锦江翘嘴鲌的繁殖生物学特征

对2015年1月至12月采集于锦江的翘嘴鲌(Culter alburnus)进行了繁殖生物学特征的研究。锦江的翘嘴鲌繁殖期集中在6~7月,属分批产卵类型。繁殖群体年龄在3+龄至6+龄之间,体长250~537 mm,体重184.9~2 587.5 g。雌雄性比1.14︰1,体表差异表现在泄殖孔和腹部膨胀程度,雌雄群体间体长-体重关系存在显著性差异(0.01P0.05)。性成熟雌鱼绝对繁殖力25 067~54 274粒,相对繁殖力24.2~36.9粒/g,平均卵径(1.1±0.3)mm。性成熟系数在1~5月份逐渐增大,6月明显上升,7月达到最高峰,8月显著下降,9~12月逐渐趋于平缓。采用Logistic方程推算了初次性成熟个体特征,雄性体长273 mm,体重192.0 g,年龄3.4龄;雌性体长311 mm,体重249.4 g,年龄4.2龄。锦江种群繁殖期与其他地理种群相近,但绝对繁殖力和相对繁殖力明显偏小。     

时过境迁：野鸭落在稻田里

自2000年秋天,薛瑞华家96亩收割后晾晒在地里的稻子,一夜之间遭受野鸭子祸害后,此后每年秋天野鸭子都会如期“光顾”。这组图片纪录的是2007年10月14日兴凯湖农场25队职工张国林等农户的稻田遭野鸭祸害后的残况．人们查看后估算,仅这一次就有60亩稻子被野鸭连吃带祸害,60％的稻穗散落在泥地里。人们瞅着没有稻粒的空穗子和散落在泥里的稻粒,显得很无奈。     

翘嘴鲌鱼种对磷的需求量

以磷酸二氢钠为磷源,制成含磷水平为0.53%—1.61%的7种半精制试验饲料,饲养7组三重复的翘嘴隔冬鱼种。试验鱼每尾平均体重3.79±0.20g。饲养期为8周。试验结果表明,饲料磷含量不足会导致鱼体生长不良,饲料效率低下。饲料磷为0.88%或以上时,鱼体增重和饲料效率显著提高。全鱼脂肪含量随饲料磷水平上升而呈下降趋势,但各试验组间无显著差异(p>0.05)。全鱼的粗灰分含量与饲料磷水平呈正相关。饲料磷水平为0.88%或更高时,全鱼磷含量和脊椎骨的灰分含量稳定在同一水平上。饲料磷水平对全鱼水分、全鱼粗蛋白、鳞片灰分、鳞片磷和脊椎骨磷含量无显著影响(p>0.05)。因此,满足翘嘴鱼种生长所需的饲料磷为0.88%。     

徐家河水库翘嘴鲌的个体生殖力

2008年4-6月,在徐家河水库采集性成熟翘嘴鲌雌鱼,取鳞片鉴定年龄(A),测量其体长(L)、体质量(M)和性腺质量(M_o)等形态指标,用称量法计数个体绝对生殖力(F),据此计算体长相对生殖力(F_L)、体质量相对生殖力(F_M)、成熟系数（GSI）和肥满度(CF)等指标,对徐家河水库翘嘴鲌个体生殖力与形态指标的关系进行了分析.结果表明：调查样本由2⁺～5⁺龄组成,个体绝对生殖力与体长、体质量和年龄分别呈幂函数、幂函数和直线相关,体长相对生殖力与体长、体质量和年龄也分别呈幂函数、幂函数和直线相关,而体质量相对生殖力与各形态指标的相关性不显著.多元逐步回归分析结果表明,研究区翘嘴鲌个体绝对生殖力与体质量和性腺质量密切相关,体长相对生殖力与性腺质量、肥满度和成熟系数密切相关,而体质量相对生殖力仅与成熟系数相关.     

