pepsinogens converted into their active form pepsins(P-1,P-2 and P-3)with molecular masses of approximately 33,33 and 34 ku,respectively.PG-1 converted into its active form by a one-step pathway while PG-2 and PG-3 converted into their active forms by a stepwise pathway.NativePAGE analysis showed that all of the three purified pepsinogens reveal single band with different migration rates.The results indicated these three enzymes had different types of pepsinogens.To investigate the effect of pH or temperature on activity of pepsins,pepsinogens were first converted to pepsins at pH 2.0.They showed maximal activity at pH 3.0,2.5 and 2.5,respectively and the optimal temperatures of all PGs were 40 ℃,using acidic-denatured bovine hemoglobin as substrate.All of the enzymatic activity of the three pepsins decreased when the temperature is higher than 50 ℃,suggesting their susceptibility to higher temperature.The activity of all three pepsins could be completely inhibited by a typical aspartic proteinase inhibitor pepstatin A and these pepsins exhibited different sensitivities to pepstatin A.When the molar ratios of pepstatin A to pepsins(P-1,P-2 and P-3)were 8∶1,6∶1 and 4∶1,respectively,the enzymatic activities could be completely inhibited.These results strongly indicated that the three purified pepsins purified in the present study are aspartic proteinases.Western blot analysis revealed that these pepsinogens had different cross reaction with antisea bream PG-Ⅰ,PG-Ⅱ,PG-3b,PG-3a,PG-4a and PG-4b polyclonal antibodies.These results further confirmed that PG-1 and PG-2 were closely related pepsinogens and share high identity with each other,whereas PG-3 was different.The results of the kinetic constants of different pepsins were determined by Lineweaver-Burk plots using acidicdenatured bovine hemoglobin as substrate.The kinetic constants of K_m、k_cat and k_cat/K_m of pepsins(P-1,P-2 and P-3)for acidic-denatured bovine hemoglobin were 7.0?10^-5 mol/L,17.6 S^-1, 2.5?10⁵ mol/(L?S);5.5?10^-5 mol/L,22.8 S^-1,4.1?10⁵ mol/(L?S) and 5.2?10^-5 mol/L,18.7 S^-1, 3.6?10⁵ mol/(L?S),respectively.The specificity constant of P-2 was higher than those of the other two pepsins,suggesting that its catalytic efficiency is higher than those of the other two pepsins under physiological conditions.

Abstract:The Yangmeikeng artificial reef area is located in the eastern part of Daya Bay in Shenzhen.The artificial reefs were cast from March 20,2007,and the whole construction was finished on December 25 with the volume of 95.1 thousand m³ space and the area of 966 m?2 851 m.In order to know the biological distribution and the variation of the biomass density,six acoustic surveys were conducted with a split-beam echosounder(EY60 model,120kHz,Simrad)inside and outside the artificial reef area of Yangmeikeng in Daya Bay in different months from April 2007 to May 2009.The effective acoustic range is 122.54 n mile.Trawl samplings were used to help the acoustic assessment.In this paper,the volume backscattering strength(SV)data were integrated with 0.5n mile interval to analyze the distribution of biomass by using a fisheries acoustic software of Echoview(Myriax)combined with the historical data of ecology,resource characteristics and trawl data.The acoustic assessment results showed that the average biomass density inside and outside the artificial reef area were 41?10³ kg/n mile² and 28?10³ kg/n mile² respectively in survey 1,while 16?10³ kg/n mile² and 10?10³ kg/n mile² in survey 3,65?10³ kg/n mile² and 3?10³ kg/n mile² in survey 4,165?10³ kg/n mile² and 45?10³ kg/n mile² in survey 5.Obviously,the average density of biomass was higher inside the artificial reef area than the outside.And the inside biomass assumed the growth movement basically as time goes on.According to the trawl sampling data,the species estimated inside the artificial reef area were also increased evidently,such as Siganus canaliculatus and Nemipterus japonicus. It proved that the construction of artificial reefs in the Daya Bay could improve community structure of fishery resources.

