The onset of spawning in the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters and its implications for management

Abstract The spawning periodicity of silver pomfret, Pampus argenteus (Euphrasen), was investigated against a background of conflicting evidence on the onset of spawning in this species. Contrary to the existing view that silver pomfret in Kuwait waters begin to spawn in March–April, evidence is presented that indicates a delay in spawning until May. Only an insignificant level of spawning takes place in April which, from the management point of view, may be ignored. The species has a prolonged spawning period extending from May to August in females, although the males mature in April and ripe specimens are encountered in monthly samples until September. There are two spawning peaks, the first one in May and the second in August.     

High allozyme variation and genetic similarity of two populations of commercial penaeids, Penaeus brevirostris (Kingsley) and P. vannamei (Boone), from the Gulf of California

Genetic resources assessment is considered as the starting point for population management in both fisheries and aquaculture. In this study, we have obtained genetic variability measures of two commercial penaeid shrimp species, Penaeus brevirostris (Kingsley) and P. vannamei (Boone), from the Gulf of California by means of starch electrophoresis analysis of 16 enzymatic systems, plus total protein. Thirty-two loci were resolved, which revealed polymorphism values (P₉₅) of 15.63% in P. brevirostris and 25.00% in P. vannamei. Unbiased expected heterozygosity (H_e) was 0.076 and 0.105 respectively. These are high genetic variability figures, taking into account the previously low genetic variability, assessed by means of allozyme variation, reported in several penaeid species around the world. Nei’s genetic similarity between the two species is 0.891.     

Global population genetic structure of the sequential hermaphrodite,dusky grouper (Epinephelus marginatus)

1. The dusky grouper Epinephelus marginatus is a large epinephelid species that occurs in the eastern and south-western Atlantic and western Indian Oceans. Late maturity, protogynous hermaphroditism, site fidelity, and overfishing have all contributed to its demographic decline.
2. Connectivity and demography within a broad sampling of dusky grouper populations throughout its distribution were assessed. To do so, genetic variation at 11 polymorphic microsatellite loci and a partial sequence of the mitochondrial control region (mtCR) were evaluated.
3. Two major mtCR lineages with a sequence divergence of 1.6% were found. The magnitude of genetic differentiation for mtCR among north and south Atlantic and Indian Ocean populations was high, with Φ_ST = 0.528.
4. D_EST and results of discriminant analysis of principal component revealed significant microsatellite genetic differentiation between all collection areas. Significant pairwise D_EST showed moderate (0.084) to very great (0.603) differentiation. The effective population size was low for all localities, ranging between 25 (Azores Archipelago) and 311 (Rio Grande do Sul). The overall effective population size was estimated as 299 (confidence interval = 215–412), and there was no evidence of strong or recent bottleneck effects.
5. Local and regional genetic structuring among dusky grouper populations is the consequence of the species' site fidelity, distribution across multiple oceanographic boundaries, and probably also of sequential hermaphroditism that contributes to the intensity of random genetic drift.
6. The spatial pattern of genetic structuring of dusky groupers is such that fisheries management and conservation of population genetic integrity will have to be pursued at the local and regional scales.

     

东海常见鲳属鱼类的形态差异及系统进化关系探讨

应用多变量形态度量学方法研究了鲳属中常见鱼类银鲳、翎鲳和中国鲳的形态差异,同时对3种鲳鱼线粒体DNA 16S rRNA基因序列差异进行了分析,并根据3种鲳鱼的形态和分子数据对其系统进化关系进行了探讨.聚类分析表明,银鲳和翎鲳形态较为相似,而与中国鲳形态差异较大.判别分析表明,3种鲳鱼形态上存在着明显差异,利用4个形态参...     

