中华绒螯蟹MSTN基因SNPs多态性及与生长性状的关联分析

为研究中华绒螯蟹(Eriocheir sinensis)肌肉生长抑制素基因(myostatin, MSTN)的多态性及其与生长性状的相关性, 对中华绒螯蟹3个群体(育种群体、大赛群体、野生群体)共321个个体MSTN基因的多态性进行筛选, 发现该基因的第1外显子存在3个多态性SNP位点(S1: C714T; S2:G729A; S3:G753T), 均为处于Hardy-Weinberg平衡(P>0.05)的中、高度多态性位点。利用一般线性模型分析3个位点及其基因型组合与生长性状的相关性, 发现S1位点对中华绒螯蟹的体重和壳长等生长性状有显著影响(P≤0.05), 而其余2个位点与生长性状无显著关联性。结果表明S1位点的TT基因型对中华绒螯蟹的生长最为有利, 可作为分子标记辅助育种的候选标记。     

中华鳖(Trionyx sinensis)微卫星标记与生长性状的相关分析

利用筛选到的25个微卫星标记,以中华鳖极大、极小两个群体共120个个体为实验材料,分析这些微卫星标记与体重、背甲长、背甲宽、体高、腹甲长及腹甲宽之间的相关性。结果表明:有3个位点与生长性状的相关性达到显著或极显著水平(p0.05或p0.01),其中位点LTF1与体重、背甲长、背甲宽、腹甲长、腹甲宽、体高均极显著相关;位点LTR87与体重、背甲长、和腹甲宽显著相关;位点LT8与体重、体高、腹甲长、腹甲宽显著相关。将同一性状不同基因型之间进行多重比较,结果显示位点LTF1中的BE型,位点LTR87中的BB型,以及位点LT8中的CF型、BC型、AC型、CC型具有明显的生长优势,可作为辅助育种的参考标记。     

湖羊、东湖杂种羊POMC基因外显子3单核苷酸多态性及其与生长性状的关联分析

阿黑皮素原(Pro-opiomelanocortin, POMC)在动物采食和能量平衡调控中发挥重要作用, 文章对绵羊POMC基因外显子3进行扩增和测序, 筛选多态性位点, 并分析多态位点与湖羊和东弗里生×湖羊杂种羊生长性状的相关性。测序后发现湖羊POMC基因外显子3有2个单碱基突变(g.273 T/C和g.456 G/A), 根据273位点处发生的T/C突变, 建立PCR-RFLP分析方法, 并对162只湖羊和130只东湖杂种羊进行检测分析。结果发现, 在湖羊群体中检测到TT(0.469)、TC(0.438)和CC(0.093)3种基因型, 而在东湖杂种羊群体中仅检测到TT(0.754)和TC(0.246)两种基因型。POMC基因外显子3的273位点多态性与生长性状的相关性研究结果显示：湖羊群体中CC基因型个体的2月龄断奶重、4月龄尻高及TC基因型个体4月龄体长和管围均显著高于TT型个体(P<0.05); CC基因型个体的4月龄重、6月龄重极显著高于TT和TC基因型个体(P<0.01); CC基因型个体的4月龄体高和体长极显著高于TT型个体(P<0.01), 且显著高于TC基因型个体(P<0.05)。此外, CC型个体的管围极显著高于TT基因型个体(P<0.01)。东湖杂种羊群体中TC基因型个体的2月龄断奶重、4月龄重及4月龄体高、体长、胸深和管围都显著高于TT型个体(P<0.05), TC型个体的6月龄重极显著高于TT型个体(P<0.01)。研究结果表明, POMC基因外显子3与绵羊生长性状相关, C等位基因对体重及体尺性状的增加更有利。该结果为进一步探讨POMC基因作为绵羊生长性状的辅助选育标记奠定了基础。     

大黄鱼快长相关微卫星标记的筛选与验证

为了筛选与大黄鱼生长性状紧密相关的分子标记,并对这些标记的有效性进行鉴定,研究以大黄鱼家系和群体为材料,经标记筛选、两次验证共三个步骤,找到2个与大黄鱼生长性状紧密相关的微卫星标记:LYC0088和LYC0143,其中LYC0088与体高、体质量均极显著相关（P0.01）,与体长显著相关（P0.05）,LYC0143与体长和体质量显著相关（P0.05）,与体高的相关性极显著（P0.01）。LYC0088与LYC0143位点的优势等位基因分别为E、A,优势等位基因型均为AB,优势等位基因型组合为AB/AB,两个位点呈加性效应。该结果为开展大黄鱼分子标记辅助育种提供了有价值的遗传标记。       

