Morphological comparison and gonadotropins cell localization of mature female turbot and mouse pituitary

Reproduction is subtlety regulated by the hypothalamic-pituitary-gonad(HPG)axis in vertebrates.Pituitary gland is the center of the HPG axis,while pituitary gonadotropins follicle stimulating hormone(FSH)and luteinizing hormone(LH)were identified the key elements of the HPG axis in teleost and mammal.Morphology,cell lines,and gonadotropins cell localization of female turbot and mouse pituitary were determined at mature stage to illustrate the anatomical difference and cell characteristics in this study.Results show that turbot pituitary is chicken heart-shaped,dorsoventral,located on the ventral surface of the diencephalon.The mouse pituitary is oval,located in the pituitary fossa of the sella turcica at the skull base.Two well-distinguished areas adenohypophysis(AH)and neurohypophysis(NH)in pituitary were identified in turbot and mouse.Turbot AH comprised the rostral pars distalis(RPD),proximal pars distalis(PPD),and pars intermedia(PI).NH was not pronounced and with finger-like protrusions into PPD.However,mouse AH only comprised the pars distalis(PD)and PI.NH distribution was semicircular.Three main types of cells(acidophilic,basophilic,and chromophobic cells)were distributed in the mouse PD region,whereas appeared in the turbot PPD,RPD,and PI.Moreover,the percentage of mouse chromophobic and basophilic cells was higher and lower than that of turbot,respectively.The diameter of the aforementioned three cells in the mouse was significantly higher than turbot.fshβ-and lhβ-immunoreactive signals were identified in turbot-distinct pituitary cells that primarily occupied the peripheral and central regions of AH.However,mouse fsh-and lh-immunoreactive cells were expressed in the same cells and present in the PD.These results demonstrate the significantly difference of pituitary morphology,cell lines and gonadotropins(fshβand lhβ)location in female turbot and mouse.These differences help for fully understand the evolution and endocrinological functions of pituitary.

The ontogeny of acidic digestive tract in larval turbot Scophthalmus maximus based on H+/K+-ATPase and pepsinogen

Acidic digestion is an important digestive process of marine fish.In fish stomach,two enzymes are involved in the secretion of hydrochloric acid(HCl)and proteomic digestion:H^(+)/K^(+)-ATPase and pepsinogen.However,the starting of digestive function in fish is still unclear.To reveal the details of acidic digestion of turbot Scophthalmus maximus in early development,a 40 day of turbot larvae culture was conducted.The H^(+)/K^(+)-ATPase gene from the turbot S.maximus(smH^(+)/K^(+)-ATPase)was identified and characterized.Based on our previous discription on pepsinogen of turbot S.maximus,we combined pepsinogen and H^(+)/K^(+)-ATPase and analyzed the mechanism of acidic digestion in turbot.Results show that the spatial and temporal expression profiles of H^(+)/K^(+)-ATPase agreed with pepsinogen A and C in turbot,indicating a synergetic action between H^(+)/K^(+)-ATPase and pepsinogen during the acidic digestion process.In addition,the turbot juveniles showed a faster growth after the expressions of H^(+)/K^(+)-ATPase gene and pepsinogen gene,demonstrating that pepsin had a higher digestive efficiency,for which a compound diet should be provided to the fish from Day 22 onward.This study provided a reference for biology research and aquaculture of turbot and other marine fishes.

Developmental quantitative genetic analysis of body weights and morphological traits in the turbot, Scophthalmus maximus

