Quantitative trait locus mapping of growth‐related traits in inter‐specific F1 hybrid grouper (Epinephelus fuscoguttatus × E. lanceolatus) in a tropical climate

Growth‐related traits are the main target of genetic breeding programmes in grouper aquaculture. We constructed genetic linkage maps for tiger grouper (Epinephelus fuscoguttatus) and giant grouper (E. lanceolatus) using 399 simple sequence repeat markers and performed a quantitative trait locus (QTL) analysis to identify the genomic regions responsible for growth‐related traits in F₁ hybrid grouper (E. fuscoguttatus × E. lanceolatus). The tiger grouper (female) linkage map contained 330 markers assigned to 24 linkage groups (LGs) and spanned 1,202.0 cM. The giant grouper (male) linkage map contained 231 markers distributed in 24 LGs and spanned 953.7 cM. Six QTLs affecting growth‐related traits with 5% genome‐wide significance were detected on different LGs. Four QTLs were identified for total length and body weight on Efu_LG8, 10, 13 and 19 on the tiger grouper map, which explained 6.6%–12.0% of the phenotypic variance. An epistatic QTL with a reciprocal association was observed between Efu_LG8 and 10. Two QTLs were identified for body weight on Ela_LG3 and 10 on the giant grouper map, which explained 6.9% of the phenotypic variance. Two‐way analysis of variance indicated that the QTL on Efu_LG13 interacts with the QTLs on Ela_LG3 and 10 with large effects on body weight. Furthermore, these six QTLs showed different features among the winter, summer and rainy seasons, suggesting that environmental factors and fish age affected these QTLs. These findings will be useful to understand the genetic structure of growth and conduct genetic breeding in grouper species.     

Conditioning,maturation and year‐round natural spawning of orange‐spotted grouper,Epinephelus coioides (Hamilton, 1822), in recirculating aquaculture system

The present experiment was aimed at studying the conditioning, maturation and natural spawning of orange‐spotted grouper, Epinephelus coioides, in a recirculatory aquaculture system (RAS). Thirty fish (n = 30; 3.35 ± 0.05 kg) were stocked in a circular tank of 125 m³ capacity fitted with an RAS for conditioning and broodstock development. After 15 days, 15 fish were implanted with 17 α methyl testosterone and letrozole at the rate of 5 mg and 0.2 mg/kg body weight, respectively, for conversion from female to male. The gonadal development started after 1 month, and by 90th day, 63.53 ± 3.78% and 2.07 ± 0.84% of the oocytes attained a size of 400–500 μm and 500–600 μm respectively. Natural spawning commenced in the RAS from 4th month onward after stocking and spawning continued round the year. The spawning pair showed courtship behaviour with a typical vertical burst of swimming just before release of gametes. The total number of eggs spawned during 1 year was 47.23 million with spawning frequency varying form 5 to 13 times per month. The association of spawning events with new moon day (lunar cycle) weakened as time progressed. The mean monthly fertilization and hatching rates varied from 77.80 ± 3.34% to 83.70 ± 1.76% and 82.80 ± 4.21% to 88.33 ± 1.39% respectively. The study proved that RAS is an efficient system that provides a stable, controllable and conducive environment for year‐round natural breeding of orange‐spotted grouper.     

Growth performance and disease resistance against Vibrio vulnificus infection of novel hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus)

