大菱鲆胚胎玻璃化方法研究

用大菱鲆(Scophthalmus maximus)神经期胚对6种抗冻剂的毒性进行检测,发现其毒性排列为1,2-丙二醇(PG)<甲醇(MeOH)<甘油(Gly)<二甲基甲酰胺(DMF)<乙二醇(EG)<二甲亚砜(DMSO).以DMF为主因子配制和筛选出11种玻璃化程度较好的玻璃化液,并用大菱鲆肌节期胚对其中5种玻璃化程度最好的玻璃化液进行检测,结果显示,A4(DMSO 20%+DMF 25%)、A7(DMSO 25%+DMF 20%)较适合于大菱鲆胚胎的平衡处理,利用A4和A7平衡处理神经期胚、肌节期胚、心跳期胚、出膜前期胚,结果显示大菱鲆神经胚和肌节胚对玻璃化液的适应能力较强.实验测试出不同时期胚胎在两种玻璃化液中的成活率,为大菱鲆各期胚胎在玻璃化液中的平衡处理提供了依据.利用大菱鲆肌节胚对不同的平衡步骤进行了筛选,发现五步法的平衡效果较好.     

Stress responses of larval turbot, Scophthalmus maximus L., exposed to sub-lethal concentrations of petroleum hydrocarbons

Turbot larvae were exposed to dilutions of the water soluble fraction (WSF) of crude oil (1–25%), in a laboratory flow-through system. Whole body immunoreactive cortisol (IRC) content of premetamorphic 345 degree C day and early metamorphosing 450 degree C day larvae (23 and 30 days post hatch, respectively) was elevated when exposed to 25% WSF for 6 h, but the lower WSF concentrations did not induce IRC elevations. Larvae of 450 degree C days exposed to WSF for 6 h and then left in clean sea water for 24 h showed recovery of IRC, whilst the IRC content of 450 degree C day larvae exposed to WSF for 30 h remained elevated. Whole body thyroxine content of 345 degree C day larvae exposed to 25% WSF for 6 h was significantly elevated, which may have implications for larval development/metamorphosis. However, whole body triiodothyronine content of these larvae was not altered by WSF-exposure. Furthermore, larvae of 450 degree C days, WSF-exposed for 6 h or 30 h showed no thyroidal disturbance. Larvae of 345 degree C days exhibited significantly elevated whole body adrenaline and noradrenaline content after exposure for 6 h to 25% WSF; however, more diluted WSF did not influence adrenaline or noradrenaline content. These studies have demonstrated that larvae of 345 and 450 degree C days can successfully mount endocrine stress responses but that environmentally realistic concentrations of petroleum hydrocarbons do not induce these responses.     

Genetic analysis of production traits in turbot (Scophthalmus maximus) using random regression models based on molecular relatedness

Reliable estimates of genetic parameters for growth traits as a trajectory of age are needed to optimize existing turbot breeding programmes. To evaluate the potential of early selection strategies, the use of biometric body measurements, length (L), width (W) and area (A), at early ages as alternative indicators for the selection trait at harvest was explored. Random regression model (RRM) based on molecular relatedness (MR) was used to analyse the trajectory of genetic parameters for growth traits in turbot from 162 to 756 days posthatch (dph). Heritability estimates for body weight (BW) ranged from 0.34 to 0.54. Heritability estimates for W, A and L were also moderate to high ranging from 0.18 to 0.43. Estimates for L and W declined with age, while those for A increased towards harvest age. Genetic (r_G) and phenotypic (r_P) correlations between BW and the three morphometric traits L, A and W were estimated using simple bivariate animal models at young (AC1), medium (AC2) and old (AC3) age classes. Correlations between BW and morphometric body traits were high, ranging from 0.7 to 0.9 in all three age groups. Genetic correlations between traits were highest (>0.9) in AC3. To explore the potential for early selection, genetic correlations were derived from the RRM between all days of measurement for all traits separately. From dph 300 onwards, intratrait estimates of r_G were moderate to high (above 0.7 for dph 410 and higher ages for traits BW, L and A). Results showed that genetic selection for BW, L and A is promising and that A and L could be successfully used as alternative indicator traits if measurements of BW are not available. Large BW and A at harvest could be achieved as a correlated response to early selection for these traits at around 500 dph.     