多基因联合揭示海南鲌的遗传结构与遗传多样性

海南鲌(Culter recurviceps)是我国华南地区重要经济鱼类, 由于受到近些年水利开发、过度捕捞、环境污染等诸多因素的影响, 其资源量快速下降, 亟需得到更多的关注和保护。为保护和合理开发海南鲌种质资源, 本研究采集了华南地区23个地理群体207尾海南鲌样本, 测定了2个线粒体基因(Cytb和ND2)并从Barcode of Life Data System数据库获得相对应线粒体COI基因, 结合多种分析方法(系统发育分析、分化时间估算、单倍型网状图、群体遗传分析和Mantel检验)对海南鲌的遗传结构和遗传多样性展开研究。系统发育分析和单倍型网状图表明华南地区海南鲌群体被分成3个谱系(I、II和III), 其中谱系I和III由珠江的群体组成, 谱系II由海南岛的群体组成。分化时间估算发现3个谱系之间的分化时间介于0.028-0.251 Ma之间, 表明华南地区更新世气候变化可能是造成海南鲌谱系分化的重要原因。群体遗传分析发现海南鲌群体之间存在极显著的遗传分化(F_ST = 0.511, P < 0.001), 并且符合距离隔离模式(R = 0.348, P = 0.0010)。群体动态历史分析表明, 海南鲌群体可能在0.010-0.025 Ma经历了群体扩张, 表明更新世的气候波动也影响了海南鲌的群体大小和分布。综上所述, 海南鲌群体由3个谱系组成, 更新世气候变化是导致3个谱系分化和影响海南鲌群体动态历史的重要因素。此外, 海南鲌群体之间的遗传分化也可能受到了空间距离的影响。     

翘嘴红鲌苏州和宜兴养殖种群的遗传多样性分析

目的:对翘嘴红鲌养殖种群遗传多样性进行分析,以科学地评价它们的种群遗传结构。方法:采用RAPD技术,对翘嘴红鲌苏州和宜兴养殖种群的遗传多样性进行分析。结果:苏州养殖种群的多态位点比例为25%,种群平均杂合度为0.1654,Shannon多样性指数为0.671;宜兴群体的多态位点比例为22.4%,群体平均杂合度为0.1446,Shannon多样性指数为0.0594。苏州群体内各个体之间的遗传相似度度为0.9378,遗传距离为0.0622;宜兴群体内各个体之间的遗传相似度度为0.9444,遗传距离为0.0556;两群体之间的遗传距离为0.0146。结论:两种群具有较低的遗传多样性。     

Ontogenetic development,allometric growth patterns,and daily increment validation of larvae and juvenile Culter alburnus

Fish ontogeny, allometric growth patterns, and otolith microstructure are fundamental in aquaculture and essential for understanding the early-life ecology of fish. Culter alburnus is a commercially important fish species and an excellent breeding target for aquaculture. In this study, newly hatched C. alburnus larvae were reared to the juvenile stage in a hatchery. Three days post hatch, the eyes, mouth, and intestine had developed, and the larval yolk sac had been completely absorbed. Fin rays started to differentiate in the flexion stage and were fully developed by the postflexion stage. Pigmentations were well developed in the juveniles. Culter alburnus larvae were characterized by 39–43 myomeres and 23–25 anal fin rays, swim bladder shape, and pigmentation. Head length, height, and musculature height showed positive allometric growth patterns, suggesting that head and trunk growth was prioritized. Positive allometric growth of the tail was simultaneous with the formation of fins, suggesting that swimming mode transformation, diet changes, and habitat shifts occurred after the start of the postflexion stage. Otolith growth increments in both the sagittae and lapilli were deposited daily, with the first increment formed on day 1 on the sagittae and day 4 of yolk sac absorption on the lapilli. Increments were thin and faint during the early developmental stage, gradually increasing to reach the broadest widths and the strongest contrast at the postflexion stage, which may be related to habitat shifts. This information will assist in the breeding and hatchery production of C. alburnus and establish suitable methods for analyzing this species’ spatiotemporal distributions and early-life traits.

