双列杂交法分析2个大菱鲆养殖群体的杂交效果

采用完全双列杂交法对2个大菱鲆(Scophthalmus maximus)养殖群体:西班牙群体(S)和英国群体(E)进行群体间杂交及群体内自繁,得到了S(♂)×S(♀)、E(♂)×E(♀)、S(♂)×E(♀)和E(♂)×S(♀)4个组合的子一代。对各交配组合的受精率、孵化率、畸形率、30日龄和70日龄稚鱼的体长、体质量等指标进行比较,结果表明,杂交组与自繁组在受精率、孵化率及畸形率等方面均不存在显著性差异;但杂交组30日龄稚鱼和70日龄稚鱼的体长、体质量与自繁组相比,表现出不同程度的杂种优势,其中S(♂)×E(♀)组30日龄稚鱼的体长杂种优势达到5.43%,E(♂)×S(♀)组70日龄稚鱼体质量杂种优势达到25.00%。实验初步显示,不同养殖群体间的杂交有可能是大菱鲆遗传改良的一条有效途径。     

Slaughtering method and dietary α-tocopheryl acetate supplementation affect rigor mortis and fillet shelf-life of turbot Scophthalmus maximus L.

The effects of dietary α‐tocopheryl acetate supplementation and different slaughtering methods were investigated on the flesh quality of farmed market‐size turbot Scophthalmus maximus (L). Turbot were divided into three groups and fed commercial diets, supplemented with different levels of α‐tocopheryl acetate at the following dietary inclusion levels: 72 (100), 547 (500), 969 (1000) (mg of α‐tocopheryl acetate kg^?1 diet, analytical values with diet codes in brackets). After 5 months, fish (mean weight 1056 ± 19.7 g) from each dietary treatment were sampled, applying three different slaughtering methods: (A) bleeding in ice water; (B) thermal shock, no bleeding; (C) percussion followed by bleeding in ice water. The time course of rigor mortis was evaluated, using pH, rigor index and mechanical compression tests. The results showed that the three parameters corresponded very well. Percussive stunning resulted in higher initial post‐mortem pH (P < 0.01) and a significantly delayed onset of rigor mortis (P < 0.05). Diet significantly affected shelf‐life, with fillets from fish fed diets 500 and 1000 having lower TBARS (thiobarbituric acid reactive substances) numbers from day 2 (P < 0.001) and less colour deterioration from day 7 of storage on ice onwards (P < 0.05). These results suggest that an increase in dietary α‐tocopheryl acetate before slaughter as well as careful selection of the slaughtering method may greatly enhance the flesh quality of market‐size turbot.     

Effect of increased water recirculation rate on algal supply and post-larval performance of scallop (Pecten maximus) reared in a partial open and continuous feeding system

In a commercial scallop hatchery spat production depends on a culture system which ensures high survival and good growth. Reuse of water with algae may increase the food exploitation and hence reduce the costs. Post-larvae of great scallop (Pecten maximus) were studied in a commercial hatchery using a partial open and continuous feeding tank system. Three different water recirculation rates (67, 83 and 92%) were tried out in two experiments with post-larvae originating from three spawning groups of ages between 43 and 57 days post-spawn, 316–886 μm shell-height and 1.1–9.6 μg ash-free dry weight. The post-larvae were held in sieves in tanks of 2500 l where a downwelling flow was maintained by airlifts. New water with a mix of monocultured algae was continuously added to the tanks at algal concentrations of 10 and 15 cells μl⁻¹ in experiment 1 (groups 1 and 2) and 2 (group 3), respectively. The algal supply to each sieve was reduced along with increased recirculation rate, but was kept between 6 and 13 cells μl⁻¹. Generally no significant differences in survival, growth or chemical content were found between the three recirculation rates, while few differences were found between and within groups. Large variation in survival was found between and within groups (1–81%). Highest survival was found in experiment 1, and where post-larvae from two settlements were used, the first settlement survived better than the second. The daily growth ranged from 15 to 62 μm shell-height and from 0.3 to 2.6 μg ash-free dry weight. The scallop post-larvae could well be reared at all three recirculation rates studied as an increase from 67 to 92% did not seem to affect the post-larval performance seriously. The algal supply, however, had to be compensated by an increasing number of cells (>10 cells μl⁻¹) when increasing the recirculation rate.     