Abstract:In this study,the IP-RPLC method for the determination of six ATP-related compounds(ATP,ADP,AMP,IMP,HxR,Hx)in aquatic product was established.The optimal conditions such as pH,flow rate and concentration of mobile phase were confirmed.The accuracy,precision and limit of quantitation were surveyed and evaluated.The method is based on an extraction of nucleotides from aquatic product with a solution of 10% perchloric acid followed by neutralization by the addition of KOH just prior to HPLC analysis.Chromatographic separations were performed using a Thermo ODS-2 Hypersil(250 mm?4.6 mm,5 μm)column,the column temperature was 25 ℃.The mobile phase consisted of 90% 0.05 mol/L sodium phosphate buffer,10% methanol and 9.5 mmol/L tetrabutylammonium hydroxide,and was adjusted to pH 6.5 with phosphoric acid,the mobile phase was delivered at a flow rate of 0.9 mL/min with equivalent elution,and the detection wave length was 254 nm.The six ATP-related compounds were separated in 13 min.The standard curves of six ATP-related compounds were linear within a range of 2-400 μg/mL,and the correlation coefficient deviations range from 0.999 4 to 1.000 0.The limits of detection(S/N=3)were between 0.1 μg/mL and 0.4 μg/mL.The average recovery of spiked sample deviations range from 82.2% to 110.0%,and the relative standard deviations(RSD)were between 4.2% and 9.5%.In conclusion,the method proved to be simple,rapid,reliableand with high accuracy and precision.The method has practical value for detecting six ATP-related compounds in aquatic product.

Abstract:Artificial reefs(ARs),constructed with reinforced concrete,have been deployed along many coasts to enhance fisheries aquaculture and diving tourism,protect habitats,and foster research all over the world for a few years.Though new techniques and developments were applied to ARs,unexpected problems have also occurred in deployment processes,stability,local scours,durability of materials,and design characteristics.Of these problems,the stability of ARs is a very important issue in preventing the failure of reef units due to wave and current action.It is indicated that the principal hydrographic factors to be considered in AR construction consist of installation depth,reef weight,wave height,currents,and tides.In this study,the authors analyzed stability of an cube artificial reef to determine safe weight and deployment depth at varying water depths(6-20 m)and bottom slopes(10^-1,30^-1,50^-1)based on wave theory.FLUENT software and physics equations were used to estimate drag coefficients and waves forces.Drag coefficients for the reef is 1.5.Deep water offshore wave conditions in Daya Bay were transformed into shallow nearshore waters representative of the artificial reef site using linear wave theory.Four wave conditions were used in this study,including typhoon wave and different return period wave(10-year,25-year,50-year).The results showed that the safe weights fluctuated with water depths,increased first and then decreased when wave broke.Under typhoon wave,the maximum values of safe weights were 21.4,16.8 and 14.2 t for 3 bottom slopes,which occurred at water depths of 6,7 and 7 m respectively.When wave height and period were increased,safe weight and corresponding water depth were increasing at the same time.The maximum values of safe weights were 42.4,22.4 and 20.3 t,which occurred at water depths of 10,12 and 14 m respectively under wave of 25-year return period.Bottom slope was closely related to safe weight.When bottom slopes were investigated for the same wave parameters and depths,safe weights decreased and vice versa when slopes increased.The distinction was much more evident between a bottom slope of 10^-1 and the other bottom slopes(30^-1,50^-1).The maximum value of safe weight for 10^-1 could be 2.2 times the safe weight for 50^-1 at the same water depth under wave of 25-year return period.The flat seabed is more proper for ARs deployment.It is concluded that safe weight design must take wave parameters,water depths and bottom slopes into consideration,and improper water depth or slopes might cause the failure of reef units.To prevent navigational hazards and loss of stability,the investigated reef was suggested to deploy at a water depth of 12 m or deeper with a design weight of 22.4 t in Daya Bay.The design weight and selected deployment depth can resist wave force of 25-year return period and satisfy the ARs engineering project requirement of safety.