     

长湖达氏鲌的生长特性及其资源现状

2015年9月至2016年8月在湖北长湖采集达氏鲌(Culter dabryi)样本592尾,对其年龄、生长及资源状况进行了研究。结果表明,长湖达氏鲌种群的年龄组成为1~7龄,其中以1~4龄鱼为主,占样本总量的91.38%;达氏鲌属匀速生长类型,其体重(W)和体长(L)的关系式为W=0.008L3.148(n=592,R~2=0.995,P0.01),且无明显性别差异;采用von Bertalanffy生长方程分别拟合体长、体重与年龄的关系,其表达式分别为,体长Lt=49.103[1﹣e-0.194(t+0.268)],体重Wt=1668.330[1﹣e-0.194(t+0.268)]3.148,生长拐点年龄t=5.64龄,对应体长33.4 cm,体重502.4 g;目前长湖达氏鲌总死亡系数Z=0.80,自然死亡系数M=0.42,捕捞死亡系数F=0.38,资源开发率E=0.48/年,根据体长股分析法估算出长湖达氏鲌2015~2016年资源量为1 809 710尾(15.18 t)。为保持长湖达氏鲌资源稳定,建议捕捞体长33.4 cm以上个体。     

Characterization of microsatellites and repetitive flanking sequences (ReFS) from the topmouth culter (Culter alburnus Basilewsky)

The topmouth culter (Culter alburnus) is an economically important freshwater fish in China. We obtained 159 microsatellite containing sequences (MCSs) from genomic DNA in this species enriched by (CAA)₈ and (GAA) ₈ probes. Careful examination of these sequences revealed the existence of cryptic repeated elements on presumed unique flanking regions. These cryptic elements can be grouped into three families, with the MCSs of the each family sharing regions of similarity ranging between 40 and 130 bp in length, with 96% sequence similarity. Repbase scans revealed that a large proportion of the cryptic repetitive DNA was identified as transposable elements (TEs). Complex patterns were apparent among these sequences. In most (89.2%), a single TE was identified in an MCS, in three instances, the same TE was observed twice in the same MCS. Some MCS have two or even four different TEs. We isolated nine polymorphic microsatellite loci from sequences with no matches to TEs. In a sample of 30 cultured C. alburnus, we found that the average allele number was 8.1 per locus (range = 4–17), with polymorphism informative content ranging from 0.364 to 0.898. These microsatellites can be used to study the population genetic diversity of this species.     

Assessing the genetic diversity and population structure of Culter alburnus in China based on mitochondrial 16S rRNA and COI gene sequences

The genetic diversity and population genetic structure of Culter alburnus were investigated using mitochondrial cytochrome c oxidase subunit I (COI) and ribosomal 16S subunit (16S rRNA) gene sequences. A total of 89 individuals from four localities were included in the analysis. Overall, 12 polymorphic sites were observed and 10 haplotypes were defined. The C. alburnus populations were characterized by high haplotype diversity (0.587 ± 0.047) and low nucleotide diversity (0.00197 ± 0.00073). Pairwise fixation index (F_ST) analysis indicated significant genetic differentiation among different populations. The hierarchical analysis of molecular variance (AMOVA) analysis also showed significant genetic divergence (φ_ST = 0.3792, P < 0.01) among these populations. The present results suggest that subdivisions exist among four C. alburnus populations, and should be considered as different management unit for effective conservation and management purposes. This study provides new information for genetic assessment and will be crucial for establishing fisheries management and strategies for this species.     

Determination of genetic diversity of wild and cultured topmouth culter (Culter alburnus) inhabiting China using mitochondrial DNA and microsatellites

The topmouth culter (Culter alburnus) is one of the most commercially important freshwater fish species inhabiting China. However, very limited information is available regarding its genetic diversity and population structure, thus hindering the effective management of this fish stock. Understanding the genetic diversity of wild and cultured topmouth culter populations is highly relevant for successful hatchery management. This study evaluated the genetic diversity and structure of five wild and two cultured populations of topmouth culter in China by using microsatellites and mitochondrial DNA. The genetic diversity of wild populations was found to be lower than that of cultured populations. This finding indicates that wild topmouth culter resources should be protected to prevent further degeneration and extinction. Moreover, it demonstrated that cultured populations have greater breeding potential than wild ones. Subdivisions among wild populations were observed, which should be considered as different units for conservation and hatchery management.     