大菱鲆hepcidin抗菌肽基因的克隆及在大肠杆菌中的高效表达

通过同源克隆结合RACE的方法从大菱鲆(Scophthal mus maximus)肝脏中克隆了大菱鲆hepcidin抗菌肽基因全长cDNA(GenBank accession number AY994074)。大菱鲆hepcidin基因cDNA全长778bp,包含有1个273bp的开放阅读框,编码1个长90氨基酸的前体肽。将大菱鲆hepcidin抗菌肽基因的成熟肽序列重组至原核表达载体pGEX-4T-1中,用IPTG诱导后,SDS-PAGE电泳显示在29ku处有特异性蛋白条带出现,表达的融合蛋白主要以包涵体形式存在,融合蛋白约占总蛋白的26%。Western-blotting分析发现表达的融合蛋白可以特异性地与GST抗体相识别。这些结果表明大菱鲆hepcidin抗菌肽基因成功实现了原核表达。     

Effects of hypoxia on respiratory physiology of turbot, Scophthalmus maximus

Variations in respiratory and acid-base status were studied in turbot (Scophthalmus maximus) during progressive severe hypoxia followed by recovery under normoxic conditions. The first behavioural strategy of turbot under hypoxia was an increase in amplitude and frequency of ventilation. Consequently, standard O₂ consumption remained unchanged over a broad range of O₂ tensions, until a low critical level of 30 mmHg. The hyperventilation induced a moderate blood alkalosis, compensated by a lactic acidosis. The fact that blood pH did not decrease below control values could be explained by the retention in white muscle of most of the lactate produced and by a high capacity for H⁺ excretion. During the recovery period, the marked increase in O₂ uptake corresponding to an oxygen debt repayment, was partly related to the lactate elimination. When total energy contributions of aerobic and anaerobic processes were assessed in terms of ATP, the anaerobic contribution, estimated at the deepest hypoxia level, was higher than 20% of the total energy budget and appeared to totally compensate for the decline in aerobic metabolism. Moreover, the high value of O₂ tension in arterial blood in normoxia and during recovery from hypoxia showed high diffusing capacity of gills in turbot. Our results explain the high tolerance of turbot for O₂ deficient waters.     

Partial decontamination of rotifers with ultraviolet radiation: the effect of changes in the bacterial load and flora of rotifers on mortalities in start-feeding larval turbot

Exposure of the rotifer Brachionus plicatilis to ultraviolet radiation in 1 mm deep liquid layers at an energy intensity of 38 mW cm⁻² reduced the rotifer bacterial load by >90% within 2 min. Such radiation doses had no significant effect upon rotifer viability, fatty acid composition, swimming or feeding activity. The surviving bacterial flora of irradiated rotifers was similar to that of un-irradiated rotifers and there was no evidence of major differences in sensitivity to ultraviolet radiation between different bacteria. For irradiation of large numbers of rotifers, a flow-through cell was used, operated with rotifer densities of 200 ml⁻¹ and a flow rate of 1.5 l min⁻¹. In two separate field trials involving groups of 34,000 turbot larvae per group, higher survival was found in groups receiving ultraviolet-irradiated rotifers in which the bacterial load was reduced by 88%. This was attributed to the slower rate of colonisation of the larval gut by bacteria, as a consequence of the lower bacterial load on the rotifers. Attempts to introduce specified bacteria into the larval turbot gut in significant numbers by colonisation of either normal or irradiated rotifers with particular bacteria were unsuccessful.     

Water quality and nitrogen budget in turbot Scophthalmus maximus culture system supplemented with lactic acid bacteria