Juvenile turbot (Scophthalmus maximus L., 1758) farmed in a modern low-water exchange RAS device: Growth performance using different diets and its commercial implications

One step to improve the economics of Recirculated Aquaculture Systems (RAS) is the use of the right feed. A 12-week lasting growth trial with juvenile turbot (Scophthalmus maximus) with an average initial weight of 54.4 ± 19.3 g evaluated the economic impact of choosing the best feed. Therefore, commercially available feeds recommended for turbot culture, two floating (feed 1 and feed 3) and one sinking (feed 2), were tested in a low-water exchange RAS device. Compositions of the macronutrients for the floating diets were 56.0% (protein), 12.0% (fat), 1.1% (fiber), and 10.0% (ash) for feed 1, which will be referred to as Floating 1, and 55.0% (protein), 16.0% (fat), 0.7% (fiber), and 11.0% (ash) for feed 3, which will be referred as Floating 2. The macronutrient composition of feed 2, which will be referred to as Sinking, was 50.0% (protein), 15.0% (fat), 1.4% (fiber), and 9.9% (ash). Growth performance differed significantly between feeds; the specific growth rates (SGR) ranged between 0.92% d^?1 (Sinking) and 1.25% d^?1 (Floating 1 and 2), resulting in a significantly higher growth rate for the floating feeds. Feed conversion ratios (FCR) were also significantly different, and Sinking showed the highest FCRs during the experiment. We assume that this was caused by the different swimming characteristics of the feeds and the foraging behavior of the fish instead of the different nutritional compositions of the diets. Including retailer prices, the feed costs per kg produced fish differed between 9.3% and 20.2%, resulting in the highest production costs for the Sinking. Therefore, finding the right feed for turbot and optimizing the feeding regime according to its requirements will improve the economic feasibility of turbot culture.     

不同放养量与水交换率对大菱鲆幼鱼的养殖效果及水质条件的影响

经过 6 0d的试验养殖 ,在每日 2、 4、6个循环水量的条件下 ,研究放养量从 0 .74～ 1.99kg/m2 大菱鲆 (Scophthalmusmaximus)幼鱼的平均体重增长、养殖成活率、饵料系数和养殖水中的溶解氧、氨氮含量等养殖生态状况。结果表明 ,日水循环量为 2个全量时 ,放养量为 1.5 4kg/m2 的实验组的平均体重增重与放养量低的实验组 (0 .75kg/m2 、1.0 1kg/m2 、1.31kg/m2 )平均体重增重无显著差异 (P >0 .0 5 ) ,而与高于此实验组 (1.74kg/m2 、1.99kg/m2 )的增重比较则差异显著 (P <0 0 5 ) ;水循环量的增加可以改善水质条件 ,加快幼鱼的生长速度 ,但对幼鱼的饵料系数影响不大。     

Lipid digestion in turbot (Scopthalmus maximus) 11: Lipolysis in vitro of 14C-labelled triacylglycerol,cholesterol ester and phosphatidylcholine by digesta from different segments of the digestive tract

Preparations of digesta from the stomach, foregut, hindgut and rectum of turbot (Scophthalmus maximus) were assayed for the ability to hydrolyse glycerol tri[1-¹⁴C]oleate (¹⁴C-TAG), 1,2-di[1-¹⁴C]palmitoyl L-3-phosphatidylcholine (¹⁴C-PC) and cholesterol [1-¹⁴]oleate (¹⁴C-CE) over 1,2,3 and 17h. In the assay of foregut digesta with ¹⁴C-TAG substrate, 37.8% of the total radioactivity was found in the FFA class after the first hour of incubation. This value increased to a maximum of 68.5% of the available label after 17h incubation. Over the same time the proportion of radioactivity in diacylglycerols (DAG, 31.6%–7.4%) decreased while that in the monoacylglycerols increased (MAG, 14.0%–22.3%). In assays of digesta from the hindgut and rectum, after 1 h of incubation, the proportion of radioactivity recovered in FFA represented 64.9% and 74.8%, respectively, whereas the proportions in both DAG and MAG decreased with incubation time. Similarly to ¹⁴C-TAG, the highest rate of lipolytic hydrolysis of ¹⁴C-CE occurred in digesta from the posterior digestive tract where the proportions of radioactivity recovered in FFA of the hindgut (50.0%) and rectum (81.9%) preparations were substantially higher than those of the stomach (3.5%) and the foregut (14.4%) after 1h. With ¹⁴C-PC as substrate the levels of radiolabelled FFA in both the foregut and the hindgut (2.4% and 7.6%, respectively) were markedly lower than the 37.5% in the rectum. The results suggest that the posterior digestive tract is very active in non-specific and phospholipid lipolysis and a region where the major part of lipid digestion takes place.     

Characterization of nodavirus and viral encephalopathy and retinopathy in farmed turbot, Scophthalmus maximus (L.)