In order to elucidate the genetic mechanism of growth traits in turbot during ontogeny, developmental genetic analysis of the body weights, total lengths, standard lengths and body heights of turbots was conducted by mixed genetic models with additive-dominance effects, based on complete diallel crosses with four different strains of Scophthalmus maximus from Denmark, Norway, Britain, and France. Unconditional genetic analysis revealed that the unconditional additive effects for the four traits were more significant than unconditional dominance effects, meanwhile, the alternative expressions were also observed between the additive and dominant effects for body weights, total lengths and standard lengths. Conditional analysis showed that the developmental periods with active gene expression for body weights, total lengths, standard lengths and body heights were 15–18, 15 and 21–24, 15 and 24, and 21 and 27 months of age, respectively. The proportions of unconditional/conditional variances indicated that the narrow-sense heritabilities of body weights, total lengths and standard lengths were all increased systematically. The accumulative effects of genes controlling the four quantitative traits were mainly additive effects, suggesting that the selection is more efficient for the genetic improvement of turbots. The conditional genetic procedure is a useful tool to understand the expression of genes controlling developmental quantitative traits at a specific developmental period（t-1→t） during ontogeny. It is also important to determine the appropriate developmental period（t-1→t） for trait measurement in developmental quantitative genetic analysis in fish.

Effects of Dietary Stachyose on Growth Performance, Digestive Enzyme Activities and Intestinal Morphology of Juvenile Turbot(Scophthalmus maximus L)

A 12-week feeding trial was conducted to evaluate the effects of dietary stachyose on the growth performance, digestive enzymes activities and intestinal structures of juvenile turbot(Scophthalmus maximus L). Five isonitrogenous(49.58% crude protein) and isolipidic(10.50% crude lipid) diets were formulated to contain 0(Control), 0.625%(S-0.625), 1.25%(S-1.25), 2.5%(S-2.5) and 5%(S-5) stachyose, respectively. With the increase of stachyose level, the growth performance and feed utilization of turbot, such as the specific growth rate, final mean body weight, weight gain rate and feed efficiency, increased significantly(P < 0.05) and then stabilized. The feed intake of fish fed S-5 was significantly higher(P < 0.05) than that of fish in other groups. The activities of trypsin, intestinal caseinolytic, stomach and intestinal amylase were significantly influenced by stachyose(P < 0.05). The highest values of trypsin and intestinal caseinolytic activities were observed in group S-1.25, while the highest activity of stomach amylase and the lowest activity of intestine amylase were observed in group S-5. No lesion or damage was found on the distal intestine structures of fish from all treatments, while the height of simple folds in the distal intestine was significantly increased(P< 0.05) when 1.25% or 2.5% stachyose was added in the diets. These results indicated that moderate level of stachyose(1.25%) improves the growth performance, feed utilization, digestive enzyme activities and the distal intestine structures of juvenile turbot.

Effects of temperature, pH and NaCl on protease activity in digestive tract of young turbot, Scophthalmus maximus

The protease activity in digestive tract of young turbot Scophthalmus maximum was studied, and the optimal pH, temperature and NaCl concentration were determined for different portions of the fish’s internal organs. The optimal activity in the fish’s stomach was at pH of 2.2, while that in the intes- tinal extracts was within the alkaline range from 9.5 to 10.0. In hepatopancreas, the optimal pH was in low alkalinity at 8.5. The optimal reaction temperature was above 40℃ in stomach, intestine and hepato- pancreas. With increasing temperature, the pH value increased in stomach, while in the intestine, an op- posite tendency was observed due to combined effect of pH and temperature. NaCl concentration showed inhibitory impact on protein digestion in hepatopancreas. The main protease for protein digestion in turbot seemed to be pepsin. Moreover, the maximum protease activity in different segments of intestine existed in the hindgut.

Isolation and characterization of 45 polymorphic microsatellite loci of turbot(Scophthalmus maximus)and cross-species amplification

Turbot （Scophthalmus maximus） is a flatfish species commercially important for aquaculture. In this study, we generated a microsatellite-enriched genomic DNA library for Scophthalmus rnaxirnus, and then isolated and characterized 45 microsateIIite loci by genotyping 30 individuals. The observed number of alleles ranged from 2 to 19 with an average of 6.24, while the effective number of alleles ranged from 1.30 to 11.11 with an average of 3.66. The expected heterozygosities varied from 0.235 to 0.9254 and polymorphic information content ranged from 0.204 4 to 0.903 3, with an average of 0.622. Twelve loci deviated significantly from Hardy-Weinberg equilibrium, and no significant linkage disequilibrium was observed between any pair of loci after Bonferroni correction. In cross-species amplification, five flatfish species （Paralichthys lethostigma, Verasper rnoseri, platichthys stellatus, Hippoglossoides dubius and Cynoglossus semilaevis） showed at least one polymorphic locus. These polymorphic microsatellite loci should prove useful for population analysis of turbot and other related species.

