Isolation and characterization of microsatellite loci in Hexagrammos otakii based on 2b-RAD method

In this study, we isolated 20 novel microsatellites loci associated with the growth of Hexagrammos otakii (Fat greenling) by using 2b-RAD sequencing method. The characteristics of 20 microsatellite loci were amplified in 105 H. otakii individuals which came from four different groups and tested by Capillary electrophoresis. The number of allele of the 20 microsatellite loci ranged from 8 to 26 with an average of 19.95. PIC value ranged from 0.1659 to 0.9227 with an average of 0.7555. Observed and expected heterozygosity varied from 0.0667 to 0.8571 and from 0.1710 to 0.9314, respectively. Highly polymorphic characteristics were observed in each microsatellite loci of the study except HO6. Further research showed that 10 microsatellite loci had transferability in Hexagrammos agrammus. In this study, high polymorphism and genetic diversity using the 15 polymorphic microsatellite loci suggest that they are suitable for investigating the fine-scale population structure, genetic relationship and further evaluating the artificial reproduction strategy of H. otakii.     

基于16S rRNA高通量测序分析大泷六线鱼表皮粘液及肠道内容物微生物多样性

大泷六线鱼(Hexagrammos otakii)是一种具有代表性的高价值冷水性鱼类。通过分析大泷六线鱼表皮粘液及肠道内容物微生物菌群特征,了解其微生物多样性及所携带的自身特有的潜在病原微生物情况。采集设施化车间养殖的大泷六线鱼,提取表皮粘液和肠道内容物基因组DNA,通过16S rRNA高通量测序技术和生物学分析方法,对不同样本的V3+V4区基因文库进行分析。结果表明,大泷六线鱼表皮粘液和肠道内容物样本拥有共同的OTUs为33个,且Venn图呈现了不同来源样本之间的相似性和差异性。Rank-abundance曲线显示了不同样本的均匀度和丰富度,测序数据合理、可信。Alpha指数平均值显示肠道内容物微生物丰富度较高,而表皮粘液微生物多样性较高;Beta多样性显示了不同来源样本间的异质性及同一来源样本间的相似性。从门水平上看,优势菌门均为蓝菌门（Cyanobacteria）、变形菌门（Proteobacteria）、厚壁菌门（Firmicutes）;而属水平结果不同,肠道内容物样本中优势菌属包括Streptophyta、芽孢杆菌属（Bacillus）、杆菌属（Bacillaceae_unclassified）、气单胞菌属（Aeromonas）及弧菌属（Vibrio）,表皮粘液样本中优势菌属包括Streptophyta、气单胞菌属（Aeromonas）、杆菌属（Bacillaceae_unclassified）、香味菌属（Myriudes）、假单胞菌属（Gemmobacter）及弧菌属（Vibrio）。Heatmap热图结果提示,不同微生物菌群结构发挥出不同生物学功能,其中未分类杆菌属、气单胞菌属、弧菌属、假单胞菌属等条件性致病菌的存在均可能导致病害的发生。因此,揭示表皮粘液和肠道内容物样本中微生物的多样性及主要病原菌属的特征对大泷六线鱼健康养殖和疾病防控具有一定的指导意义。     

小黑山岛人工鱼礁区许氏平鲉和大泷六线鱼的营养生态位研究

以小黑山岛人工鱼礁区的2种典型恋礁鱼类——许氏平鲉(Sebastes schlegelii)和大泷六线鱼(Hexagrammos otakii)为研究对象,利用碳、氮稳定同位素技术分析了其在2016年春秋两季的生态位重叠及宽幅变化情况。许氏平鲉的δ~(13)C值在春季显著大于大泷六线鱼,而在秋季则无明显差异;δ~(15)N值在春秋两季均显著大于大泷六线鱼。频率分布方面,许氏平鲉的δ~(13)C值频率分布范围始终大于大泷六线鱼,而其δ~(15)N值频率分布的季节变动幅度小于大泷六线鱼,表明许氏平鲉具有更广泛的食物来源、占据较为稳定的营养级层次,大泷六线鱼则具有明显的摄食选择性且所居营养级层次波动剧烈。此外,许氏平鲉与大泷六线鱼仅在秋季出现营养生态位的重叠,表明在人工鱼礁区群落中许氏平鲉与大泷六线鱼之间存在种间食物竞争;而许氏平鲉春秋两季的营养生态位宽幅均大于大泷六线鱼,说明许氏平鲉较大泷六线鱼对食物资源的利用和竞争能力更强。     

Histological observations on the pituitary gland and the glomerular body of the larvae of the marine teleost,Hexagrammos otakii

Summary In the larvae of the marine teleost, Hexagrammos otakii, the prolactin, ACTH, STH and pars-intermedia cells as well as the neurohypophysis and glomerular body showed no histological change at the time of hatching. These cells or organs do not seem to be specifically involved in the mechanisms of adjustment to the hypertonic osmotic stress at this time. The size of the nuclei of the prolactin cells increased in fresh-water (F. W.) and that of the ACTH cells decreased in 2/3, 1/2 and 1/3 sea-water (S.W.). The amount of chrome-alum haematoxylin-positive material in the neurohypophysis of fish immersed in 1/2 S.W., 1/3 S.W. and F.W. was less than that of the control fish. There was a difference in the glomerular ratio between the fish kept in F. W. and control fish. And the red blood cells in the glomerulus of the larvae kept in 1/2 and 1/3 S.W. apparently increased in number in comparison with the control fish.The author wishes to express his gratitude to Professor Hideshi Kobayashi for his valuable guidance during the course of this study. The author is indebted to Dr. Masaaki Inoue, Kanagawa Prefectural Fisheries Experimental Station, for supplying the eggs of Hexagrammos.     

