基于线粒体COⅠ基因DNA条形码的中国鲚属物种有效性分析

分析了150尾刀鲚Coilia nasus、湖鲚C.nasus taihuensis、短颌鲚C.brachygnathus、七丝鲚C.grayii及凤鲚C.mystus个体的COⅠ基因DNA条形码序列变异。结果显示,150条COⅠ基因条形码序列包含63种单倍型,单突变位点主要集中在100bp和600bp附近。刀鲚、短颌鲚和湖鲚群体间的遗传距离在0.253%～0.557%之间,显著低于COⅠ基因DNA条形码鉴别不同物种2%的遗传距离阈值,表明这3个群体应为同一物种。但是凤鲚两群体间的遗传距离为5.08%,大于2%的鉴别阈值,显示凤鲚两群体可能达到了种或亚种级差异水平。以日本鳀Engraulisjaponicus为外群,用邻接法、最大简约法和最大似然法构建了分子系统树显示,刀鲚、湖鲚和短颌鲚群体聚在一起,未能各自形成单系;凤鲚根据地理分布聚为两支;七丝鲚则聚成单系。研究表明COⅠ基因条形码技术可用于我国鲚属物种的鉴定。     

从线粒体控制区全序列变异看短颌鲚和湖鲚的物种有效性

经克隆测序获得我国七丝鲚(Coilia grayii)、凤鲚(C. mystus)、刀鲚(C. nasus)和短颌鲚(C. brachygnathus)以及太湖湖鲚(C. nasus taihuensis)等4个种和1亚种32尾个体的mtDNA D-loop区全序列, 以日本鳀(Engraulis japonicus)和秘鲁鳀(E. ringens)为外类群构建了中国鲚属的分子系统发育树, 并讨论了短颌鲚和湖鲚的物种有效性。结果显示, 七丝鲚的D-loop区全序列长1,208 bp, 凤鲚1,279–1,361 bp, 刀鲚1,252–1,290 bp, 短颌鲚1,214–1,252 bp, 湖鲚1,252–1,442 bp, 除七丝鲚外的其他种类个体间均表现出序列长度的多态性。短颌鲚、刀鲚和湖鲚三者间的平均K 2-P遗传距离仅为0.011–0.020, 明显小于它们与凤鲚、七丝鲚及外类群间的遗传距离(0.051–0.349)。以邻接法和最大简约法构建的系统发育树表明, 刀鲚、短颌鲚及湖鲚均未各自构成单系, 而是共同构成一个单系群, 三者并未发生显著分化。研究表明, 短颌鲚和湖鲚为刀鲚的淡水生态型种群, 并非有效物种。系统发育分析表明, 中国鲚属3个有效物种间以凤鲚最为原始, 刀鲚和七丝鲚为姐妹群, 处于较进化的位置。推测凤鲚可能是鲚属祖先种最早从起源中心扩散到西北太平洋的后裔, 而刀鲚和七丝鲚则是凤鲚在演化过程中分别适应寒冷和温暖气候而分化出的物种。     

刀鲚胚胎及胚后发育早期脂肪酸组成变化

为掌握刀鲚(Coilia nasus)胚胎及胚后发育早期的脂肪酸变化规律,采用生化分析手段对刀鲚的胚胎(原肠期,受精后7～9 h)、0日龄仔鱼(初孵仔鱼)、3日龄仔鱼和5日龄仔鱼(开口前)的脂肪酸组成和含量进行了检测分析。结果显示,刀鲚发育早期的总脂占干物质的相对含量均较高(53.10%～60.97%),干物质的总脂相对含量随个体发育显著降低,单个个体的总脂含量随个体发育呈现剧烈下降趋势,数值从胚胎的43.62μg/ind剧烈下降到5日龄仔鱼的16.27μg/ind;水分含量随个体发育而升高。刀鲚发育早期上述4个时期的干样中检出6种饱和脂肪酸(SFA)、4种单不饱和脂肪酸(MUFA)和8种多不饱和脂肪酸(PUFA)。4个发育时期脂肪酸相对含量,C18:1n9c占绝对优势(50.39%～57.00%),C16:1丰富且稳定(13.77%～14.24%),C16:0也较丰富(7.45%～9.15%)。单不饱和脂肪酸(MUFA)比例占绝对优势(65.14%～72.26%),n-3与n-6系列多不饱和脂肪酸含量的比值(∑n3PUFA/∑n6PUFA)较小(1.78～2.38)。刀鲚胚胎孵化出膜期间,单个个体单不饱和脂肪酸(MUFA)实际减少程度较高,尤其是C18:1n9c(减少量为13.21μg/ind,减少比例达到55.49%)和C16:1(减少量和比例分别为3.30μg/ind和53.12%),而二十碳五烯酸(EPA)加二十二碳六烯酸(DHA)的减少程度较低(1.44μg/ind和38.41%),尤其是DHA(0.95μg/ind和36.52%)。然而,出膜后,仔鱼对单不饱和脂肪酸(MUFA)的利用相对较低(1.94μg/ind和14.17%),尤其是C18:1n9c(13.21μg/ind和12.41%)和C16:1(0.63μg/ind和21.81%);而对EPA+DHA利用相对较高(1.04μg/ind和45.10%),尤其是DHA(0.71μg/ind和42.61%)。研究表明,刀鲚胚胎优先蓄留EPA和DHA,仔鱼在摄食前大量利用EPA+DHA(特别是DHA),呈现出海水鱼类脂肪酸的利用特点。因此,建议在刀鲚亲本强化培育及产后培育中,增加投喂富含单不饱和脂肪酸(MUFA)(特别是C18:1和C16:1)的饵料,以加强刀鲚亲本的营养积累和产卵后亲本生理机能的恢复;在刀鲚育苗前期,要及时补充富含DHA和EPA的饵料,如,单胞藻、蛋黄等,以提高刀鲚仔鱼开口期间的成活率。     