Effect of stocking density on performances of juvenile turbot (Scophthalmus maximus) in recirculating aquaculture systems

Limited information has been available about the influence of loading density on the performances of Scophthalmus maximus, especially in recirculating aquaculture systems （RAS）. In this study, turbot （13.84±2.74 g; average weigh±SD） were reared at four different initial densities （low 0.66, medium 1.26, sub-high 2.56, high 4.00 kg/m^2） for 10 weeks in RAS at 23±1℃ Final densities were 4.67, 7.25, 14.16, and 17.47 kg/m^2, respectively, which translate to 82, 108, 214, and 282 percent coverage of the tank bottom. Density had both negative and independent impacts on growth. The final mean weight, specific growth rate （SGR）, and voluntary feed intake significantly decreased and the coefficient of variation （CV） of final body weight increased with increase in stocking density. The medium and sub-high density groups did not differ significantly in SGR, mean weight, CV, food conversion rate （FCR）, feed intake, blood parameters, and digestive enzymes. The protease activities of the digestive tract at pH 7, 8.5, 9, and 10 were significantly higher for the highest density group, but tended to be lower （not significantly） at pH 4 and 8.5 for the lowest density group. The intensity of protease activity was inversely related to feed intake at the different densities. Catalase activity was higher （but not significantly） at the highest density, perhaps because high density started to induce an oxidative effect in turbot. In conclusion, turbot can be cultured in RAS at a density of less than 17.47 kg/m^2. With good water quality and no feed limitation, initial density between 1.26 and 2.56 kg/m^2 （final： 7.25 and 14.16 kg/m^2） would not negatively affect the turbot cultured in RAS. For culture at higher density, multi-level feeding devices are suggested to ease feeding competition.

Estimation of genetic parameters for upper thermal tolerance and growth-related traits in turbot Scophthalmus maximus using the Bayesian method based on Gibbs sampling

In order to carry out the genetic improvement of turbot upper thermal tolerance, it is necessary to estimate the genetic parameters of UTT（upper thermal tolerance） and growth-related traits. The objective of this study was to estimate genetic parameters for BW（body weight） and UTT in a two-generational turbot（Scophthalmus maximus L.） pedigree derived from four imported turbot stocks（England, France, Denmark and Norway）. A total of 42 families including 20 families from G1 generation and 22 families from G2 generation were used to test upper thermal tolerance（40–50 animals per family） in this study and the body weight of individuals were measured. The heritability of BW and UTT and the correlation between these two traits were estimated based on an individual animal model using Bayesian method based on two types of animal models with and without maternal effects.These results showed that the heritabilities for BW and UTT and phenotypic and genetic correlations between the two traits estimated from model without maternal effects were 0.239±0.141, 0.111±0.080, 0.075±0.026 and–0.019±0.011, respectively. The corresponding values from model with maternal effects were 0.203±0.115,0.055±0.026, 0.047±0.034 and –0.024±0.028, respectively. The maternal effects of BW and UTT were 0.050±0.017 and 0.013±0.004, respectively. The maternal effects had a certain influence on the genetic evaluation of the two traits. The findings of this paper provided the necessary background to determine the best selection strategy to be adopted in the genetic improvement program.

The eco-nutrition requirements for dietary protein and its rhomb characteristics in juvenile turbot (Scophthalmus maximus L.)

