Construction and expression of DNA vaccine against reddish body iridovirus and evaluation of immune efficacy in turbot (Scophthalmus maximus)

Turbot aquaculture is a very important industry in China. However, it is hampered because of viral reddish body syndrome (VRBS) and high mortality caused by piscine turbot reddish body iridovirus (TRBIV). TRBIV virus is an icosahedron‐like and cytoplasmic DNA virus, belonging to Iridoviridae, Megalocytivirus. In previous studies, we have identified two antigen mimotopes using bioinformatics and constructed prokaryotic expression vectors. In this study, a fragment of major capsid protein (MCP) gene with the two antigenic epitopes was cloned into eukaryotic expression vector pVAX1, to generate a recombinant plasmid pVAX1‐TRBIV‐MCP. The plasmid DNA was transferred into turbot cell line TK using liposome, and transient expression was detected using RT‐PCR. After injection into turbot (Scophthalmus maximus), the expression of the antigen gene was analysed using RT‐PCR and was shown to express in all tested tissues in vaccinated fish 2 and 7 days post‐vaccination. The cumulative mortalities in the vaccinated and unvaccinated control fish were 30% and 88% respectively. Immune responses and upregulation of the expression of chemokine receptor, tumour necrosis factor, interferon and interferon‐induced antiviral molecules were observed in the vaccinated fish 60 h post‐vaccination. These results demonstrate that the vaccinated turbots had higher survival rate and produced specific serum antibodies following the TRBIV challenge. More studies are needed to develop and apply the promising DNA vaccine for virus control in turbot.     

菜籽油替代鱼油对大菱鲆幼鱼生长、脂肪酸组成及脂肪沉积的影响

本试验旨在研究饲料中菜籽油替代鱼油对大菱鲆(Scophthalmus maximus L.)幼鱼生长、脂肪酸组成以及脂肪沉积的影响。以菜籽油分别替代0、33.3%、66.7%和100.0%的鱼油,配制4种等氮等脂实用饲料。选择初始体重为(5.89±0.02)g的大菱鲆幼鱼420尾,随机分为4组,每组3个重复,每个重复35尾。每种饲料随机投喂1组试验鱼,养殖周期为92 d。结果表明:1)随菜籽油替代水平的升高,大菱鲆幼鱼的终末体重和特定生长率均有下降的趋势,而肝体比则有升高的趋势,其中全菜籽油组的终末体重和特定生长率显著低于全鱼油组(P0.05),肝体比则显著高于全鱼油组(P0.05)。菜籽油替代水平并未显著影响大菱鲆幼鱼的存活率、饲料效率、摄食率和表观净蛋白质利用率(P0.05)。2)菜籽油替代水平并未显著影响大菱鲆幼鱼的体成分、肌肉脂肪含量以及饲料脂肪表观消化率(P0.05),但显著影响了大菱鲆幼鱼的肝脏脂肪含量(P0.05)。66.7%菜籽油组和全菜籽油组肝脏脂肪含量显著高于全鱼油组(P0.05)。3)肝脏和肌肉脂肪酸组成与饲料脂肪酸组成呈正相关关系;相对于全鱼油组,66.7%菜籽油组和全菜籽油组肌肉和肝脏中C18∶2n-6(亚油酸)和α-C18∶3n-3(α-亚麻酸)含量显著升高(P0.05),而C20∶5n-3(EPA)和C22∶6n-3(DHA)含量显著下降(P0.05)。综上可知,从营养品质角度考虑,在大菱鲆幼鱼饲料中菜籽油替代鱼油水平应低于66.7%     

Transition from endogenous to exogenous nutritional sources in larval Black Sea turbot Psetta maxima

ABSTRACT: Early growth, yolk and oil globule absorption, early morphological development and initial feeding were studied in the Black Sea turbot Psetta maxima . Based on energy transition and morphological development, the nutritional transition process from endogenous to exogenous sources was divided into six phases: (i) primordial phase (from hatching to ≈ 30 h after hatching, HAH); (ii) organogenesis phase (to ≈ 90 HAH); (iii) onset of feeding (to ≈ 110 HAH); (iv) early feeding (to ≈ 190 HAH); (v) intensified feeding (to ≈ 230 HAH); and (vi) completion of oil globule absorption (to beyond 345 HAH). Based on comparisons with early life stage features of other marine species, the turbot larvae were shown to possess the following characteristics: (i) oil globule remaining for a long period, resulting in an extended mixed feeding period; and (ii) feeding rate extremely high in larvae immediately following final absorption of the oil globule. These features in early turbot larvae were regarded as advantageous for survival in a rearing condition, although the coincidence of initial feeding with completion of yolk absorption signaled a period of leveled-off growth rate.     