Maintenance of species boundaries despite rampant hybridization between three species of reef fishes (Hexagrammidae): implications for the role of selection

Hybridization and introgression are antagonistic to the process of speciation. If hybrids are viable and backcross, introgression will slow or prevent the evolution of reproductive isolation between populations. If species hybridize upon secondary contact, introgression will ultimately erode species boundaries. If hybridization is rampant and gene flow is high, the proportion of hybrids will approach values expected with random mating, and introgression will overcome species boundaries, homogenizing populations. Alternatively, if species are genetically distinct, the proportion of hybrids would be significantly less than expected with random mating, gene flow would be interrupted by selection against hybrids, and inviability or sterility of F ₁ hybrids or backcrosses would be expected. Here, we investigate a system with characteristics expected by both of these opposing scenarios. Hybridization occurs between three species of reef fishes in the genus Hexagrammos at unexpected high frequencies in a zone of distributional overlap. Backcrossed individuals are detected, indicating F ₁ hybrids are viable and capable of reproducing. Yet, these species are genetically distinct at multiple loci. To study this apparent paradox, we estimate the relative proportions of hybrids, patterns of symmetry, inviability, and cytonuclear disequilibria using one mitochondrial and two nuclear markers. We invoke selection against hybrids, at various life history stages, in the maintenance of species boundaries in this system.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 135–147.     

Isolation and characterization of nine polymorphic microsatellite loci of the kelp greenling, Hexagrammos decagrammus, a temperate reef fish

Nine polymorphic microsatellite loci were developed and characterized for the temperate reef fish species, Hexagrammos decagrammus (kelp greenling). The number of alleles varied from three to 22 in a sample of 22 individuals from one population. Expected heterozygosities ranged from 0.354 to 0.979. These microsatellites allow us to investigate reproductive success of individuals, alternative mating strategies as well as population structure and metapopulation dynamics of this species.     

基于线粒体DNA序列探讨斑头鱼分类地位

测定了斑头鱼Agrammus agrammus和大泷六线鱼Hexagrammos otakii的线粒体COⅠ、Cyt b和16S rRNA基因的部分序列,结合从GenBank中获得的六线鱼属3种的同源序列,以单鳍多线鱼Pleurogrammus monopterygius为外群,运用邻接法(NJ)、最大简约法(MP)和贝叶斯法(BI)构建了分子系统树。同时联合了3个基因片段序列,运用贝叶斯联合模型综合探讨了六线鱼类的系统发育关系。结果显示:除16S rRNA基因外,其余2个基因片段以及联合模型所构建的系统树拓扑结构完全一致,即斑头鱼与大泷六线鱼亲缘关系最近,应归为六线鱼属,拉丁学名应为Hexagrammos agrammus。Cyt b基因片段序列分析结果显示,斑头鱼和大泷六线鱼分歧时间约为175万年。结合形态学研究资料,支持将斑头鱼归为六线鱼属的观点,斑头鱼和大泷六线鱼亲缘关系最近,属于六线鱼科中分化较晚的种类。     

基于宏基因组测序技术揭示大泷六线鱼肠道微生物特征北大核心

对大泷六线鱼不同生长期肠道微生物进行分析。【目的】基于宏基因组学技术揭示其肠道微生物变化特征及其与营养的联系。【方法】对大泷六线鱼仔鱼、稚鱼和幼鱼肠道微生物样本进行HiSeq高通量测序,分析菌群结构,比较微生物群落的多样性,探究生长过程中肠道微生物的相互演替及功能关系。【结果】门水平上,鱼肠道微生物在生长过程中优势菌门变形菌门(Proteobacteria)递减,而厚壁菌门(Firmcutes)递增;属水平上,仔鱼期的弧菌属(Vibrio)(37.8%)、稚鱼期的发光杆菌属(Photobacterium)(77.8%)、幼鱼期的乳酸菌属(Lactococcus)(42.5%)占优势,微生物群落组成发生显著变化;且仔鱼期的多样性高,幼鱼期的丰富度高;物种差异也呈现着与生长特征的相关性,幼鱼期差异标志物是厚壁菌门、芽孢杆菌纲(Bacilli)、乳酸杆菌目(Lactobacillales)、链球菌科(Streptococcaceae)、乳球菌属(Lactococcus)和乳酸乳球菌(Lactococcus lactis);稚鱼期差异标志物是发光菌属、托鲁尼发光菌(Photobacterium toruni);仔鱼期差异标志物是Phaeobacter inhibens、Colwellia aestuarii和Colwellia polaris等。宏基因组功能水平分析显示,KEGG数据统计代谢功能占优势,随生长呈现递增趋势,鱼肠道微生物群在碳水化合物代谢、氨基酸代谢、核苷酸代谢、能量代谢,以及辅助因子和维生素代谢中起着重要作用;从蛋白注释功能上也呈现了类似的结果,碳水化合物代谢(3350)和氨基酸代谢(2424)占代谢通路主要组成部分。功能差异分析表明,随着生长变化,微生物功能逐渐适应机体和环境需求,稚鱼期差异主要体现在能量代谢和糖降解功能;仔鱼期差异显著的是细胞的生长、死亡和凋亡功能,主要体现在光合作用方面;幼鱼期主要体现是二级代谢物的生物合成,其次是糖酵解和糖异生等碳水化合物代谢等。【结论】大泷六线鱼仔、稚、幼不同生长期肠道微生物结构存在显著差异,生长发育改变肠道微生物菌群的功能,采用差异物种和差异功能综合判定生长所需的营养,有助于提高养殖效益,为绿色健康生态养殖提供理论基础。