We evaluated the dietary protein requirements of juvenile turbot (Scophthalmus maximus L.) and their effects on aquatic quality. Five experimental diets were formulated containing 450, 480, 500, 520, and 540 g/kg. Each diet was randomly assigned to triplicate groups of juvenile turbot (mean initial body weight 34.5 ± 5.5 g) for 88 d. Both the weight gain ratio and feed efficiency increased with increasing dietary protein up to 500 g/kg, but no further improvement was detected when dietary protein levels were >500 g/kg. Protein intake and digestion increased with protein levels, while fecal nitrogen and nitrogen content in seawater increased only when dietary protein exceeded 500 g/kg. Protein digestibility was highest at intermediate dietary protein levels. Chemical oxygen demand, nitrite-nitrogen (NO2--N) and phosphatic-phosphor (PO43--P) levels increased in the rearing water as dietary protein levels increased. The optimum eco-nutrition level of dietary protein for juvenile turbot was 500 g/kg under the current experimental conditions. The diets containing 540 and 500 g/kg protein had similar growth rates and feed conversion ratios, but levels of ammonia (NH4+) and nitrogen were considerably higher in the water and feces, respectively, at the higher level of dietary protein. The difference in the pattern of change between body weight gain and ammonia concentration in water with increasing dietary protein is described by rhomb characteristics.

Proline with or without Hydroxyproline Influences Collagen Concentration and Regulates Prolyl 4-Hydroxylase α(I) Gene Expression in Juvenile Turbot(Scophthalmus maximus L.)

This study was conducted to investigate the effect of dietary proline(Pro), and Pro and hydroxyproline(Hyp) in combination on the growth performance, total Hyp and collagen concentrations of tissues, and prolyl 4-hydroxylase α(I)(P4H α(I)) gene expression in juvenile turbot feeding high plant protein diets. A diet containing 50% crude protein and 12% crude lipid was formulated as the basal and control, on which other two protein and lipid contents identical experimental diets were formulated by supplementing the basal with either 0.75% Pro(Pro-0.75) or 0.75% Pro and 0.75% Hyp(Pro+Hyp). Four groups of fish in indoor seawater recirculating systems, 35 individuals each, were fed twice a day to apparent satiation for 10 weeks. The results showed that dietary Pro and Hyp supplementation had no significant effect on growth performance and feed utilization of juvenile turbot(P > 0.05). Total Hyp and collagen concentrations in muscle were significantly increased when dietary Pro and Hyp increased(P < 0.05), and fish fed diet Pro+Hyp showed significantly higher free Hyp content in plasma than those fed other diets(P < 0.05). The expression of P4 H α(I) gene in liver and muscle was significantly up regulated in fish fed diet Pro-0.75 in comparison with control(P < 0.05); however the gene was significantly down regulated in fish fed diet Pro+Hyp in muscle in comparison with fish fed diet Pro-0.75(P < 0.05). It can be concluded that supplement of crystal L-Pro and L-Hyp to high plant protein diets did not show positive effects on growth performance of juvenile turbot, but enhanced total collagen concentrations in muscle.

Impact assessment of modified clay on embryo-larval stages of turbot Scophthalmus maximus L.

Using modified clay is one of the most promising methods for the mitigation of harmful algal blooms(HABs).However,the environmental impact of modified clay has become a subject of global concern.In this study,turbot(Scophthalmus maximus L.)embryos were used as a model to assess the effect of modified clay on this sensitive stage of fish development.Results show that the 24 and 48h LC 50(median lethal concentrations)of the modified clay were 1.70 and 1.65 g/L,and the safe concentration was 0.47 g/L,which is much higher than the concentration used to treat HAB.The modified clay did not affect significantly the hatchability of turbot embryos but when the concentration exceeded 0.50 g/L,the deformity rate of newly hatched larvae increased significantly.The total length,specific growth rate(SGR)and yolk sac absorption rate of larvae reached their peaks at 0.50 g/L and then gradually decreased as the concentration of modified clay increased.Therefore,a moderate amount of modified clay does not harm the survival and hatching of turbot embryos,or the growth and development of newly hatched larvae.