三个绵羊品种LHX3基因多态性与生长性状的关联分析

寻找与绵羊生长性状有关的分子标记,以期为绵羊的分子育种提供理论依据。通过琼脂糖凝胶电泳和一代测序技术,在滩羊(TS)、小尾寒羊(STHS)和兰州大尾羊(LFTS)的LHX3基因中检测到了29 bp片段的插入型(AA)、插入/缺失型(AB)以及缺失型(BB)3种基因型,对3个不同品种绵羊的LHX3基因进行遗传多态性分析,并通过一般线性模型分析了3种基因型与3个品种绵羊不同生长性状的相关性。3个品种绵羊LHX3的多态信息含量(PIC)均为0.25 PIC≤0.5,呈中度多态,表明该位点的遗传变异相对较高。LHX3基因型影响3个品种绵羊的一个或多个生长性状,其中LHX3基因型与滩羊的体长(BL)、体重(BW)、胸深(ChD)和管围(CaC)显著相关(P 0.05),且缺失型基因型的生长性状优于插入型基因型和插入/缺失型基因型绵羊;小尾寒羊的缺失型基因型的胸围(ChC)、胸深(ChD)和管围(CaC)显著高于插入型基因型和插入/缺失型基因型绵羊(P 0.01);兰州大尾羊的缺失型基因型的胸围(ChC)、十字部高(HW)、体长(BL)、体重(BW)和管围(CaC)显著高于插入型基因型和插入/缺失型基因型绵羊(P 0.01)。由此可见在绵羊分子育种中,LHX3中29 bp的缺失型可作为绵羊选育的DNA标记位点。     

企鹅珍珠贝微卫星标记与生长性状的相关性研究

研究利用5个高度多态性的微卫星标记,对500个企鹅珍珠贝(Pteria penguin)的4个生长性状进行了关联分析。结果显示, QEB-D15和CL-232两个微卫星标记与企鹅珍珠贝的壳宽呈极显著相关(P<0.01);位点QEBD15基因型是239/263的个体壳宽为最大值,基因型是239/273的个体壳宽为最小值,推测263 bp等位基因与壳宽之间存在正相关关系,而273 bp等位基因与壳宽之间存在负相关关系;位点CL-232基因型为157/174的个体壳长、壳宽、总重的均值较同一位点的其他基因型均为最大值,该基因型推测为优势基因型;而基因型为177/192的个体壳长、壳宽、壳高和总重的均值较同一位点的其他基因型均为最小值,推测该基因型为劣势基因型,上述结果可为企鹅珍珠贝分子标记辅助选择育种提供理论依据和参考。     

罗氏沼虾转录组SSR标记筛选及其与体质量相关性分析

研究通过转录组测序对罗氏沼虾(Macrobrachium rosenbergii)SSR标记进行了发掘, 获得SSR位点18592个。随机选取了63个SSR位点设计引物并利用10个个体进行多态性位点筛选, 共获得31个具有多态的SSR标记, 利用其中19个SSR标记对全同胞家系群(FS)119尾虾及孟加拉F3代野生群(MJL)199尾虾的群体遗传多样性进行分析, 并对SSR位点与体质量性状进行关联性分析。结果表明: FS群体共检测到40个等位基因, 平均等位基因数为2.1053, 平均观测杂合度0.4525, 平均期望杂合度0.3804, 平均多态信息含量0.3076, 处于中度遗传多态水平; MJL群体共检测到65个等位基因, 平均等位基因数为3.4211, 平均观测杂合度0.4105, 平均期望杂合度0.4496, 平均多态信息含量0.3882, 处于中度遗传多态水平。 19个SSR位点与FS群体体质量没有相关性(P>0.05), 而在MJL群体中, 4个SSR位点与体质量显著相关(P<0.05)。对差异显著的位点进行不同基因型体质量性状的多重比较, MR28位点277/285基因型体质量均值极显著高于277/289和285/285基因型(P<0.01), 显著高于285/289、273/289、270/273和285/293基因型(P<0.05); MR32位点266/266和266/270基因型体质量均值显著高于270/270基因型(P<0.05); MR34位点210/214基因型体质量均值显著高于210/210和214/214基因型(P<0.05); MR45位点174/190基因型体质量均值显著高于182/182和182/190基因型(P<0.05)。研究结果为罗氏沼虾分子标记辅助育种奠定了基础。     

