Development of neutralizing antibody responses in muskellunge, Esox masquinongy (Mitchill), experimentally exposed to viral haemorrhagic septicaemia virus (genotype IVb)

A complement‐dependent 50% plaque neutralization test was used to assess the neutralizing antibody response in sera of muskellunge, Esox masquinongy, experimentally infected with viral haemorrhagic septicaemia virus (VHSV, genotype IVb) by immersion. Groups of muskellunge were challenged with varying concentrations of VHSV: Group 1 with 10² plaque‐forming units (pfu) mL^?1, Group 2 with 4 × 10³ pfu mL^?1, Group 3 with 10⁵ pfu mL^?1 and Group 4 with 0 pfu mL^?1. The fish were held at a temperature of 11 ± 1 °C and were sampled over a 20‐week period. Neutralizing antibodies were not detected in sera of any of the negative control fish throughout the study. Low neutralizing titres were detected in Groups 1–3 by 6 days post‐infection (p.i.). Neutralizing titres of <80 were not detected again until 3, 4 and 7 weeks p.i. for Groups 2, 3 and 1, respectively, with peak titres for those groups occurring 16, 11 and 17 weeks p.i., respectively. VHSV was detected in serum for up to 11 weeks p.i. Results of this study show that survivors can be detected by a serological technique, despite being virus negative. This may benefit the investigation of VHSV IVb distribution in the Great Lakes and the study of host immune responses to this emerging sublineage.     

Movement,home range and habitat selection of stocked juvenile muskellunge,Esox masquinongy,in Forbes Lake,Illinois: exploring the effects of latitudinal origin

Abstract Intraspecific, seasonal and diel variation in movement behaviours of three stocks of juvenile (age‐2; 399–610 mm total length) muskellunge, Esox masquinongy Mitchill, were assessed using radio telemetry in Forbes Lake (225 ha), IL, USA. Experimental populations included muskellunge from the Upper Mississippi (Leech Lake, MN, USA) and Ohio (Cave Run Lake, KY, USA) river drainages, as well as progeny from North Spring Lake, IL, a mixed‐origin stock. No differences in hourly movement rates or home ranges were detected among stocks. Movement rates were greatest during spring (mean ± SE = 42 ± 4 m h^?1), lowest during summer (16 ± 3 m h^?1) and intermediate in autumn (28 ± 5 m h^?1). Additionally, movement rates during the summer were greater at night than crepuscular periods. Home range sizes were similar during spring and autumn (mean ± SE = 17–18 ± 3–4 ha) and decreased during summer (5 ± 3 ha). Although habitat selection characteristics were generally similar among stocks, fish from the Upper Mississippi River drainage occupied deeper water more frequently and selected the pelagic zone more strongly during the spring than those from the Ohio River and mixed‐origin stocks. Within the littoral zone, muskellunge selected coarse woody habitat and aquatic macrophytes. Collectively, these findings suggest little behavioural differentiation among genetically divergent stocks when evaluated in a common reservoir environment.     

微卫星评价栉孔扇贝雌核发育二倍体纯合性

采用筛选获得的5对多态性微卫星引物对栉孔扇贝（Chlamys farreri）减数分裂雌核发育家系A和家系B、有丝分裂雌核发育家系A和家系B各30个个体、双亲及对照组40个个体进行了遗传变异分析,并对减数分裂和有丝分裂雌核发育后代的纯合性进行了比较。电泳结果表明,5对微卫星引物在减数分裂雌核发育和有丝分裂雌核发育个体中均能稳定重复地扩增出相应的序列;各雌核发育家系中均有部分个体出现父本基因,表明精子遗传物质失活不彻底,雌核发育组中存在正常受精个体;有丝分裂雌核发育二倍体在所有检测位点全部纯合,减数分裂雌核发育二倍体在部分位点纯合,但未发现在所有位点全部纯合的个体,在CFMSP007、CFMSP075、CFMSM009、CFMSM014和CFMSM020位点,杂合子比例分别为0．3400、0．3611、0．4884、0．4750和0．7500,平均杂合子比例为0．4829。研究结果显示,栉孔扇贝有丝分裂雌核发育二倍体均为纯合子,如精子的灭活率达到100％,有丝分裂雌核发育二倍体一代即可实现纯合,如再进行一次减数雌核发育即可建立纯系;减数分裂雌核发育二倍体由于具有较高的重组率,其与母本的遗传同质性较高。     