Studies on the edwardsiellosis and characterization of pathogenic bacteria from diseased flounder (Paralichthys olivaceus L.) and turbot (Scophthalmus maximus L.)

Edwardsiellosis of flounder and turbot occurring in different mariculture farms during 2001～ 2004 was examined, including the conditions of disease occurrence, clinical signs and pathological changes. The results showed that all diseased fishes expressed bacterial septicaemia. A total of 148 strains were identified using a combination of traditional physiological and biochemical tests and partial 16S rRNA gene analysis. In addition, the mole fraction G ＋ C ratio of the DNA of representative strain of isolates and serum homology were detected, and pathogenicity tests of isolates were conducted by experimental infection. The results revealed that 148 strains were identified as E. tarda of genus Edwardsiella, all the isolates are of serologic similarity, and have strong pathogenicity to flounder and turbot.

Expression Pattern of Peptide and Amino Acid Genes in Digestive Tract of Transporter Juvenile Turbot(Scophthalmus maximus L.)

Turbot(Scophthalmus maximus L.),a carnivorous fish species with high dietary protein requirement,was chosen to examine the expression pattern of peptide and amino acid transporter genes along its digestive tract which was divided into six segments including stomach,pyloric caeca,rectum,and three equal parts of the remainder of the intestine.The results showed that the expression of two peptide and eleven amino acid transporters genes exhibited distinct patterns.Peptide transporter 1(Pep T1) was rich in proximal intestine while peptide transporter 2(PepT2) was abundant in distal intestine.A number of neutral and cationic amino acid transporters expressed richly in whole intestine including B^0-type amino acid transporter 1(B^0AT1),L-type amino acid transporter 2(LAT2),T-type amino acid transporter 1(TAT1),proton-coupled amino acid transporter 1(PAT1),y^+L-type amino acid transporter 1(y^+LAT1),and cationic amino acid transporter 2(CAT2) while ASC amino acid transporter 2(ASCT2),sodium-coupled neutral amino acid transporter 2(SNAT2),and y^+L-type amino acid transporter 2(y^+LAT2) abundantly expressed in stomach.In addition,system b^(0,+) transporters(rBAT and b^(0,+)AT) existed richly in distal intestine.These findings comprehensively characterized the distribution of solute carrier family proteins,which revealed the relative importance of peptide and amino acid absorption through luminal membrane.Our findings are helpful to understand the mechanism of the utilization of dietary protein in fish with a short digestive tract.

Interaction of temperature and salinity on the expression of immunity factors in different tissues of juvenile turbot Scophthalmus maximus based on response surface methodology

Central Composite Design(CCD) and response surface methodology were used in the experiment to examine the combined effect of temperature(16-28℃) and salinity(18-42) on Hsp70 and IgM genes expression levels in turbot(Scophthalmus maximus) liver and kidney.The results showed that the coefficients of determination(R^2=0.965 2 for liver Hsp70,0.972 9 for kidney Hsp70,0.921 for liver IgM and 0.962 1 for kidney IgM) and probability values(P<0.01) were significant for the regression model.The interactive effect between temperature and salinity on liver Hsp70,kidney Hsp70 and liver IgM were not significant(P>0.05),while the interactive effect between temperature and salinity on kidney IgM was significant(P<0.01).The model equation could be used in practice for forecasting Hsp70 and IgM genes expression levels in the liver and kidney of juvenile turbot via applying statistical optimization of the response of interest,at which the maximum liver Hsp70,kidney Hsp70,liver IgM and kidney IgM of1.48,1.49,2.48,and 1.38,respectively,were reached.The present model may be valuable in assessing the feasibility of turbot farming at different geographic locations and,furthermore,could be a useful reference for scientists studying the immunity of turbot.