闽江水系绒螯蟹的表型性状差异与分子遗传差异的比较与分析

表型性状差异(differentiation in phenotypictraits,PST)和分子遗传差异(differentiation at neutral molecular markers,FST)是近期进化生物学的研究热点之一。闽江水系是我国中华绒螯蟹与合浦绒螯蟹的主要混杂地域,是研究绒螯蟹遗传与进化的理想地之一。为探讨闽江水系绒螯蟹的PST和FST,以2009和2010年度闽江水系的133个绒螯蟹样本为材料,进行了14个表型数量性状差异分析和6个微卫星标记的遗传差异分析。结果发现:除3个表型性状不存在显著差异外,其他表型性状在不同年份间均存在极显著差异(P<0.01);2009年绒螯蟹的平均期望杂合度极显著高于2010年绒螯蟹(P=0.008),而平均等位基因丰富度、观测杂合度和近交系数均不存在显著差异(P=0.136～0.675);年份间的平均FST为0.1429;通过对PST与FST的比较发现,除第二步足掌节长度(F2)性状外,其他表型数量性状的PST值均高于FST值,表明这些性状均受到了较明显的选择压力。该文研究结果为绒螯蟹的分子进化研究积累了资料,也为其他水产生物的PST和FST比较研究提供了参考。     

郏县红牛ZAG基因多态性与生长性状的相关性

摘要: ZAG基因的功能主要是促进脂肪分解, 减少脂肪含量。文章利用PCR-SSCP和DNA测序技术研究了145头郏县红牛ZAG基因编码区4个位点(Z1、Z2、Z3、Z4)的多态性, 发现Z1、Z3、Z4 位点存在SSCP多态。对不同SSCP带型的对应片段进行了测序分析, 共发现6个新的SNP多态位点(C115T、A3257G、A4013G、T4027C、C4032T、T4120C)。Z3位点处于Hardy-Weinberg平衡状态, Z1、Z4 位点处于非平衡状态。不同基因型与生长发育性状的相关性分析显示, Z4位点上, AC基因型个体的体斜长、胸围、管围、体重指标显著(P<0.05)或极显著(P<0.01), 大于AA、AB基因型个体, 暗示该位点有可能作为郏县红牛生长性状标记辅助选择的标记之一。     

早胜牛类群A-FABP基因SNPs及其与胴体品质和肉质性状的相关性分析

研究早胜牛类群A-FABP基因多态性及其与胴体品质和肉质性状的相关性。采用PCR-SSCP方法对5个早胜牛类群(庆阳类群、平凉类群、南德温与庆阳类群杂种、西门塔尔与平凉类群杂种、秦川牛与平凉类群杂种)的A-FABP基因进行多态性分析,分析基因型与胴体品质和肉质性状的相关性。结果显示,A-FABP基因第三外显子区存在c.408GC的突变,并检测到3种基因型GG、GC和CC。胴体性状相关分析表明,GG基因型的胴体重显著低于CC基因型(P0.05);GG基因型屠宰率极显著低于GC基因型(P0.01),显著低于CC基因型(P0.05);GG基因型净肉率显著低于GC基因型(P0.05);GG基因型的眼肌面积显著低于GC和CC基因型(P0.05)。肉质性状相关分析表明,GG基因型失水率显著高于CC基因型个体(P0.05);GG基因型剪切力极显著高于GC和CC基因型(P0.01);GG基因型蒸煮损失和pH均显著高于GC基因型(P0.05),极显著高于CC基因型(P0.01)。A-FABP基因突变位点可作为胴体性状和肉质性状遗传标记。     

长江口中华绒螯蟹放流亲蟹的繁殖力评估

在长江口中华绒螯蟹亲蟹生殖洄游期间, 通过研究中华绒螯蟹放流群体和自然群体繁殖力随壳宽的变化规律, 比较放流群体和自然群体繁殖力的差异, 从而评估人工增殖放流亲蟹的繁殖力。结果显示, 随着壳宽的增大, 中华绒螯蟹放流群体和自然群体的繁殖力都显著增加(P<0.05)。在相同壳宽范围内, 放流群体和自然群体的繁殖力之间没有显著差异(P>0.05)。回归分析显示, 放流群体繁殖力(F)与壳宽(CW)呈幂函数关系: F=3.979CW6.208(R2=0.822);自然群体F与CW呈幂函数关系: F=1.696CW6.636(R2=0.673)。协方差分析显示, 放流群体与自然群体F与CW的两条曲线在显著性为0.05时拟合较好。研究结果表明, 放流群体与自然群体的繁殖力与壳宽之间无显著性差异, 推断放流亲蟹能够适应长江口天然水域环境, 并与自然群体的繁殖力水平相当。     