中国和匈牙利白斑狗鱼群体遗传变异的微卫星标记分析

本研究应用18个微卫星分子标记,对白斑狗鱼(Esox lucius L.)3个中国新疆群体(乌伦古湖、吉力湖和6号湖)和1个匈牙利巴拉顿湖群体的遗传结构进行了分析.结果表明,3个中国白斑狗鱼群体的平均等位基因丰富度(AR)、平均观测杂合度(Ho)和平均期望杂合度(HE)均显著低于匈牙利巴拉顿湖群体(P＜0.05),而匈牙利群体的平均近交系数(FIS)高于中国群体;经SMM和TPM模型检测,匈牙利白斑狗鱼群体存在显著的遗传瓶颈信号(P＜0.001);AMOVA和群体两两比较的FST值表明,中国与匈牙利白斑狗鱼的遗传分化十分显著(P＜0.01);NJ树、主成分分析(PCA)进一步证实中国白斑狗鱼与匈牙利白斑狗鱼群体间存在显著的遗传差异和分化.此外,贝叶斯遗传聚类结果表明,中国新疆6号湖白斑狗鱼群体极可能来源于乌伦古湖,而非吉力湖.     

Sectioned pelvic fin ray ageing of muskellunge Esox masquinongy from a Virginia river: comparisons among readers, with cleithrum estimates, and with tag–recapture growth data

Abstract  The potential utility of pelvic fin rays as ageing structures was evaluated for southern US muskellunge Esox masquinongy Mitchill populations by comparing age estimates among three readers and against cleithrum estimates, and by comparing observed length changes of tagged fish with changes predicted from growth equations based on pelvic fin ray age estimates. Mean coefficient of variation in age estimates among all readers and between the two readers with prior ageing experience was 17.8% and 5.6%, respectively. Exact and within 1-year agreement rates between pelvic fin rays and cleithra were 76% and 100%, respectively. Mean (± 2 SE) estimated absolute error between observed and predicted length changes for 13 tagged muskellunge was 30 ± 14 mm. This evaluation indicated that pelvic fin rays may prove to be a useful, non-lethal method for ageing muskellunge in southern US waters. Validation studies are still needed to ensure that growth rings form consistently throughout fish's life span.     

团头鲂耐低氧新品系雌核发育群体遗传结构的微卫星分析

为了指导团头鲂耐低氧群体的后续选育工作开展,利用筛选出的20对微卫星引物,比较分析了团头鲂耐低氧群体(TN)及其减数分裂(TNM)、有丝分裂(TNDH)雌核发育后代群体的遗传结构;结果显示,团头鲂TN、TNM、TNDH及团头鲂"浦江1号"(TPJ1)对照的平均等位基因数(N_a)分别为3.90、3.55、3.45、4.25,平均观测杂合度(H_o)分别为0.7853、0.3934、0.2768、0.8075,平均期望杂合度(H_e)分别为0.6491、0.5563、0.4870、0.6855,平均多态信息含量(PIC)分别为0.5695、0.4796、0.4181、0.6105,TPJ1对照群体的遗传多样性最高,TN群体较TPJ1群体的遗传多样性有所降低,但不存在显著差异,仍保持了较高的遗传杂合度,而2个雌核发育群体(TNM和TNDH)的遗传多样性显著低于TPJ1和TN群体,TNDH群体的遗传多样性显著低于TNM群体。Hardy-Weinberg平衡遗传偏离指数也表明团头鲂TPJ1和TN群体出现杂合子过剩现象,而TNM、TNDH雌核发育群体则出现了杂合子缺失现象,纯合子比例高。聚类分析表明,TPJ1和TN群体聚类成一个分支,而TNM、TNDH雌核发育群体聚类成另一分支,产生了一定程度的遗传分化。在TN群体中实施雌核发育可加速遗传物质的纯合,可用于团头鲂进一步耐低氧性状基因的纯化。     