基于线粒体CO 1基因序列的DNA条形码在鲤科鲌属鱼类物种鉴定中的应用

本研究探讨了线粒体CO1基因作为DNA条形码对鲌属鱼类进行物种鉴定的可行性。研究中获得了鲌属4种鱼类共32个个体长度为816bp的CO1基因序列。利用MEGA软件计算鲌属鱼类种间及种内遗传距离,利用邻接法、最大简约法、最大似然法和Bayesian方法分别构建分子系统树。结果显示,鲌属鱼类的种间遗传距离显著大于种内遗传距离。在系统树中,鲌属鱼类每一物种的个体分别形成各自独立的分支。基于CO1基因的DNA条形码在识别鲌属鱼类物种方面和传统形态学基本一致,而且该基因可以探讨鲌属鱼类种间的系统发育关系。本研究表明以CO1基因作为鲌属鱼类DNA条形码进行物种鉴定具有一定的可行性。     

Comparative analysis of the complete mitochondrial genomes of three geographical topmouth culter (Culter alburnus) groups and implications for their phylogenetics

Topmouth culter (C. alburnus) is an important commercial fish in China. We compared the nucleotide variations in the mtDNA genomes among three geographical groups of Culter alburnus: Liangzi Lake, Hubei Province (referred to as LZH); Taihu Lake, Jiangsu Province (TH); and Poyang Lake, Jiangxi Province (PYH). The similarity of whole mtDNA genomes ranged from 0.992 to 0.999. The similarity among 13 protein-coding genes, 2 rRNA genes, and the D-loop sequences was found to range from 0.982 to 0.996. This is useful data for future designing work for making specific molecular marker for distinguishing individuals of C. alburnus from the three geographical groups. An extended termination-associated sequence (ETAS) and several conserved blocks (CSB-F, CSB-E, CSB-D, CSB1, CSB2, and CSB3) were identified in the mtDNA control regions. A phylogenetic analysis shows a monophyletic relationship of the LZF-female and the LZF-male. However, the analysis also showed paraphyletic relationships for the other two geological groups. This result will be useful for the future breeding work of C. alburnus.     

Fatty acid profiles of the topmouth culter (Culter alburnus Basilewsky, 1855) from five lakes located at different latitudes in China

The topmouth culter (Culter alburnus Basilewsky, 1855) is a freshwater carnivorous fish of high nutritional value and widely distributed in lakes and reservoirs of China. In order to evaluate the fatty acid profiles in relation to habitat characteristics and to elucidate the main composition predictors, C. alburnus were collected from five lakes (Xingkai‐ LXk, Hongze‐ LHz, Kuilei‐ LKl, Chidong‐ LCd and Dongting‐ LDt) in China, ranging in latitudes from 28°30′ to 44°44′N and altitudes from 4 to 64 m. Ten fish from each lake ranging in total lengths from 414.2 to 423.9 mm were sampled between May to June in 2013 and 2014. A total of 23 fatty acids were identified using gas chromatography. Fatty acids that predominated in muscle samples of the fish were 16:0, 18:0, 16:1n?7, 18:1n?9, 20:5n?3, 22:6n?3 and 20:4n?6. Important differences in the fatty acid profiles of fish from high and low latitude lakes were discernible in that the two high latitudinal lakes (LXk and LHz) had significantly higher (p < .05) ratios of n?3 to n?6 fatty acids and levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), than those fishes in the low latitudinal lakes (LKl, LCd and LDt); these observations were confirmed by a principal component analysis. Therefore, it appears that multivariate analysis enables to distinguish fish from different lakes based on their characteristic fatty acid signatures; this would make a contribution to fish product traceability. The percentages of total saturated fatty acids increased significantly with increasing ambient temperature, and lakes at lower latitudes had higher levels of 17:0, 18:0, 18:2n?6, 20:3n?6 and lower levels of 16:1n?7 and 18:1n?9. Theoretical information criteria showed that the percentage of total saturated fatty acids varied more with temperature than with latitude and that this temperature‐dependent variation is nonlinear. Variation partitioning shows that most of the geographical variations are not only due to the nonlinear effects of temperature but also to the independent effects of the lake features. By contrast, no significant variations in fish lengths were found.     