Abstract:Pearls are known as “the queen of gems”.The improvement of the cultured pearls quality is the focus of pearl industry and the important topic in the research field of pearls.In this paper we summarized the standard of evaluating the quality of cultured pearls in six aspects,including color,size,shape,lustre,surface finish and nacre thickness of nucleated pearls.The major species of pearl oysters and mussels were introduced as well as the characteristics of freshwater pearls and nucleated seawater pearls they produced.The relation between the sizes,the shell colors of the pearl oysters and mussels and the pearl quality was discussed.In this paper,we emphatically introduced the influences of the species,ages and shell colors of donors oysters and mussels,which were used to prepare mantle transplantation(allograft),on the pearl quality.And the influences of the chemicals factors,the means of separating mantle transplantation(allograft)and the number of the mantle transplantations during the implantation of mantle transplantation on the pearl quality are also introduced.How the culture conditions influenced the pearl quality was discussed in addition,and the culture conditions included water quality and microelements,water depth,culture pattern and period to culture the pearl oysters and mussels.

Abstract:The characteristics of the improved strain SF-2 were evaluated and compared with the improved variety SF-1 and the wild type of Porphyra haitanensis according to the results of the laboratory studies and pilot scale tests in mariculture farm.There were significant differences between SF-2 and WT in growth rates,contents of phycobiliprotein,thicknesses of the blades and yields of pilot cultivation.The absolute growth rates of SF-2 blades were significantly higher than those of WT.The length of 90-day-old SF-2 blades was(391.6?47.37) cm which was about 10 times longer than WT.There were five peaks in the in vivo absorption spectra of SF-1,SF-2 and WT blades between wavelengths of 350-750 nm,and the peak values of SF-1 and SF-2 were almost the same,but both higher than those of WT.The phycobiliprotein content of SF-2 blades was (90.81?3.98) mg/g which was slightly higher than SF-1 and was 1.95 times higher than that of WT.The mean thickness of SF-2 blades was(31.95?4.16) μm,which was 14.0% and 38.7% thinner than that of SF-1 and WT,respectively.The number of the released conchospores per shell of SF-2 conchocelis in mariculture farm was 286 000,which was 43.0% more than that of that of SF-1 and was sufficient in cultivation.The fresh yield of SF-2 of the first four harvests was 240 000 kg,which increased by 30.1% compared with WT and by 6.7% compared with SF-1,resepectively.It came to a conclusion that the superiority of the improved strain SF-2 possesses the value to be applied and disseminated.

Abstract:The differences of muscle in nutritional components,delicious materials and physical characteristics of farmed fugu, Takifugu rubripes from Dalian,Hebei and Dandong,were tested and analyzed in order to evaluate its nutritive value and flesh quality.The three groups represented three culture models.The results showed that the content of crude protein was about 85% of dry matter and the content of crude fat was lower than 2% dry matter.There were no significant differences in the contents of moisture and crude protein,crude lipid among the three series fugu.18 common amino acids were found in the flesh,and amount of which was 15.75% of wet matter or 79.13%-83.19% of dry matter.The content of essential amino acids and nonessential amino acids was 32.77%-33.68% and 39.06%-41.72%,respectively.Glutamic acid was the most one in all amino acids,and its content was up to 12%.The delicious amino acids including Glu,Gly,Ala and Asp in Dandong group were up to 32.09%,higher than those of Dalian group(29.94%)and Hebei group(29.90%)significantly(P<0.05).There were also differences in some fatty acids,such as C16∶0,C20∶1ω9,C22∶6ω3,and total saturated fatty acids(SFA).The results of nucleotide and its metabolites indicated that hypoxanthine nucleotide(IMP)was the highest metabolite of nucleotide,whose content was up to 220.75-265.03 mg/L,being 10-100 times as much as the others.The K value of HB group(6.36)was lower than DD(10.65)and DL(12.06),suggesting that it had a longer shelf life than DD and DL groups.The results of texture using texture analyzer SMS TA XT plus indicated that there was no difference except the hardness and chewiness of muscle among the three models.The hardness of HB and DD was higher than that of DL significantly(P<0.05).In conclusion,the pattern of amino acids,the high content of essential amino acids(EAA)and poly-unsaturated fatty acids(PUFA)and DHA indicated that fugu flesh was nutritional and healthy to human,and was a good species for development.Different culture model influenced the flesh quality,and the combination of pond culture and net cage culture in sea was a good model.