饲料脂肪源对大菱鲆幼鱼生长性能和肌肉脂肪酸组成的影响

以不同脂肪源配制成等氮等脂的7种试验饲料,对体重为(27.31±0.10)g的大菱鲆幼鱼进行40 d的饲养试验,旨在探讨饲料脂肪源对大菱鲆幼鱼生长性能和肌肉脂肪酸组成的影响。7种试验饲料的脂肪源分别为鱼油、豆油、菜籽油、花生油、猪油、鱼油+豆油(鱼油∶豆油=1∶1)和鱼油+豆油+猪油(鱼油∶豆油∶猪油=3∶4∶3)。每种饲料设3个重复,每个重复12尾鱼。结果表明:鱼油+豆油组的增重率和特定生长率显著高于鱼油组、豆油组和菜籽油组(P0.05),花生油组、猪油组和鱼油+豆油+猪油组的增重率和特定生长率则显著低于其他各组(P0.05)。饲料系数以鱼油+豆油组最低,猪油组最高。各组干物质和总磷表观消化率差异不显著(P0.05),猪油组和鱼油+豆油+猪油组的粗脂肪表观消化率显著低于其他各组(P0.05)。花生油组、鱼油+豆油组和豆油组的粗蛋白质表观消化率显著高于猪油组(P0.05)。摄食不同脂肪源饲料的大菱鲆幼鱼鱼体水分、粗脂肪和粗灰分含量差异不显著(P0.05)。猪油组鱼体粗蛋白质含量显著低于菜籽油组、花生油组和鱼油组(P0.05),其余各组间无显著差异(P0.05)。除C14∶0以外,各组大菱鲆肌肉中的脂肪酸含量和相应饲料中脂肪酸含量呈正相关。大菱鲆幼鱼肌肉中n-3多不饱和脂肪酸(PUFA)含量以鱼油组和鱼油+豆油组较高,而以花生油组和猪油组较低。结果提示:豆油和菜籽油是大菱鲆幼鱼饲料良好的脂肪源,鱼油和豆油按1∶1混合添加则能使大菱鲆幼鱼更好地生长。     

循环水养殖大菱鲆试验

通过循环水养殖大菱鲆,养殖250 d后大菱鲆平均体重550 g,平均日增重2.3 g,饵料系数1.1。循环水养殖大菱鲆,既能减少环境污染,又能节水、节煤、节电,1000 m2养殖面积能降低生产成本近10万元。     

有水与无水保活运输对大菱鲆生理应激及鱼肉品质的影响

为探究大菱鲆分别在有水及无水条件下运输过程中生理生化指标及肌肉品质的变化,为大菱鲆的保活运输提供参考.将大菱鲆进行暂养、降温、充氧包装后进行模拟运输,并在运输不同时间段取样,检测大菱鲆生理生化指标及肌肉指标.结果显示,模拟运输18 h后,有水运输组和无水运输组中的大菱鲆存活率仍为100％.大菱鲆肌肉中水分含量、粗脂肪、...     

The immune response of turbot, Scophthalmus maximus (L.), skin to high water temperature

The immune responses of mucus from the skin of turbot, Scophthalmus maximus, were studied in relation to changing water temperature. Groups of fish were exposed to a programmed increase of 3 °C per 48 h, until the experimental water temperatures of 16, 20, 23, 25, 27 or 28 °C were reached. After 48 h at the relevant temperature, the expressions of immune‐related factors were determined, including immunoglobulin M (IgM), IL‐1β, hepcidin, transferrin, lysozyme, acid/alkaline phosphatase and superoxide dismutase using RT–PCR and spectrophotometric methods. Significant changes in mucus immunity were observed, which paralleled with those previously reported for serum in other fish species. Hence, it is suggested that the serum and mucus immune system of turbot have a similar regulatory system. This information could be useful in better understanding the role of the mucus as a component of the innate immune system.     

Survival Rates of Black Sea Turbot (Psetta maxima maeotica, L. 1758) Broodstock Captured by Gill Nets from Different Depths and their Adaptation Culture Conditions

A study was performed during Spring 2002 to determine the survival rates of Black Sea Turbot (Psetta maxima maeotica) broodstock captured by gill nets from different depths (20 m, 20–45 m, and 45 m) in Sinop Bay (Black Sea, Turkey) and their adaptation to culture conditions. The weight of captured females ranged between 1.6 and 5.5 kg, while males ranged between 1.1 and 3.7 kg. Within 23 h of capture the fish were transported to Çanakkale (Marmara Sea, Turkey). During transportation, the stocking density ranged from 19 to 40 kg/m³ and no mortality was recorded. At the end of the fishing operations, the survival rates were calculated for Group 1 (20 m), Group 2 (20–45 m), and Group 3 (45 m) as 24.9, 71.4, and 92%, respectively. There were significant differences (p < 0.05) between the survival rates of the groups. Eggs and sperms were obtained by hand-stripping. The mean fertilisation rate of the eggs was 3.19%. This low fertilisation rate was due to overripened eggs. At the end of adaptation period of 1 month, the survival rates of the broodstock were found to be 14.2, 45.4, and 48.3% for Groups 1, 2, and 3, respectively. No significant difference was found between the survival rates of the broodfish during the adaptation period (p > 0.05).     

Substituting fish meal with poultry by-product meal in diets for black Sea turbot Psetta maeotica

A 60 days feeding experiment was carried out with Black Sea turbot Psetta maeotica to determine the amount of poultry by‐product meal (PBM) that could replace fish meal (FM) in formulated diets without reducing growth performance. Juvenile Black Sea turbot (initial average weight, 30 g) were fed five isoenergetic (gross energy, 20.5 ± 0.21 kJ g^?1 diet) and isonitrogenous diets (protein content, 550 ± 0.35 g kg^?1). The control diet used white FM as the sole protein source, the other four diets were prepared to replace FM protein at levels of 25%, 50%, 75% and 100% with PBM. The fish readily accepted all experimental diets and no mortality were recorded during the trial. There were no significant differences in growth performance of turbot (P < 0.05) fed the diets with 25% and 50% replacement levels compared with fish offered the control diet (100% FM), however, final body weight and specific growth rate values in the 50% replacement diet were about 8% lower than those of the control. Total nitrogen excretion in fish fed 50% replacement diet were about 10% higher than the control group, even though these parameters were not found to be statistically different. At the levels of 750 and 1000 g kg^?1 of the protein, PBM inclusion caused a severe decrease in growth performance, feed utilization, protein efficiency ratio and per cent nitrogen retention. The results in the present study indicate that up to 25% of FM protein can be replaced by PBM protein without causing reduction in growth performance, nutrient utilization and nitrogen retention.