Groupers are economically important for aquaculture in Thailand. A novel hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus) has been successful cross‐bred; therefore, the present work aimed to assess the hybrid's traits. The growth performance, strength and tolerance to a pathogenic bacterial infection of this hybrid were compared with its parent species, tiger grouper and giant grouper. The results of all measured growth parameters indicated that the hybrid strain grew fastest followed by giant and tiger grouper respectively. The expressions of the growth‐related genes, insulin‐like growth factor (IGF) I and II, were also analysed in fish muscle and liver which are the main target organs in fish growth regulation. Among tested species, similar expression patterns of IGF‐I and IGF‐II were detected in both organs. The levels of these genes in liver and muscle of hybrid and giant grouper were higher than those of tiger grouper comparable with the growth manner. After challenge with Vibrio vulnificus, the immunological parameters, clearance time of Vibrio in haemolymph and survival was measured to verify the fish immunity. Leucocyte number, lysozyme activity and the ability to eliminate the pathogen were very high in hybrid and giant grouper while these parameters were lower in tiger grouper. Correspondingly, the mortality rate of tiger grouper was higher than others and % survival at the end of observation time (15 days post challenge) was lowest in infected tiger grouper. Altogether, the results suggested that the hybrid grouper has desirable traits that will improve cultured grouper.     

发酵银杏叶对斜带石斑鱼生长性能、血浆生化指标与肝脏抗氧化指标的影响

本试验旨在研究发酵银杏叶对斜带石斑鱼生长性能、血浆生化指标与肝脏抗氧化指标的影响。配制添加不同水平[0(对照)、0.25%、0.50%]发酵银杏叶的饲料,投喂初始体重为12.6 g的斜带石斑鱼8周,每种饲料投喂3个网箱(重复),每个网箱投放30尾鱼。结果显示:1)生长性能指标各组间均没有显著差异(P>0.05)。2)与对照组相比,饲料中添加0.25%或0.50%发酵银杏叶均可显著降低血浆谷丙转氨酶(ALT)活性(P<0.05);饲料中添加0.50%发酵银杏叶还可显著降低血浆谷草转氨酶(AST)活性(P<0.05)。3)与对照组相比,饲料中添加0.25%或0.50%发酵银杏叶均可显著降低肝脏丙二醛(MDA)含量(P<0.05),显著提高肝脏超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH⁃Px)活性(P<0.05);饲料中添加0.50%发酵银杏叶还可显著提高肝脏过氧化氢酶(CAT)活性(P<0.05)。由此可见,饲料中添加0.25%或0.50%发酵银杏叶对斜带石斑鱼的生长性能无负面影响,还可提高斜带石斑鱼的肝脏抗氧化能力,且添加水平为0.50%时效果优于添加水平为0.25%时。     

A Pilot Safety Assessment for Recombinant Epinephelus lanceolatus Piscidin Yeast Powder as a Drug Food Additive after Subacute and Subchronic Administration to SD Rats

Recombinant Epinephelus lanceolatus piscidin (RELP) was previously shown to improve growth performance and immune response when used as a feed additive for Gallus gallus domesticus. However, the long-term toxicity of RELP has not be thoroughly investigated. In the present study, we evaluated the subacute and subchronic oral toxicities of RELP in SD rats by hematological, biochemical, and histopathological analyses. To determine subacute and subchronic toxicities, male and female rats were fed with RELP 1000 mg/kg bodyweight/day for 28 and 90 days, respectively. Bodyweight and food intake were unchanged by RELP treatment over the course of the studies. After exposure, samples of blood, heart, lung, liver, and kidney were collected and analyzed. Results demonstrated that RELP exposure did not cause any observable hematological, biochemical, or histological abnormalities in SD rats. Thus, RELP may be a safe feed additive for use in agriculture and aquaculture.     

青石斑鱼骨骼发育异常的形态特征

采用二重染色法对青石斑鱼Epinephelus awoara幼鱼的脊柱、尾鳍、背鳍和臀鳍骨骼发育异常进行观察.结果显示:脊柱发育异常包括脊柱前凸、脊柱后凸和脊柱侧凸以及椎骨的愈合、变形等症状;臀鳍畸形症状主要是近端支鳍骨的分叉;背鳍发育异常除了近端支鳍骨的末端发生分叉外,还有近端支鳍骨之间有软骨片存在;尾鳍骨发育异常主要表现为尾上骨数目不等,比正常鱼少一块或两块尾上骨.     