Genetic analysis of Rutilus rutilus caspicus (Jakowlew 1870) populations in Iran by microsatellite markers

The Caspian roach (Rutilus rutilus caspicus) is regarded as one of the most important commercial species in the Caspian Sea. Despite the commercial and conservation importance of the species, information on genetic relationships and diversities at the molecular level in Rutilus rutilus caspicus is scarce. Six microsatellite loci were analysed to study the genetic variation in two major populations of Caspian roach in the Iranian waters of the Caspian Sea: the Anzali Wetland and Gorgan Bay. The F_st value between populations was 0.07, suggesting that the genetic differentiation was significant (P<0.01). Both the studied populations deviated from Hardy–Weinberg equilibrium proportions at a number of loci, mostly due to the deficiency of heterozygosities. The genetic distance between populations was 0.29, which indicates that the genetic difference among the studied populations is pronounced. The differences between both populations were not statistically significant (P>0.05), neither for average number of alleles per locus nor for observed heterozygosities. The data generated in this study provide useful information on the genetic variation and differentiation in populations of Caspian roach.     

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。     

RAPD fingerprinting of the eel-loaches Pangio filinaris and Pangio piperata: preliminary evaluation

Random amplified polymorphic DNA (RAPD) analysis was applied to two morphologically similar species of the increasingly popular ornamental eel‐loaches, Pangio filinaris and P. piperata, collected from Kemat River, Terengganu and Padang Sanai River, Kedah, West Malaysia. Forty primers were tested in a preliminary screening. Of these, five (OPA‐03, OPA‐09, OPA‐11, OPA‐13 and OPA‐18) were chosen for their ability to provide consistent amplification. RAPD analysis differentiated the two species, with each showing different RAPD patterns for each primer used. The five primers generated a total of 82 scorable loci with up to 83% and 60% polymorphism in P. piperata and P. filinaris respectively. The RAPD banding patterns of these two species ranged from 2 to 14 fragments, with a size range of 250–2000 bp. Genetic similarity within species ranged from 0.610 to 0.985 (mean 0.799±0.14) for P. piperata and from 0.824 to 0.934 (mean 0.885±0.04) for P. filinaris respectively. The interspecies genetic similarity ranged from 0.386 to 0.486 with an average value of 0.434±0.040. Our study revealed RAPDs as useful genetic markers for the taxonomic clarification and assessment of genetic variability of the eel‐loaches.     

Identification of microsatellite loci and examination of genetic structure for the endangered springsnails Juturnia kosteri and Pyrgulopsis roswellensis in the Chihuahuan Desert

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Genetic structuring among populations of the great egret,Ardea alba egretta,in major Brazilian wetlands

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利用CO Ⅰ和Cytb序列探讨东海区3种鲳属鱼类的种群遗传结构

通过对CO Ⅰ和Cytb序列的分析,研究了银鲳(Pampus argenteus)、灰鲳(P.cinereus)和翎鲳(P.punctatissimus)3种东海区重要鲳属鱼类群体的种群遗传结构.在62个鲳属鱼类样本中分别检出CO Ⅰ和Cytb单倍型21个和27个,发现变异位点125个和176个.东海区的3种鲳属鱼类种...     

Spontaneous hybridization in the laboratory and genetic markers for the identification of hybrids between two atherinid species, Odontesthes bonariensis (Valenciennes, 1835) and Patagonina hatcheri (Eigenmann, 1909)

This study reports the occurrence of spontaneous hybridization between Odontesthes bonariensis (Valenciennes, 1835) and Patagonina hatcheri (Eigenmann, 1909), two South American freshwater atherinids, while adults of both species were being held in a communal laboratory tank, and describes suitable genetic markers for distinction of both species and their hybrids. Combined allozyme and mitochondrial DNA restriction length polymorphism analyses of offspring from three spawnings in the communal tanks confirmed the presence of hybrids along with purebreds in each spawning. Hybrids of an O. bonariensis mother X a P. hatcheri father were produced along purebred O. bonariensis in one occasion, whereas hybrids of P. hatcheri mothers X O. bonariensis fathers were produced along purebred P. hatcheri in two occasions. Three enzyme systems (coded by loci LDH-B*, PGM*, and CK*) out of 15 (20 loci) screened allowed distinction of species and their hybrids, but the usefulness of LDH-B* for field work may be limited by intraspecific polymorphism. Eight restriction enzymes (Apa I, Bgl II, Eco RI, Eco RV, Eco T22I, Hinc II, Hind III, and Pvu II) among 11 produced diagnostic restriction fragments applicable for species (motherhood) distinction. The relevance of these findings for the management of natural genetic resources and the aquaculture of these two species is discussed.     