Distribution and ultrastructure of pigment cells in the skins of normal and albino adult turbot, Scophthalmus Maximus

The distribution and ultrastructure of pigment cells in skins of normal and albino adult turbots were examined with transmission electron microscopy （TEM）. Three types of pigment cells of melanophore, iridophore and xanthophore have been recognized in adult turbot skins. The skin color depends mainly on the amount and distribution of melanophore and iridophore, as xanthophore is quite rare. No pigment cells can be found in the epidermis of the skins. In the pigmented ocular skin of the turbot, melanophore and iridophore are usually co-localized in the dermis. This is quite different from the distribution in larvae skin. In albino and white blind skins of adult turbots, however, only iridophore monolayer still exists, while the melanophore monolayer disappears. This cytological evidence explains why the albino adult turbot, unlike its larvae, could never resume its body color no matter what enviroumental and nutritional conditions were provided. Endocytosis is quite active in the cellular membrane of the iridophore. This might be related to the formation of reflective platelet and stability of the iridophore.

Characterization and differential expression of three GnRH forms during reproductive development in cultured turbot Schophthalmus maximus

Turbots( Schophthalmus maximus), one of the most important economic marine flatfish species, fail to undergo final spawning and spermiation naturally under artificial farming conditions. In vertebrates, reproduction is regulated by the brain-pituitary-gonadal axis(BPG-axis), and gonadotropin releasing hormone(GnRH) is one of its key components. Therefore, to better understand the physiology of reproduction in the turbot, three of the genes encoding GnRH subtypes— sbGnRH, c GnRH-II and sGnRH —were cloned and sequenced by isolating the cDNA sequences. The localizations and patterns of expression of their mRNAs were also evaluated during seasonal gonadal development. All three mRNAs were expressed abundantly in the brain; sbGnRH and sGnRH mRNAs were also detected in the gonads and pituitary gland, and sbGnRH expression was much higher than that of sGnRH, indicating the critical role of sbGnRH in regulating the BPG-axis. Moreover, the brain expression patterns of sbGnRH and sGnRH mRNAs showed an increased trend during gonadal development, peaking in mature stages. This indicated the direct regulation of gonadal development by the GnRH system. In addition, c GnRH-II mRNA expression showed no significant variations, suggesting that c GnRH-II is not critically involved in the control of reproduction. Further, the mRNA abundances of the three GnRH forms in the breeding season were significantly higher than those in immature and post-breeding stages in all analyzed brain areas. Therefore, we propose that sbGnRH is the most important hormone for the regulation of reproduction in turbot via the BPG-axis. These results will help in better understanding the reproductive endocrine mechanisms of turbots and lay the groundwork for additional studies aimed at comparing the reproductive physiology of wild individuals with those raised under artificial conditions.

Effect of Dietary Vitamin E on the Sperm Quality of Turbot(Scophthalmus maximus)

A 3-month feeding experiment was conducted in an in-door seawater system to investigate the effect of dietary vitamin E （Ve） on the sperm quality of turbot （Scophthalmus maximus）. D-α-tocopherol acetate was supplemented to the basal （control） diet （65.14 mg kg-l Ve） to obtain low and high levels of dietary Ve （244.60 mgkg-1, LVe; 721.60 mg kg-1, HVe）. Compared with the con- trol, sperm concentration was significantly increased in Ve-supplemented groups （LVe and HVe）; while relative sperm volume and testis-somatic index were significantly increased in group HVe only. Sperm motility duration was significantly longer in group HVe than in the control, but no significant difference was observed in percent motility among groups. Sperm size, the uniformity of mito- chondrial size, and the integrity of mitochondria cristae and plasma membrane were improved by dietary Ve, especially in HVe. The content of Ve in testis and liver as well as polyunsaturated fatty acids in sperm increased with dietary Ve. These results suggested that dietary Ve, especially at the high level （721.60 mg kgl）, significantly improved sperm concentration and motility duration and main- tained normal sperm morphology of turbot.Abstract A 3-month feeding experiment was conducted in an in-door seawater system to investigate the effect of dietary vitamin E （Ve） on the sperm quality of turbot （Scophthalmus maximus）. D-α-tocopherol acetate was supplemented to the basal （control） diet （65.14 mg kg-l Ve） to obtain low and high levels of dietary Ve （244.60 mgkg-1, LVe; 721.60 mg kg-1, HVe）. Compared with the con- trol, sperm concentration was significantly increased in Ve-supplemented groups （LVe and HVe）; while relative sperm volume and testis-somatic index were significantly increased in group HVe only. Sperm motility duration was significantly longer in group HVe than in the control, but no significant difference was observed in percent motility among groups. Sperm size, the uniformity of mito- chondrial size, and the integrity of mitochondria cristae and plasma membrane were improved by dietary Ve, especially in HVe. The content of Ve in testis and liver as well as polyunsaturated fatty acids in sperm increased with dietary Ve. These results suggested that dietary Ve, especially at the high level （721.60 mg kgl）, significantly improved sperm concentration and motility duration and main- tained normal sperm morphology of turbot.