青石斑鱼与卵形鲳鲹卵黄囊仔鱼发育过程中脂肪特性及脂肪酸含量变化

定量研究了青石斑鱼(Epinephelus awoara)和卵形鲳鲹(Trachinotus ovatus)的卵黄囊仔鱼发育过程中脂肪特性及脂肪酸的变化。结果表明:两种仔鱼具有不同的脂肪组成,青石斑鱼卵黄囊仔鱼中性脂与极性脂比值为0.97～1.22;卵形鲳鲹卵黄囊仔鱼中性脂与极性脂比值为1.88～3.21。两种卵黄囊仔鱼的总脂含量均随发育而逐步下降,且都主要消耗中性脂。青石斑鱼卵黄囊仔鱼中性脂内含量高的脂肪酸为:18∶1n-9,16∶0,DHA,16∶1和18∶0;极性脂中含量高的脂肪酸为:DHA,16∶0,18∶0和18∶1n-9。卵形鲳鲹卵黄囊仔鱼中性脂中含量高的脂肪酸为:18∶1n-9,18∶2n-6,DHA,16∶4n-3和16∶0;极性脂中含量高的脂肪酸为:DHA,16∶0,18∶1n-9和18∶2n-6。青石斑鱼卵黄囊仔鱼发育至2日龄时中性脂主要脂肪酸均显著下降;而卵形鲳鲹卵黄囊仔鱼发育至1日龄时中性脂主要脂肪酸均显著下降。两种卵黄囊仔鱼极性脂中的主要脂肪酸均在1日龄时显著升高。上述结果表明尽管脂肪和脂肪酸组成存在显著差异,但青石斑鱼和卵形鲳鲹的卵黄囊仔鱼在发育过程中利用脂类的规律具有相似性。     

斜带石斑鱼MyD88基因的克隆与表达

本研究运用RACE-PCR技术获得斜带石斑鱼（Epinephelus coioides）髓样分化因子88（myeloid differentiation factor 88,MyD88）基因,并对该基因进行生物信息学和表达模式分析。研究结果表明1795bp的cDNA全长序列,包括ORF 870 bp、5＇UTR 243 bp和3＇UTR 682 bp,3＇UTR存在1个多聚腺苷酸加尾信号（AATAAA）和两个mRNA不稳定基序（ATTTA）。SMART软件预测该蛋白N端和C端分别存在死亡结构域和TIR结构域（Toll/IL-1 receptor homology domain,TIR）;与其它脊椎动物MyD88的序列同一性达57.1%～78.7%;用NJ法构建的系统进化树中,斜带石斑鱼MyD88和其它已报导的鱼类MyD88聚为一枝。qPCR检测结果显示MyD88基因mRNA主要表达于肝脏、脾脏、头肾和胸腺等组织。本研究为进一步探讨MyD88在斜带石斑鱼TLR信号传导中的作用奠定基础。     

不同动植物蛋白比配合饲料对点带石斑鱼生长的影响

在等蛋白的条件下,设计四种不同动植物蛋白比（3.8∶1,3.0∶1,2.2∶1, 1.4∶1）的饲料,制成软颗粒饲料投喂点带石斑鱼苗,经过64天的饲养对比试验,A、B、C、D各组鱼平均尾相对增重率为671%、664%、518%和443%,尾平均日增重为0.32g、0.32g、0.26g和0.21g,平均饲料系数分别为1.49、1.50、1.68、2.30;试验A、B、C组的丰满度与内脏比各组差异不显著（p〉0.05）,而D组的丰满度显著低于其它各试验组（p〈0.05）,内脏比显著高于其它各试验组（p〈0.05）。各试验组之间鱼的水分、粗蛋白、粗脂肪含量没有明显的差异（p〉0.05）,结果表明,当饲料中动植物蛋白比为3.0∶1时,鱼苗生长指标、鱼体品质较佳,当饲料中动植物蛋白比为2.2∶1时,饲料效率较高,饲料成本较低,鱼体品质较佳,这说明了点带石斑鱼饲料中适宜动植物蛋白比为3.0∶1～2.2∶1。