To understand the nutrient utilization efficiency and distribution in indoor fish culture system under treatment of probiotics, this study examined water quality and nitrogen budget in turbot Scophthalmus maximus culture system supplemented with four strains of lactic acid bacteria (LAB) isolated from fishery products. The results showed that the concentration of ammonia nitrogen (NH?‐N) and nitrite nitrogen (NO?‐N) in LAB treatments were all significantly lower (p < 0.05) than in the control group. The nitrate nitrogen (NO?‐N) in LAB treatments showed no significant differences (p > 0.05) compared with control group. The fish feed and water exchange accounted for 79.07% and 17.02% of total N input respectively. For N output, the drainage and residual diets in LAB treatment accounted for 24.50%–25.80% and 1.33%–1.60% respectively, and they were significantly lower than in the control group (27.60% and 2.20% respectively). Fish growth and lost N in LAB treatments accounted for 27.10%–30.50% and 11.00%–18.50% respectively, and they were both significantly higher (p < 0.05) than in the control group (22.30% and 5.30% respectively). The results indicated that the indigenous LAB strains were capable of improving fish growth, and reducing NH?‐N and NO?‐N level (at concentration of 10⁵ cfu/ml) by directly adding in S. maximus culture water. Moreover, specific strains of LAB may increase nitrogen loss by promoting denitrification process in culture system.     

二氟沙星在大菱鲆(Scophthalmus maximus)体内的药代动力学特征

为给大菱鲆临床安全用药提供依据,对二氟沙星在健康大菱鲆体内的药代动力学特征进行了研究。在水温为14–17℃条件下,以20 mg/kg体重剂量静脉注射和口服二氟沙星,分别于给药后的15、30 min和1、2、4、6、8、12、16、24、36、48、72、96 h采血及各组织,利用高效液相色谱测定各组织和血浆中的二氟沙星含量,采用DAS 2.0自动药动学软件分析药代动力学参数。结果显示,静注给药后,血浆中二氟沙星的药-时曲线符合零级吸收二室开放模型,消除半衰期(t1/2β)和药时曲线下面积(AUC0-t)分别为30.02 h和440.37 h·μg/ml;口服给药后,血浆中二氟沙星的药-时曲线符合一级吸收二室开放模型,4 h时血药浓度达到最大值(Cmax)6.32μg/ml,t1/2β和AUC0-t分别为94.72 h和246.66 h·μg/ml,生物利用度(F)为56.01%,肾脏和肌肉内的药物浓度较高,而肝脏内相对较低。拟合的最佳口服给药方案为:按鱼体重每次给药11.94 mg/kg,每日1次。     

Influence of 5′‐inosine monophosphate and 5′‐guanosine monophosphate on growth,feed digestibility and activity of digestive enzymes in turbot Scophthalmus maximus

We evaluated the influence of different proportions of 5′‐inosine monophosphate (IMP) and 5′‐guanosine monophosphate (GMP) on growth, feed digestibility and activity of digestive enzymes of turbot Scophthalmus maximus. Weight gain and daily feed intake were significantly higher in S. maximus fed with IMP or GMP, in comparison with fish fed with neither IMP nor GMP. The growth of 0.05% IMP + 0.05% GMP group was the best, and the intestinal digestive function was improved. The addition of IMP and GMP to fish diets significantly increased the apparent feed digestibility coefficient of dry matter and protein, as well as intestinal protease activity. The highest intestinal protease activity was observed in fish fed with 1 g/kg IMP. However, the lipase activity in hepatopancreas decreased significantly after addition of nucleic acid. According to our results, the optimal level of dietary IMP is 1 g/kg, which is in line with most of the growth performance and feed digestibility.     

The plasticity of vision and body development of turbot Scophthalmus maximus larvae Under different light spectra

This study was aimed to find out the effect of five light spectra (white, LDW; blue, LDB; green, LDG; red, LDR and yellow, LDY) on the visual development and growth performance of turbot (Scophthalmus maximus) larvae. The number (per 100 μm) of cone cells, outer nuclear cells, ganglion cells, the ratio of outer nuclear to cone and ganglion cells, lens diameter and the minimum separable angle were determined. Variations in growth performance in total length, body mass and body colour were also examined. The results showed that the LDB group underwent metamorphosis faster than did the other groups and attained the greatest total length, body mass and light sensitivity. The LDB group also completed the body colour variation prior to the other groups. The LDG group exhibited a high mortality rate since 25 dph (days post‐hatching). We arrived at the conclusions that the spectra could affect the vision and body development of turbot larvae specifically and the blue light had the enhancing efficiency during this process, followed by the white and yellow light. The red light imposed an inhibiting effect on these variations. Our study highlighted the significance of light condition and provided the reference for the farming.