Administration of Yeast Glucan on Immunity of Offspring in Turbot Scophthalmus maximus: A Trans-Generational Immune-Enhancing Effect

β-glucan has been shown to increase immunity and survival in various juvenile and adult fish both in freshwater and marine aquaculture species as well as in marine fish larvae. However, information about the trans-generational immune-enhancing effects of β-glucan remains rather limited. Here we clearly show that dietary intake of β-glucan enhanced the levels of C3, Bf and lysozyme in the serum of turbot as well as in their eggs released. We also show that yeast glucan induced a significant increase in lysozyme activity in both the serum and eggs. Moreover, the embryos derived from yeast glucan-treated turbot were more resistant to bacterial challenge than control embryos. By contrast, the administration of yeast glucan on female turbots had little influence on the egg development and embryonic development. Collectively, these data indicate that yeast glucan can be safely used to promote the non-specific trans-generational immunity in offspring of turbot.

Estimation of genetic parameters for growth trait of turbot using Bayesian and REML approaches

Bayesian and restricted maximum likelihood （REML） approaches were used to estimate the genetic parameters in a cultured turbot Scophthalmus maximus stock. The data set consisted of harvest body weight from 2 462 progenies （17 months old） from 28 families that were produced through artificial insemination using 39 parent fish. An animal model was applied to partition each weight value into a fixed effect, an additive genetic effect, and a residual effect. The average body weight of each family, which was measured at 110 days post-hatching, was considered as a covariate. For Bayesian analysis, heritability and breeding values were estimated using both the posterior mean and mode from the joint posterior conditional distribution. The results revealed that for additive genetic variance, the posterior mean estimate （σa^2 =9 320） was highest but with the smallest residual variance, REML estimates （σa^28 088） came second and the posterior mode estimate （σa^2=7 849） was lowest. The corresponding three heritability estimates followed the same trend as additive genetic variance and they were all high. The Pearson correlations between each pair of the three estimates of breeding values were all high, particularly that between the posterior mean and REML estimates （0.996 9）. These results reveal that the differences between Bayesian and REML methods in terms of estimation of heritability and breeding values were small. This study provides another feasible method of genetic parameter estimation in selective breeding programs of turbot.

Genetic parameters and response to selection for body weight in turbot(Scophthalmus maximus, Linnaeus)

Genetic parameters and response to selection were estimated for harvest body weight in turbot. The data consisted of 10 952 individuals of 508 full-sib families from three generations（G0, G1, and G2）. The heritability estimates for G0, G1, and G2 were 0.11±0.08, 0.18±0.09, and 0.17±0.07, respectively. Over three generations, the heritability estimate was 0.19±0.04. Maternal and common environmental effects were 0.10±0.04, 0.14±0.04, and0.13±0.03 within each generation and 0.12±0.01 across generations. The selection differential in growth was 18.24 g in G0 and 21.19 g in G1 corresponding to an average of 19.72 g per generation. The genetic gains were also calculated, they were 22.06 g in G1 and 11.93 g in G2, corresponding to 6.36% and 3.52% body weight. The total genetic gain after two generations was 10.10% body weight, which indicated that the selective breeding program for the body weight trait in turbot was successful.