长江刀鲚生殖洄游期间脂肪酸组成及含量变化分析

为探究长江刀鲚生殖洄游过程中脂肪酸组成及其含量变化规律,研究选择洄游距离、卵巢发育和规格大小3个影响因子设置梯度,对长江刀鲚肝胰腺、肌肉和卵巢的脂肪酸组成及含量进行实验分析。实验结果显示, 62尾雌性刀鲚3个组织均检测出28种脂肪酸,以单不饱和脂肪酸(MUFA)含量最高,大于各组织总脂肪酸含量的56.23%,各类脂肪酸中的C18:1、C16:0、C16:1、DHA和EPA含量较高,为主要脂肪酸。在生殖洄游过程中,刀鲚肝胰腺总脂肪含量随洄游距离的延长呈上升趋势,从崇明江段的(526.61±38.50) mg/g增加至安庆江段的(587.21±124.72) mg/g,而肌肉和卵巢总脂肪酸含量呈显著下降趋势,分别下降了33.03%和57.09%(P<0.05)。在各体长组中,肌肉总脂肪酸、SFA、MUFA和PUFA含量与体长呈正相关(P<0.05),而肝胰腺和卵巢总脂肪酸及各类脂肪酸含量与体长无显著相关性(P>0.05)。在卵巢发育过程中,刀鲚肝胰腺和肌肉总脂肪酸、MUFA和PUFA含量随卵巢由Ⅱ期发育至Ⅳ期均呈下降趋势,总脂肪酸含量分别减少了47.56%和22.40%,...     

太湖湖鲚生长特征和临界年龄的研究

湖鲚(Coilia ectenes taihuensis Yuanet Lin)是太湖鱼类优势种群,占太湖渔业总产的50%左右。为了探索湖鲚世代种群数量变动等生态特征,研究湖鲚的生长和临界年龄乃是一项重要的基础工作。作者曾于1983年作过初步探讨,并着重分析了临界年龄,为分析湖鲚合理开捕年龄与渔业管理提供科学依据。一、材料和方法1.材料(1)1983年1—12月每月定时在太湖8个采样点,用底拖网采集样本,底拖网的网口     

中国鲚属鱼类的矢耳石形态特征

分析了205尾分布于中国的4种2龄鲚属鱼类的矢耳石形态特征。结果显示,这4种鱼类的矢耳石都具有翼叶和基叶,但无后基叶和副基叶,中央突也不明显。背侧有脊突,叶形晶状突呈小三角形,仅限于腹侧。主凹槽明显,直管状,后端封闭。4种鱼矢耳石长轴长为体长的1.68%~2.82%,矢耳石重为体重的0.26‰~1.71‰;不论绝对重量或面积,均以七丝鲚和凤鲚的最大,刀鲚的次之,短颌鲚的最小,显现出与在海水中生活的时间呈正相关性。刀鲚和短颌鲚的矢耳石较轻薄,单位面积均重1.22~1.40mg/mm2;七丝鲚和凤鲚的较厚重,单位面积均重约1.86mg/mm2。矢耳石的长轴、短轴和单位重量等的变异系数,均要小于其体长特别是体重的变异系数,矢耳石形态的稳定性显著优于其身体形态的稳定性。     