Abstract:A 6-week feeding experiment was conducted to determine the optimum feeding frequency for gastric evacuation,growth performance and body composition of the juvenile genetic improved farmed tilapia strain of Nile Tilapia(Oreochromis niloticus)(GIFT strain of Nile tilapia).At the start of the feeding trial,gastric evacuation rate of the fish was monitored after feeding to visual satiety.Gastric evacuation of the fish was best fitted with square root model.It was estimated that gastric feed contents gradually decreased and reached the pre-feeding level within 15 h and 80% evacuation would require 9 h,which suggested corresponded to the return of appetite.Six replicate groups of the 360 fish(initial weight 3.72 g)were fed to visual satiety puffed feed at different feeding frequencies(four meals a day,three meals a day,two meals a day,four meals every 2 days,three meals every 2 days and two meals every 2 days).As feeding frequency decreased,the weight gain and feed efficiency of the juvenile gradually decreased.The specific growth ratios(SGR)of fish fed four meals a day,three meals a day and two meals a day were significantly higher than those of four meals every 2 days,three meals every 2 days and two meals every 2 days(P<0.05).The feed intakes of fish fed two meals a day,four meals every 2 days,three meals every 2 days and two meals every two days were significantly lower than those of three meals a day and four meals a day(P<0.05).As feeding frequency decreased,moisture contents of fish body increased and the contents of fat and protein decreased gradually,and there were significant difference between the fish fed four meals a day,three meals a day and the fish fed two meals every 2 days.Hepatosomatic indices of fish were not significantly different between all test groups.It is concluded that two meals a day is more effective than other feeding frequencies for improving growth performance or feed efficiency of juvenile GIFT strain of Nile tilapia from 3.7 to 48.0 g.Gastric evacuation is a simple and convenient method to evaluate optimum feeding frequency of juvenile GIFT strain of Nile tilapia.

Abstract:Full cDNA sequence of a secretory IgM(sIgM)gene in largefin longbarbel catfish(Mystus macropterus Bleeker)was cloned using RACE-PCR and RT-PCR methods.It has 1 992 nucleotides,including 5′UTR of 53 nucleotides,3′UTR of 226 nucleotides and an open reading frame with 1 713 nucleotides encoding a 570 amino acid peptide.The deduced amino acid sequence in M.macropterus contains 4 constant regions(CH)and a variable domain(VH)which consists of 4 frame regions (FRs)and 3 complementary determining regions(CDRs).The IgM comparison in seven teleost species showed that IgM in M. macropterus shared the highest identity(54.3%)with that in Ictalurus punctatus, and the lowest identity(24.6%)with that in Epinephelus coioides, and that the conserved cysteines and tryptophans existed in all fishes involved.Phylogenetic tree based on some teleost Ig heavy chain amino acids suggested IgM in M.macropterus was clustered closely with that of I.punctatus. Fluorescent real-time PCR showed that IgM mRNA expression of M. macropterus was mainly detected in blood cells,spleen,kidney and head kidney,and increased significantly in blood cells,spleen,head kidney between day 1 and day 10 after injection of Aeromonas hydrophila.

Abstract:Double GCRV outer capsid protein VP7 genes(0.9 kb)and β-actin promoter(0.56 kb)from Megalobrama amblycephala were amplified and cloned into gene transfer vector pFastBac^TM Dual to obtain recombinant pFastBac-β-VP7-1-VP7-2.Immune experiment and immunological effect were studied.The recombinant plasmids were divided into three groups based on doses:10,30,60 μg.30 μg pFastBac^TM Dual group and control group were designed in addition.Immune efficacy was determined by means of transcriptions of VP7,antibody detection by indirect agglutination reaction and challenge experiment on the 14th,21st,28th,and 49th days after immunization.The results showed that pFastBac-β-VP7-1-VP7-2 was transformed into body cell,VP7 gene could be controlled for expression constantly by β-actin promoter,and transcription of VP7 was still in process on the 49th day.Antibody was produced and the titers reached their peak on the 21th day after immunization.The mortality rates were 0%,0% and 5% respectively in 10 μg,30 μg and 60 μg vaccine immunization groups,30% in pFastBac^TM Dual group,and 100% in control group after GCRV injection.All results suggested that pFastBac-β-VP7-1-VP7-2 had good immuno-protective efficacy as DNA vaccine against GCRV.Therefore,the study provided important academic basis for research,development and application of the GCRV genetic vaccine.