An outbreak of nodavirus infection in turbot larvae is described with respect to histopathology, immunohistochemistry, cell culture cultivation, RT-PCR amplification and sequence analysis of the capsid protein gene RNA2. Affected turbot developed classical signs of viral encephalopathy and retinopathy (VER) with abnormal swimming behaviour and high mortality levels. In the acute stage of infection, light microscopy revealed vacuolation of the central nervous system (CNS), with positive immunohistochemical staining for nodavirus. Later in the infection, CNS lesions appeared more chronic and contained clusters of cells immunopositive for nodavirus. Bacterial overgrowth in the intestines of the fish may have provoked or influenced the course of the nodavirus infection. We were unable to propagate the virus in cell culture. While RT-PCR using primers designed to detect Atlantic halibut nodavirus gave negative results, further testing with primers complementary to a more conserved region of RNA2 resulted in amplification of a product of the expected size. The entire RNA2 segment was cloned and sequenced. Sequence alignment showed that the turbot nodavirus (TNV) was different from previously described fish nodaviruses. In addition, phylogenetic analysis based on an 823 nt region of the sequence indicated that TNV clustered outside the four established fish nodavirus genotypes, suggesting a fifth genotype within the betanodaviruses.     

Cryopreservation of turbot Scophthalmus maximus (L.) sperm: fertilization and hatching rates

The present paper assesses the fertilization and hatching rates of an artificial fertilization series (n=1153) using fresh and cryopreserved sperm from 49 specimens of turbot Scophthalmus maximus (L.), carried out to confirm the results of a previous study, with the ultimate aim of transferring these cryo‐preservation techniques to commercial hatcheries. No significant differences were found between the fertilization rates of the two groups (fresh and cryopreserved sperm) when their respective fertility rates were >69.2%, which was the case in 75% of all fertilizations. Likewise, no significant differences in hatching rates were found. In order to use the cryopreserved sperm more efficiently, a key concern for commercial use of this technique, we also experimented with a lower sperm:diluent ratio (1:1) than used previously at our centre. We also compared the traditional 0.5‐mL straws with 2‐mL cryotubes able to contain a higher volume of sperm, finding no significant differences in the resulting fertilization and hatching rates. In conclusion, the use of cryopreservation for turbot sperm presents major advantages for broodstock management in commercial hatcheries.     

Dietary krill hydrolysates affect the expression of growth‐related genes in juvenile turbot (Scophthalmus maximus L.)

A 10‐week feeding experiment in indoor flow‐through seawater system was conducted to investigate the effects of dietary krill hydrolysate on the expression of growth‐related genes in juvenile turbot (Scophthalmus maximus L.; initial body weight 9.45 ± 0.01 g). Three isonitrogenous and isolipidic experimental diets containing high plant protein were formulated to contain 0 (control), 50 g/kg (LKH) and 100 g/kg (HKH) krill protein hydrolysate (KH) to replace fishmeal, respectively. Triplicate groups of 30 fish were fed for 10 weeks to apparent satiation twice daily. At the end of the feeding trial, the mRNA expressions of insulin‐like growth factor (IGF‐1) gene in liver, peptide transporters (PepT1) gene in pyloric caeca and proximal intestine and neuropeptide Y (NPY) gene in brain in all groups were determined. IGF‐1, PepT1 and NPY expression levels in HKH group were significantly increased compared with those of LKH and control (p < 0.05), which was consistent with the SGR, feed efficiency, PER and PPV. These results indicated that dietary 100 g/kg krill hydrolysate could improve growth performance and upregulate the mRNA expression of IGF‐1, PepT1 and NPY genes in juvenile turbot.     

Assessing feasibility of replacement of fishmeal with enzyme‐treated feather meal in the diet of juvenile turbot (Scophthalmus maximus L.)

A feeding trial was conducted to examine the potential of enzyme‐treated feather meal (EFM) as a fishmeal substitute in the diet of turbot. Fishmeal (650 g/kg) was incrementally replaced (0, 160, 320, 480, 640 and 800 g/kg) by EFM (0, 80, 160, 240, 320, 400 g/kg) to prepare six experimental diets (Control, EFM8, EFM16, EFM24, EFM32 and EFM40). Diet EFM24 was supplemented with lysine and methionine to form seventh diet (EFM24 + AA). The eighth diet was formulated with 240 g/kg steam‐processed feather meal to replace 480 g/kg fishmeal (SFM24). Eight diets were each fed to triplicate groups of juvenile turbot (37.47 g) in a recirculating aquaculture system for 7 weeks. The results showed that fish fed diet EFM24 grew better than those fed SFM24 (p < .05). The growth performance, body composition and serum biochemical indices of fish fed diet EFM8 were not statistically different compared to the control treatment (p > .05). However, further increase in fishmeal replacement (32%–80%) affected negatively growth, nutrients digestibility, serum biochemical indices and body composition (p < .05). Supplementation of lysine and methionine (EFM24 + AA) significantly improved growth performance and diet utilization compared to EFM24 (p < .05). Altogether results suggested that the EFM could comprise 80 g/kg in a diet for juvenile turbot by concurrent reduction of the fishmeal content by 160 g/kg without lysine and methionine supplementation.