Molecular genetic structure and evolution in native and colonized populations of the Chinese mitten crab, Eriocheir sinensis

Chinese mitten crab (Eriocheir sinensis), a native species in China, has populated Continental Europe and North America since 1912. In this paper, the nucleotide variation in the fragments of mitochondrial COII (693 bp), Cytb (766 bp), and nucleotide ITS (706 bp) was analyzed in native (Yantgze, Yellow, and Liaohe Rivers in China) and colonized (Elbe, Rhine, and Thames Rivers in Europe, and San Francisco Bay in North America) populations of the Chinese mitten crab. The major findings are as follows. First, the genetic variability in the native populations is higher than that in the colonized European and North American populations, with the exception of the Elbe River population, which possesses a similar level of variability with the native populations. Second, a remarkable loss of singletons has been associated with the colonization of Chinese mitten crabs. Third, the AMOVA and F _ST results demonstrate that there are no significant genetic differentiations among the populations from the three continents, but there is a significant differentiation between pairwise populations within and among continents. Fourth, it is found that expansion-drift and gene flow pattern are involved in the European populations. The neutrality test and R ₂ statistics suggest that a moderate founder population exists in the colonized populations, and only the Yangtze River population has undergone a recent population expansion. Finally, the results demonstrate that the European populations originate from multiple rivers in China on multiple occasions. The San Francisco population originates from both the native Chinese populations and the colonized European populations, most likely the Thames population.     

以精子为载体把外源DNA导入中华绒螯蟹的初步研究

The study of crustacean genetics and breeding has been received more and more at-tention due to the rapid development of the shrimp and crab aquaculture.Chromosomesetmanipulation on shrimp and crab[1 ] [2 ] ,and the work on transgenic shrimp[3] [4] have gotsome progress.However,there is no transgenic research reported on crab to our knowl-edge.The purpose ofthis paper is to study the feasibility of using sperm as vector to in-troduce foreign DNA into Chinese mitten crab ( Eriocheir sinensis …     

Microsatellite analysis of genetic diversity and population structure of Chinese mitten crab （Eriocheir sinensis）

Chinese mitten crab (Eriocheir sinensis) has higher commercial value as food source than any other species of Eriocheir in China.To evaluate the germplasm resources and characterize the genetic diversity and population structure of the crabs in different water systems,two stocks and two farming populations were assessed with 25 polymorphic microsallite loci available in public GenBank.Basic statistics showed that the average observed heterozygosity (Ho) amongst populations ranged from 0.5789 to 0.6824.However,a remarkable presence of inbreeding and heterozygote deficiencies were observed.To analyze population structure,pairwise FST coefficients explained only ～10.3% variability from the subdivision of mitten crab populations,the remaining variability stems from the subdivision within subpopulations.Although the four populations had slight differentiation,different allelic frequencies resulted in distinct population structures.Two stocks and one farming population were clustered together to the phylogenetic branch of Yangtze crab,with an approximate membership of 95%.Whereas,another fanning population was clustered singly to the phylogenetic branch of the Liaohe crab,with a membership of 97.1%.The tests for individual admixture showed that Yangtze crab had probably been contaminated with individuals from other water systems.Genetic relationships between populations also supported the conclusion that Yangtze crab and Liaohe crab had different gene pools in spite of the origins of the same species.     

Characterization of two C-type lectin-like domain (CTLD)-containing proteins from the cDNA library of Chinese mitten crab Eriocheir sinensis