Genetic relationship between Litopenaeus setiferus (L.) and L. schmitti (Burkenroad) determined by using 16S mitochondrial sequences and enzymatic analysis

Genetic differentiation and variability data of two populations of two species of shrimp (Litopenaeus setiferus (L.) and L. schmitti (Burkenroad)) have been obtained by electrophoretic analysis and by analysis of 16S mitochondrial DNA. Using eight polymorphic enzymes, the genetic distance (GD) between the two species was 0.165. The GD between L. setiferus populations was 0.0057 and between L. schmitti populations it was 0.0034. The greatest differentiation was found within, rather than between, populations, although the differentiation value between Mexican and Cuban populations varied in accordance with the geographic distance and ecological characteristic of each. We found a high similarity between these two species with a bimodal distribution of the loci with respect to genetic identity. The homology percentages for gene 16S fragments were compared with those from six different shrimp species (L. vannamei, L. stylirostris, Farfantepenaeus notialis, Metapeneopsis lamellata) and Artemia salina. Ninety‐seven percent of identity was found by analysis of a 409 bp of 16S mitochondrial DNA. With these values a phylogenetic tree was made using parsimony criteria. The GDs obtained with this method confirm the classification proposed by Pérez‐Farfante & Kensley (1997) .     

Development of 25 Novel Microsatellite Loci and Genetic Variation Analysis in Breeding Populations of the Pearl Oyster,Pinctada fucata

In this study, we screened 103,050 gene sequences of Pinctada fucata and identified 1450 simple sequence repeats (SSRs) distributing in 1355 sequences, in which 97 have sufficient flanking sequences for primer design, and 25 novel microsatellite loci were stable and polymorphic with N_a which varied from 2 to 6. Six microsatellite loci were found in the open reading frame of their corresponding sequences. With the 25 SSR loci, five breeding populations and a wild population, a total of 240 individuals from wild population (W), three consecutive selected populations (G₁, G_2, and G₃), and two backcross populations (D_o, D_r) (40 individuals per population) were assayed. In these populations, we detected 108 alleles of 111 bp to 362 bp. Each population had mean H_o of 0.5718–0.7366 and mean H_e of 0.5830–0.6954. Except the F_st = 0.0697 (W vs. G₃), pairwise F_st values ranged from 0.0131 to 0.0473, the genetic identity coefficients varied from 0.8688 to 0.9663, and genetic distance ranged from 0.0343 to 0.1307, all of these suggested that the breeding populations had genetic differentiation but at a low level generally. Besides, all the genetic index values, backcross populations (D_o, D_r) were higher than corresponding G₃ values, indicating that backcross could make the offspring incline to the recurrent parents.     

Genetic diversity and structure of Northern Sheatfish (Silurus soldatovi) assessed by newly developed and cross‐species microsatellites

Twenty‐five polymorphic microsatellite markers, including 13 newly isolated markers and 12 existing cross‐species markers, were used to assess the genetic variation of 141 individuals from three cultured stocks of northern sheatfish, Silurus soldatovi, in China. Samples were collected from Heilongjiang (H), Tongerpu (T) and Liaoning (L). Allelic richness, expected and observed heterozygosity among 25 loci were calculated, and the mean A_e, H_o and H_e were estimated in three stocks. In low polymorphic locus HLJcf19 and HLJcf38, most individuals in all three stocks were homozygous and had only one same allele, while only few heterozygous individuals had the other allele in one certain stock. And all the three stocks showed excess of heterozygotes, because of significant negative F_IS values. Genetic distance, UPGMA dendrogram, as well as structure analysis, all indicated that Stock H and L were closer among three stocks. The results revealed that though all stocks had no reduction in recent time, their effective population size were significantly lower to the ideal value.     