基于矢耳石形态特征的中国鲚属鱼类种类识别

分析了中国鲚属鱼类七丝鲚、凤鲚、刀鲚和短颌鲚共4种205尾2龄鱼矢耳石的32个形态特征。对9个可量性状的主成分分析表明,反映矢耳石体积和基叶大小的第1主成分,以及与反映翼叶大小的第2主成分共同解释了总变异的91.2%,是种类判别的主要依据。对10个比例性状的逐步判别显示,4个种的平均正判率达95.6%,但交互验证结果却显示,刀鲚与短颌鲚间存在着20.1%的误判率,表现出与传统的依据外部形态分类和线粒体DNA控制区全序列分析的相似结果。这表明,短颌鲚并非有效种,而是刀鲚的淡水生态型种群,也预示着耳石形态分析在近缘种判别方面的良好应用前景。     

长江中下游刀鲚资源和种群组成变动状况及其原因

在长江中下游,刀鲚(Coilia ectenes)是著名的江海洄游型经济鱼类之一,为苏、皖等省沿江渔民重要捕捞对象,产量很高。但近年来其产量日趋下降,因而引起了广大渔民和有关方面的焦虑。关于长江中下游刀鲚资源和种群组成情况,在1973—1975年期间,长江水产研究     

长江安庆江段刀鲚耳石微化学及洄游生态学意义

刀鲚(Coilia nasus)属辐鳍鱼纲、鲱形目、鳀科,是我国长江下游一种传统的名贵经济鱼类。长江安徽江段为刀鲚的主要分布区之一,但近年来由于人类活动干扰、栖息地衰退及过捕等原因,资源量急剧下降。近期发布的《国家重点保护野生动物名录》水生野生动物调整方案已拟将刀鲚列入国家二级重点野生动物保护名录。为客观了解长江安庆江段刀鲚的生境"履历"及探讨其洄游史,利用X射线电子探针微区分析技术对2008年7月捕获于长江安庆江段的10尾刀鲚(均为传统意义上的长颌鲚)进行了耳石微化学研究。结果表明:这些个体均具典型的溯河洄游习性。从耳石核心到边缘定量线分析结果表明,耳石的沉积过程中元素Sr/Ca比值波动显著,不仅有对应淡水生境的低值(3)阶段,还具有对应河口半咸水、海水生境的高值(3)阶段。这种现象亦得到了16色Sr元素面分布分析结果的印证。根据耳石淡水系数、Sr/Ca比值高低波动特征及Sr元素面分布图谱的差异性可以将这些刀鲚分为3种淡-海水生境转换生活史类型。这种现象明显地反映出长江安庆江段刀鲚的群体具有个体组成和洄游模式的多样性。     

水温对刀鲚幼鱼耗氧率、窒息点、血糖及肌肝糖元指标的影响

实验测定了不同水温条件下刀鲚(Coilia nasus)幼鱼的耗氧率和窒息点,并对耗氧率的昼夜变化规律以及水温对刀鲚幼鱼血糖及肌肝糖元指标的影响进行了研究,旨在为刀鲚运输、养殖生产中制定合理的放养密度和养殖工艺提供参考依据.结果表明:在试验水温(16℃～28C)条件下,刀鲚幼鱼的耗氧率随水温的升高而增大,耗氧率(R)与水温(T)的回归方程为R=0.988T2-32.36T+343.7,相关系数为0.96;刀鲚幼鱼的耗氧率具有昼夜节律性,耗氧高峰出现在7:00,低谷在21:00;刀鲚幼鱼的窒息点与水温显著相关,窒息点A(mg·L-1)与水温T(℃)的回归关系为A=0.9397T0.8001,R2=0.98.刀鲚幼鱼血清中血糖含量在水温16℃～24℃阶段保持相对稳定,血糖含量在17.24 ～ 19.79 mmol·L-1,肌肉和肝脏糖元含量均呈波浪式变动;但在水温24℃～28℃阶段,血糖含量随水温上升而显著升高,而肌肉和肝脏糖元含量均显著降低.     

Reconstructing habitat use of Coilia mystus and Coilia ectenes of the Yangtze River estuary, and of Coilia ectenes of Taihu Lake, based on otolith strontium and calcium

The habitat use and migratory patterns of Osbeck's grenadier anchovy Coilia mystus in the Yangtze estuary and the estuarine tapertail anchovy Coilia ectenes from the Yangtze estuary and Taihu Lake, China, were studied by examining the environmental signatures of strontium and calcium in their otoliths using electron probe microanalysis. The results indicated that Taihu C. ectenes utilizes only freshwater habitats, whereas the habitat use patterns of Yangtze C. ectenes and C. mystus were much more flexible, apparently varying among fresh, brackish and marine areas. The present study suggests that the spawning populations of Yangtze C. ectenes and C. mystus in the Yangtze estuary consist of individuals with different migration histories, and individuals of these two Yangtze Coilia species seem to use a variety of different habitats during the non-spawning seasons.     