草鱼野生与选育群体遗传变异微卫星分析

为探究经过2个选育世代后选育群体遗传多样性和遗传结构的变化,实验采用多重PCR技术对4个野生草鱼群体(邗江、九江、石首、吴江)和2个选育群体(F1和F2)进行了微卫星序列遗传变异分析。结果显示,6个草鱼群体遗传多样性水平较高,2个选育群体除了平均等位基因数外,其他遗传多样性参数均小于4个野生群体。哈迪—温伯格平衡(Hardy-Weinberg equilibrium)检测显示,在120个群体—位点组合中有62个位点显著偏离哈迪—温伯格平衡,62个群体—位点组合中只有11个组合其近交系数值为负值,其余的51个组合的Fis均为正值。6个草鱼群体AMOVA分析结果显示,3.75%的变异来自于群体间,96.25%的变异来自于群体内,整体的遗传分化指数值为0.038。进一步分析各个群体间Fst,只有石首群体与F1、F2群体之间的Fst大于0.05,处于中等分化,其余群体间分化程度较低,且F2群体与4个野生群体之间Fst比F1群体与4个野生群体之间的Fst大。奈氏标准遗传距离分析结果显示,2个选育群体与野生群体之间的遗传距离大于野生群体之间的遗传距离。基于Dn建立的UPGMA系统发育树得出了相同的结果,即2个选育群体与野生群体之间的亲缘关系比4个野生群体之间的亲缘关系要远。研究表明,经过2个世代选育后,相比4个野生群体,2个选育群体遗传多样性虽有部分下降,但仍处于较高的水平,2个选育群体的遗传结构已发生变化,但其遗传分化程度尚不明显。本研究结果为制定出更加完善有效的选育方案提供了重要参考。     

两个人工雌核发育系鲢近交F1遗传多样性的RAPD分析

采用RAPD技术对两个人工雌核发育系鲢近交F1遗传距离、遗传相似度及群体遗传多样性进行分析,用普通鲢和鲤作对照。结果表明：GSCⅠ、Ⅱ系近交F1系内个体间平均遗传相似度分别为0．9722、0．9807,高于对照鲢和鲤的0．9546、0．8727;两系近交F1的遗传多样性指数分别为0．0629、0．0529,低于对照鲢和鲤的0．1018和0．2132,表明GSCⅠ、Ⅱ系系内近交的F1保持了较高的纯度。LIPGMA和NJ系统树清晰反映了两个系近交F1与对照组个体问的相互关系。26个随机引物的RAPD扩增结果显示,5个引物OPG04、OPG17、OPP01、OPM11、OPM16可以扩增出区分两个系近交F1的特异标志带。     

Genetic relatedness and differentiation of hatchery populations of Asian seabass (Lates calcarifer) (Bloch, 1790) broodstock in Thailand inferred from microsatellite genetic markers

After more than 20 years of hatchery production of Asian seabass in Thailand, genetic information is still lacking for effective genetic management and a selective breeding programme. This study aimed to evaluate genetic status of existing hatchery populations and genetic consequences of a selective breeding attempt. We examined genetic relatedness in seven hatchery samples, including a selectively bred population (RACF‐F1), compared with three wild samples using 11 microsatellite loci. Genetic diversity and relatedness values within most hatchery samples, except for RACF‐F1, did not differ from those of wild populations (P > 0.05). RACF‐F1 had the lowest allelic diversity and effective population size (A_r = 6.99; N_e = 7.8) and highest relatedness values (mean r_xy = 0.075–0.204). Pairwise Φ_ST values, principal component analysis and model‐based cluster analyses revealed three genetically distinct hatchery groups: Eastern Thailand (CHN, RACF, NSCF and SKCF), Southern Thailand (NICA) and the Andaman Sea (STCF). Results suggest that exiting domestic populations capture reasonable amount of genetic variation and can be useful for a base population for genetic improvement programmes. In addition, given the rapid increase in relatedness that we observed in one selectively bred population, we recommend using selection methods and hatchery practices that reduce variability in family contribution in the subsequent generations.     