Chromosome-level genome assembly and whole-genome resequencing of topmouth culter (Culter alburnus) provide insights into the intraspecific variation of its semi-buoyant and adhesive eggs

Topmouth culter (Culter alburnus) is an ecologically and economically important species belonging to the subfamily Culterinae that is native to and widespread in East Asia. Intraspecific variation of semi-buoyant and adhesive eggs in topmouth culter provides an ideal opportunity to investigate the genetic mechanisms of spawning habits underlying the adaptive radiation of cyprinids in East Asia. In this study, we present a chromosome-level genome assembly of topmouth culter and re-sequenced 158 individuals from six locations in China covering three geographical groups and two egg type variations. The topmouth culter genome size was 1.05 Gb, with a contig N50 length of 17.8 Mb and anchored onto 24 chromosomes. Phylogenetic analysis showed that the divergence time of the Culterinae was coinciding with the time of initiation of the Asian monsoon intensification. Gene family evolutionary analysis indicated that the expanded gene families in topmouth culter were associated with dietary adaptation. Population-level genetic analysis indicated clear differentiation among the six populations, which were clustered into three distinct clusters, consistent with their geographical divergence. The historical effective population size of topmouth culter correlated with the Tibetan Plateau uplifting according to the demographic history reconstruction. A selective sweep analysis between adhesive and semi-buoyant egg populations revealed the genes associated with the hydration and adhesiveness of eggs, indicating divergent selection towards different hydrological environments. This study offers a high-resolution genetic resource for further studies on evolutionary adaptation, genetic breeding and conservation of topmouth culter, providing insights into the molecular mechanisms for egg type variation of East Asian cyprinids.     

Molecular characterization of trypsinogens and development of trypsinogen gene expression and tryptic activities in grass carp (Ctenopharyngodon idellus) and topmouth culter (Culter alburnus)

This study examined the gene structures and expression of trypsinogens, as well as the trypsin activities of the grass carp Ctenopharyngodon idellus (herbivorous) and the topmouth culter Culter alburnus (carnivorous), which are commercially important freshwater species of the family Cyprinidae in China. Isolated full-length trypsinogen cDNA clones were 869 bp and 857 bp. The deduced amino acid sequences were 242 aa and 247 aa long, both containing the highly conserved residues essential for serine protease catalytic and conformational maintenance. The results from isoelectric and phylogenetic analyses suggest that grass carp trypsinogen is grouped with teleost trypsinogen group I, while topmouth culter trypsinogen is grouped with group II. The expression pattern of trypsinogen mRNA was similar between these two species, appearing 2 days post-hatching (dph) and reaching peaks at 11 and 23 dph. The trypsin-specific activities in both species were detected 2 dph and reached the major peaks at 8 dph, however the minor peaks were observed at 20 dph in the grass carp and 17 dph in the topmouth culter. The trypsin-specific activity was significantly higher in the grass carp than in the topmouth culter, which may be attributed to the nature of their different nutritional habits.     

Effects of 17α‐methyltestosterone on the growth performance,development, and reproduction of gynogenetic topmouth culter (Culter alburnus Basilewsky)

This study investigated the effects of 17α‐methyltestosterone (17α‐MT) on the physiological properties of gynogenetic topmouth culter (Culter alburnus). Five 17α‐MT concentration (0, 10, 25, 40, and 60 μg/g) groups were set up in Experiment 1, and three treatment and recovery methods of the above five concentrations were studied in Experiment 2. In Experiment 3, fish were fed with increasing concentrations of 17α‐MT (from 40 μg/g to 140 μg/g) in an outdoor pond. In Experiment 1, growth was promoted during the initial 60 days in the 10 μg/g group, whereas inhibition was first observed at 20 days after treatment in the 60 μg/g group. Increased concentration (40–60 μg/g) of 17α‐MT significantly inhibited the expression of FOXL2 and CYP19a gene but significantly activated the expression of AMH and DMRT1 gene. The levels of superoxide dismutase, estradiol, testosterone, growth hormone, and tetraiodothyronine in the 40 and 60 μg/g groups were significantly higher than those in the other concentration groups at 40 days after treatment. In Experiment 2, almost all indexes detected besides the expression of reproduction‐related genes in the 17α‐MT treatment groups were recovered to those in the control groups. All gonads observed in Experiments 1 and 2 remained in a primordial state after treatment with different concentrations of 17α‐MT. In Experiment 3, 100% of the detected gonads developed into testes at 126 and 460 days post‐fertilization after three‐month outdoor 17α‐MT induction. These results suggest that 17α‐MT affects the physiological processes related to sexual differentiation in topmouth culter and that feeding 17α‐MT with increasing dose in an outdoor pond provides an effective protocol for producing neo‐male topmouth culter.