Genetic and morphological variation of three freshwater lake populations of Coilia ectenes (Engraulidae)

Population structure of the important commercial fish, Coilia ectenes was investigated in samples from three freshwater lakes in the Eastern China using a multivariate approach of morphometries and mitochondrial DNA control region sequencing. A total of eighteen morphological distances of truss method and eight morphometric variables were taken from each fish. Multivariate analyses of the morphometric data revealed significant morphological differences among the three lake populations, especially for those samples from Taihu Lake. Discriminant functions were used to compare sites, and these permitted an 83% success rate in distinguishing fish from the three sites. However, no obviously geographical differentiation was found among those populations of C. ectenes based on the genetic data. In the AMOVA analysis, only 2.2% genetic variability came from different populations, and most of them were present within the sub-populations. Experience a recent population expansion and some movement of fish among those areas, quite possibly enough to bring about relative genetic homogeneity, but there is insufficient to prevent the three populations from differing phenotypically. The diversified environmental factors may be playing an important role in shaping morphological variations among those populations.     

Pattern of selective constraint in C. elegans and C. briggsae genomes.

Similarity between related genomes may carry information on selective constraint in each of them. We analysed patterns of similarity between several homologous regions of Caenorhabditis elegans and C. briggsae genomes. All homologous exons are quite similar. Alignments of introns and of intergenic sequences contain long gaps, segments where similarity is low and close to that between random sequences aligned using the same parameters, and segments of high similarity. Conservative estimates of the fractions of selectively constrained nucleotides are 72%, 17% and 18% for exons, introns and intergenic sequences, respectively. This implies that the total number of constrained nucleotides within non-coding sequences is comparable to that within coding sequences, so that at least one-third of nucleotides in C. elegans and C. briggsae genomes are under strong stabilizing selection.     

Stabilities of consecutive A.C, C.C, G.G, U.C, and U.U mismatches in RNA internal loops: Evidence for stable hydrogen-bonded U.U and C.C.+ pairs.

The stability and structure of RNA duplexes with consecutive A.C, C.A, C.C, G.G, U.C, C.U, and U.U mismatches were studied by UV melting, CD, and NMR. The results are compared to previous results for GA and AA internal loops [SantaLucia, J., Kierzek, R., & Turner, D. H. (1990) Biochemistry 29, 8813-8819; Peritz, A., Kierzek, R., & Turner, D.H. (1991) Biochemistry 30, 6428-6436)]. The observed order for stability increments of internal loop formation at pH 7 is AG = GA approximately UU greater than GG greater than or equal to CA greater than or equal to AA = CU = UC greater than or equal to CC greater than or equal to AC. The results suggest two classes for internal loops with consecutive mismatches: (1) loops that stabilize duplexes and have strong hydrogen bonding and (2) loops that destabilize duplexes and may not have strong hydrogen bonding. Surprisingly, rCGCUUGCG forms a very stable duplex at pH 7 in 1 M NaCl with a TM of 44.8 degrees C at 1 x 10(-4) M and a delta G degrees 37 of -7.2 kcal/mol. NOE studies of the imino protons indicate hydrogen bonding within the U.U mismatches in a wobble-type structure. Resonances corresponding to the hydrogen-bonded uridines are located at 11.3 and 10.4 ppm. At neutral pH, rCGCCCGCG is one of the least stable duplexes with a TM of 33.2 degrees C and delta G degrees 37 of -5.1 kcal/mol. Upon lowering the pH to 5.5, however, the TM increases by 12 degrees C, and delta G degrees 37 becomes more favorable by 2.5 kcal/mol. The pH dependence of rCGCCCGCG may be due to protonation of the internal loop C's, since no changes in thermodynamic parameters are observed for rCGCUUGCG between pH 7 and 5.5. Furthermore, two broad imino proton resonances are observed at 10.85 and 10.05 ppm for rCGCCCGCG at pH 5.3, but not at pH 6.5. This is also consistent with C.C+ base pairs forming at pH 5.5. rCGCCAGCG and rGGCACGCC have a small pH dependence, with TM increases of 5 and 3 degrees C, respectively, upon lowering the pH from 7 to 5.5. rCGCCUGCG and rCGCUCGCG also show little pH dependence, with TM increases of 0.8 and 1.4 degrees C, respectively, upon lowering the pH to 5.5.(ABSTRACT TRUNCATED AT 400 WORDS)