Genetic variability of cultured populations of the Pacific abalone (Haliotis discus hannai Ino) in China based on microsatellites

The genetic diversity of cultured populations of the Pacific abalone (Haliotis discus hannai Ino) from northern China was analysed using seven microsatellite markers. The microsatellite loci were polymorphic for all the populations, with an average of 8.7 alleles per locus (range 8.0–9.4). The mean observed and expected heterozygosities were 0.547 (range 0.500–0.596) and 0.774 (range 0.754–0.787) respectively. The allelic diversity in terms of number of alleles per locus was considerably lower than that previously found in wild populations (range 21.8–23.0), indicating that bottleneck effects occurred when each population was founded. Significant genetic differentiation among the five cultured populations was shown using F_st and R_st values, and pairwise comparison based on allelic distribution. A neighbour‐joining analysis of the genetic distance did not show a consistent relationship between the geographic and the genetic distances, suggesting the existence of exchanges of breeds and eggs between the hatcheries. The results obtained in this study are useful for a number of areas of interest for fisheries management and the aquaculture industry, especially with regard to breeding programmes.     

Loss of genetic variability in the captive stocks of tambaqui,Colossoma macropomum (Cuvier, 1818), at breeding centres in Brazil,and their divergence from wild populations

The loss of variability in farmed populations and the risks of interactions with wild populations support the need for the genetic monitoring of species farmed throughout the world. In Brazil, the tambaqui is the most widely farmed native fish species. Despite this, there are no data on the pedigree of the farmed stocks, and the potential for interactions with wild populations in the Amazon basin has raised concerns with regard to the genetic variability of these stocks. The present study analysed sequences of the mitochondrial Control Region and 12 microsatellites to characterize the genetic variability of seven historically important commercial tambaqui breeding centres located in four different regions of Brazil, and compared these sequences with those obtained from individuals collected from a wild population. High levels of genetic diversity were found in the wild population, whereas genetic diversity was reduced in both markers in most captive populations, except for the broodstock located near the Amazon River. High F_ST and D_EST indices were recorded between the wild population and most of the captive stocks analysed. The drastic reduction in genetic diversity found in most captive stocks and the difference between these stocks and the wild population may have been the result of the small size of the founding populations and the absence of breeding management. The renewal of the broodstocks and the application of breeding management techniques are recommended. In the Amazon region, in addition, the use of broodstocks that are genetically very different from local wild populations should be avoided.     

Induction of gynogenesis in stellate sturgeon (Acipenser stellatus Pallas, 1771) and its verification using microsatellite markers

Normal egg fertilization was carried out in stellate sturgeon Acipenser stellatus sperm by 60‐, 90‐ and 120‐s ultraviolet irradiation, and a cold shock was carried out afterwards. The treatments included haploids, diploid gynogens, triploid and control groups. Fertilization, hatching and survival rate at the 60‐s irradiation time were significantly greater than those in the 90‐s and 120‐s irradiation and control groups. Two pairs of microsatellite markers were used to find gynogenesis in comparison with the parental and offspring genome in one locus. The results showed all maternal genomes among gynogen offspring with no paternal genome. The markers also showed the maximum gynogenesis induction in the Gy60 treatment.     

Genetic changes during mass selection for growth in Nile tilapia, Oreochromis niloticus (L.), assessed by microsatellites

Two control (C1 or first control generation, and C4 or fourth control generation) and three selected (S1 or first selected generation, S2 or second selected generation, S4 or fourth selected generation) stocks of Chitralada Nile tilapia were analysed for microsatellite variation to determine the effect of size‐specific mass selection on genetic variability. Genetic variation based on five microsatellite loci (UNH123, UNH147, UNH172, UNH222 and UNH216) showed a slightly higher allelic diversity in the selected stocks (7.4–10 alleles) than in the control stocks (6.8–8.8 alleles). Apparent reductions in the mean number of alleles and H_e values were noted in successive generations of both control and selected lines. Significant deviations from Hardy–Weinberg equilibrium because of an excess of homozygotes indicated inbreeding in all control and selected stocks. Although estimated inbreeding levels were not significantly different among selected and control lines based on Welch's t‐tests, the increase in the degree of inbreeding within the selected line was higher (107.9%) than the control line (64.2%) after four generations. The implications of these results on the management and conservation of genetic diversity in improved breeds are discussed, while the importance of monitoring and minimizing inbreeding are likewise emphasized.     

Genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus) revealed by DNA microsatellites

To assess the genetic diversity of Nile tilapia Oreochromis niloticus, a total of 250 fish from five Egyptian populations were genotyped using six microsatellite markers. Heterozygosity and Wright's F‐statistics (F_IS, F_ST, and F_IT) were calculated to determine the genetic variation within and between these populations. Observed heterozygosities were in the range of 0.4 (Burullus) to 0.96 (Qena), with F_IS values ranging from 0.082 to 0.282. The mean F_ST showed that approximately 96.5% of the genetic variation was within‐population and 3.5% was among populations. Standard genetic distances were used to classify the five populations into two major groups. The deeper lotic river Nile populations of Assuit and Cairo formed one group and the shallow less lotic Delta lakes populations of Manzalla and Burullus formed the second group, with the upstream Nile Qena population being an outgroup. The findings from the current study help understanding of the broad‐scale population structuring of the Nile tilapia (O. niloticus) allowing the population groupings identified to act as potential sources of genetic variation. These populations could be included in future Marker‐Assisted‐Selection programs for economically desired production traits.     

福建漳浦太平洋牡蛎微卫星等位基因比较

本文采用Ucdcg153、157、202微卫星分子标记对福建漳浦从广东饶平引人的太平洋牡蛎育苗亲贝进行等位基因比较.两组样品(Cg♀和cg♂)携带的等位基因在微卫星重复区间及其附近存在高度相似的变异特征.这些特征区间分别是:Ucdcg153 23～40位碱基区间,Ucdcg157 73～100位碱基区间,Ucd-cg2...     

Genetic relationship between broodstocks of olive flounder, Paralichthys olivaceus (Temminck and Schlegel) using microsatellite markers

For the first generation of a selective breeding programme, it is important to minimize the possibility of inbreeding. This mostly occurs by mating between closely related individuals, while proper mating can provide an opportunity to establish the base families with wide genetic variation from which selection for subsequent generations can be more effective. Genotyping with microsatellite‐based DNA markers can help us determine the genetic distances between the base populations. The genetic markers further facilitate the identification of the correct parents of the offspring (parentage assignments) reared together with many other families after hatching. We established a genetic analysis system with microsatellite DNA markers and analysed the genetic distances of three farmed stocks and a group of fish collected from wild populations using eight microsatellite markers. The averaged heterozygosity of the farming stocks was 0.826 and that of the wild population was 0.868. The hatchery strains had an average of 8.6 alleles per marker, which was less than a wild population that carried an average of 14.3 alleles per marker. Significant Hardy–Weinberg disequilibrium (HWDE) was observed in two farming stocks (P<0.05). Despite relatively low inbreeding coefficiency of the hatchery populations, the frequency of a few alleles was highly represented over others. It suggests that the hatchery stocks to some extent have experienced inbreeding or they originated from closely related individuals. We will develop a selective program using the DNA markers and will widen the usage of the DNA‐based genetic analysis system to other fish species.     

Application of amplified fragment length polymorphism markers to assess molecular polymorphisms in gynogenetic haploid embryos of turbot (Scophthalmus maximus)

Among the variety of cultured marine species, the turbot Scophthalmus maximus is a fish of growing importance in European aquaculture. In this paper, an advanced application of AFLPs to estimate the genetic diversity of haploid gynogenetic families with the aim of obtaining a preliminary genetic map is presented. Ten EcoRI/TaqI primer combinations were tested in four families comprising diploid mothers and their haploid progenies. The amplified fragment length polymorphism (AFLP) analysis revealed an average of 6.8 polymorphic bands per primer combination and a total number of 88 polymorphisms out of 579 fragments. Among various primer pairs, seven combinations were selected in relation to the quality of profiles and number of polymorphic fragments, to be used in the determination of genetic linkage relationship between AFLP markers within the largest haploid family. Co‐migration of non‐homologous fragments was also investigated in one primer combination adding a fourth selective nucleotide to the three used in the classic TaqI AFLP protocol. Surprisingly, a rate of 38.7% of non‐homologous fragments co‐migrating with monomorphic bands was identified, due to the combined effect of homoplasy and the protocol used. Additional polymorphic markers discovered by this protocol were included in the linkage map. The turbot AFLP linkage map comprises 52 AFLP markers distributed in 12 linkage groups. On the basis of this map, turbot expected total genome length sums up to 1225.6 cM. The results confirm the usefulness of AFLPs in revealing genome segregation in haploid turbot progeny.