Chinese mitten crab Eriocheir sinensis is one of the most important aquaculture crustacean species in China. A cDNA library was constructed from mixed tissues of E. sinensis challenged with LPS. Eight genes involved in immune response were identified from 319 single colonies. Among them, two different C-type lectin-like domain (CTLD)-containing proteins were firstly identified in Chinese mitten crab. The full-length cDNA sequences of two C-type lectin-like domain (CTLD)-containing proteins named EsCTLDcp-1 and EsCTLDcp-2 were cloned by 5' RACE. The deduced amino acid sequences of EsCTLDcp-1 and EsCTLDcp-2 possessed several conserved features of C-type lectin subfamily. The tissue distribution of EsCTLDcp-1 and EsCTLDcp-2 was examined by Real-time PCR. In the normal Chinese mitten crab, the expression of EsCTLDcp-2 was detected in all tested tissues such as haemolymph, muscle, intestine, gill, heart, gonad and hepatopancreas, whereas in muscle, intestine, gill, heart and hepatopancreas for EsCTLDcp-1. The highest expressions of EsCTLDcp-1 and EsCTLDcp-2 were both observed in hepatopancreas. LPS significantly induced the expression of EsCTLDcp-1 and EsCTLDcp-2 in the hepatopancreas at the different time points. The induced fold change of EsCTLDcp-1 and EsCTLDcp-2 increased significantly from 2 h for EsCTLDcp-1 and 4 h for EsCTLDcp-2, and reached a maximum at 12 h, then dropped at 24 h. A differential pattern was found in Chinese mitten crab challenged with Chinese mitten crab pathogen Aeromonas hydrophila. The expression of EsCTLDcp-1 increased significantly at 2 h post-challenge crabs with A. hydrophila, then decreased at 4 h and 8 h, after that increased at 12 h and 24 h. The expression of EsCTLDcp-2 was decreased at the all time points. All these data suggest a differential role of EsCTLDcp-1 and EsCTLDcp-2 in the crab innate immune response to bacterial infection.     

湖泊放养长江水系中华绒螯蟹的性成熟规律研究

于8－11月份,结合中华绒螯蟹捕捞期,即生死洄游期的到来,通过性腺发育的组织学和细胞学观察,重点观察了长江下游安徽杨赛湖等人工放养长江水系中华绒螯蟹的性成熟规律。结果表明：①在性成熟时期,性腺发育与肝脏变化极为密切,肝脏指数逐渐下降,而性腺指数逐渐上升;②雌、雄蟹的性成熟存在规律性差异,8－9月份,雄蟹的性腺指数和性／肝指数均高于雌蟹,而10－11月份,雌蟹的性腺指数和性／肝指数均高于雄蟹;③经性腺的组织学和细胞学观察,雄蟹的性腺发育略早于雌蟹;④洄游高峰期的出现是河蟹性细胞走向成熟的外在表现。作者建议把肝脏指数7.5作为捕捞长江水系河蟹最佳时机的指标。     

中华绒螯蟹幼蟹温度选择与偏好研究

研究通过利用自动化的电子穿梭系统研究长江野生中华绒螯蟹幼蟹的行为参数对温度变化的响应, 进行了Ⅰ组8℃和14℃实验组、Ⅱ组14℃和21℃实验组、Ⅲ组21℃和28℃实验组、Ⅳ组28℃和35℃实验组共4个实验组。实验表明中华绒螯蟹幼蟹的最佳偏好温度在28℃。幼蟹会加速逃离不适温度区域, 且偏离温度越高游泳速率越高, 温度和游泳速率拟合方程: y=0.0027x2–0.1045x+1.5875, R2=0.8615, 昼夜(P>0.05)和雌雄性别(P>0.05)差异对温度的偏好选择未见明显影响。研究为中华绒螯蟹养殖、利用及野外环境下种群保护与调控管理提供科学依据。     

Maintaining Economic Value of Ecosystem Services Whilst Reducing Environmental Cost: A Way to Achieve Freshwater Restoration in China

Freshwater fisheries are central to food security in China and this remains one of the most important priorities for the growing human population. Thus, combining ecosystem restoration with economics is pivotal in setting successful conservation in China. Here, we have developed a practical management model that combines fishery improvement with conservation. For six years, a ban on fertilizer and a reduction of planktivorous fish stocking along with the introduction of both mandarin fish Siniperca chuatsi and Chinese mitten crab Eriocheir sinensis was apparent in Wuhu Lake, a highly eutrophic lake located in the middle reaches of the Yangtze River. Annual fish yield decreased slightly after the change in management, whereas fisheries income increased 2.6 times. Mandarin fish and Chinese mitten crab accounted for only 16% of total fisheries production but for 48% of total fisheries income. During this six year period, water clarity increased significantly from 61 cm to 111 cm. Total nitrogen, total phosphorus and chlorophyll decreased significantly from 1.14 to 0.84 mg/L, 0.077 to 0.045 mg/L, and 21.45 to 11.59 μg/L respectively, and macrophyte coverage increased by about 30%. Our results showed that the ecological status of shallow lakes could be rapidly reversed from eutrophic to oligotrophic using simple biomanipulation, whilst maintaining fisheries economic value. It also offers a better approach to shallow fisheries lake management in Asia where traditionally the stocking of Chinese carp and use of fertilizers is still popular.     

四种植物蛋白对中华绒螯蟹幼蟹生长性能、氨基酸沉积率和抗氧化酶活性的影响

为了筛选适宜于养殖中华绒螯蟹幼蟹的饲料植物蛋白源,探究不同植物蛋白源饲料对幼蟹生长性能、氨基酸沉积率和抗氧化性能等方面的影响,以50%的鱼粉配制基础饲料（记为FM）,分别采用30.5%发酵豆粕、32.5%豆粕、28%棉粕和39%菜粕替代基础饲料中鱼粉总量的50%,配制成4种等氮等能的饲料（分别记为FSBM、SBM、CSM和RSM）,投喂初始体重为（0.249±0.003）g的中华绒螯蟹幼蟹8周。结果表明:（1）与FM组相比,FSBM、SBM和CSM组的增重率、特定生长率、饲料系数、蛋白质效率和蛋白质沉积率均没有显著性差异;RSM组的增重率与FM组相比差异不显著（P>0.05）,但显著低于SBM组（P < 0.05）,而其饲料系数则显著高于FM、FSBM及SBM组（P < 0.05）,蛋白质效率显著低于其他各组（P < 0.05）,蛋白质沉积率显著低于SBM和CSM组（P < 0.05）。（2）不同植物蛋白组的总必需氨基酸沉积率和FM组相比差异不显著（P>0.05）,而RSM组总必需氨基酸沉积率显著低于FSBM和CSM组（P < 0.05）。（3）与FM组相比,不同植物蛋白组蟹的血清和肝胰腺中超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-PX）活性和肝胰腺丙二醛（MDA）含量并没有显著的影响,而RSM组血清丙二醛（MDA）含量显著的高于其他各组（P < 0.05）。结果表明,在幼蟹饲料中,豆粕、发酵豆粕和棉粕替代基础配方中鱼粉的50%后并未对幼蟹的生长性能、氨基酸沉积率及抗氧化能力造成负面的影响,发酵豆粕、豆粕和棉粕可以作为替代鱼粉的适宜蛋白源,且添加水平约在30%左右。菜粕替代后降低了饲料的利用和氨基酸沉积效率,这可能是由于菜粕的蛋白质消化率低、含有相应的抗营养因子和添加水平过高所致,建议使用前应适当进行脱毒处理,并与或和其他植物蛋白配伍使用。     

Phylogenetic analysis of intestinal bacteria in the Chinese mitten crab (Eriocheir sinensis)

AIMS: To identify the dominant intestinal bacteria in the Chinese mitten crab, and to investigate the differences in the intestinal bacteria between pond-raised and wild crabs. METHODS AND RESULTS: The diversity of intestinal bacteria in the Chinese mitten crabs was investigated by denaturing gradient gel electrophoresis (DGGE) fingerprinting, 16S rRNA gene clone library analysis and real-time quantitative PCR. The principal component analysis of DGGE profiles indicated that substantial intersubject variations existed in intestinal bacteria in pond-raised crab. The sequencing of 16S rRNA genes revealed that 90-95% of the phylotypes in the clone libraries were affiliated with Proteobacteria and Bacteroidetes. Some genera were identified as unique in wild crabs and in pond-raised crabs, whereas Bacteroidetes was found to be common in all sampled crab groups. Real-time quantitative PCR indicated that the abundance of Bacteroides and the total bacterial load were approximately four-to-10 times higher in pond-raised crabs than in wild crabs. A significant portion of the phylotypes shared low similarity with previously sequenced organisms, indicating that the bacteria in the gut of Chinese mitten crabs are yet to be described. CONCLUSIONS: The intestinal bacteria of pond-raised crabs showed higher intersubject variation, total diversity and abundance than that observed in wild crabs. The high proportion of the clones of Proteobacteria and Bacteroidetes in the clone library is an indication that these bacteria may be the dominant population in the gut of the Chinese mitten crab. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated obvious differences in the intestinal bacterial composition of pond-raised crabs and wild crabs. This knowledge will increase our understanding of the effects of aquaculture operations on bacterial community composition in the crab gut and provide necessary data for the development of probiotic products for crab cultivation.