Cross-species amplification of microsatellite markers for the brown sole in the family Pleuronectidae

Amplification of eight microsatellite loci previously developed and characterized in brown sole Pleuronectes herzensteini was attempted in 11 other flatfish species. Two loci, Phz6 and Phz12, were amplified in all the species examined. Cross-species amplification was successful in eight loci of Kareius bicoloratus and Pleuronectes yokohamae, but in only seven loci of Microstomus achne, Pleuronectes punctatissimus, and Pleuronectes schrenki. Three to five loci could be amplified in six other species. In the three species selected, K. bicoloratus, P. punctatissimus, and P. yokohamae, seven to eight cross-amplified loci exhibited polymorphisms comprising 1–22 alleles. Expected heterozygosity (He) ranged from 0.66 to 0.96 in K. bicoloratus, from 0.62 to 0.96 in P. punctatissimus, and from 0.43 to 0.91 in P. yokohamae. Observed heterozygosity (Ho) ranged from 0.65 to 1.00 in K. bicoloratus, from 0.55 to 0.95 in P. punctatissimus, and from 0.40 to 0.95 in P. yokohamae. The Phz2, Phz3, and Phz12 loci significantly deviated in certain or all three species from Hardy–Weinberg equilibrium. The mean values of homology to the flanking-region sequences of brown sole were 93.7% in K. bicoloratus, 91.2% in P. punctatissimus, and 93.9% in P. yokohamae. These results suggest that microsatellite markers for brown sole are applicable for genetic studies in flatfish species including at least these three species.     

Identification of quantitative trait loci for growth‐related traits in the swimming crab Portunus trituberculatus

The swimming crab (Portunus trituberculatus) is an economically important species in Asian aquaculture. Implementing growth‐related traits of P. trituberculatus into genetic breeding programmes is an ongoing effort. We used a previously published genetic linkage map of P. trituberculatus, containing 55 simple sequence repeat (SSR) markers and 172 amplified fragment length polymorphism (AFLP) techniques to map quantitative trait loci (QTL) for growth‐related traits in a single full sibling F₂ family. Ten growth‐related traits were measured for QTL mapping. Composite interval mapping identified 9 QTL on the female map and 16 on the male map. Individual QTL with additive effects explained 11–38% of the phenotypic variance for various traits using the female parent's map, and from 1% to 21% using the male parent's map. Two QTL explaining a large percentage of variation in body weight were detected on chromosome 17 on the female map, and on chromosome 16 on the male map, and contributed 38% and 18% of the phenotypic variance respectively. This is the first study to report the detection and positioning of major QTL affecting growth in a true crab species (Brachyura). The mapping of growth‐related QTL in this study raises the possibility of improving the growth of P. trituberculatus through marker‐assisted selection.     

冬夏两季五种经济鱼类组织脂肪酸含量及组成分析

为了解不同季节不同鱼类不同组织中的不同脂肪酸含量,科学地指导鱼类膳食消费,本实验研究了冬夏两季,采集自上海市场常见的5种经济鱼类:大黄鱼(海洋肉食性),银鲳(海洋杂食性),日本鳗鲡(淡水肉食性),莫桑比克罗非鱼(淡水杂食性),草鱼(淡水草食性),分别检测鱼背部肌肉、腹部肌肉、尾部肌肉、肝脏和腹腔脂肪组织的脂肪含量和脂肪酸绝对含量。结果显示,5种鱼肌肉脂肪酸谱存在显著差异,并与各自的生活环境及食性均有关系;在鱼的腹腔脂肪或肝脏中,饱和脂肪酸(SFAs)和单不饱和脂肪酸(MUFAs)含量较高,且与组织脂肪含量密切相关;而多不饱和脂肪酸(PUFAs)、n-3系多不饱和脂肪酸(n-3 PUFAs)和n-6系多不饱和脂肪酸(n-6 PUFAs)含量较低,且与组织脂肪含量关系不大;大黄鱼和银鲳各肌肉组织中的n-3 PUFAs、二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)含量以及n-3/n-6值高于莫桑比克罗非鱼和草鱼,并与组织脂肪含量呈正相关;冬季草鱼腹部肌肉、莫桑比克罗非鱼尾部肌肉以及日本鳗鲡和银鲳的肝脏中的n-3 PUFAs含量较夏季高。研究表明,脂肪酸组成与物种、食性、水域环境以及季节温度和组织部位均有关系。从补充n-3 PUFAs摄入的角度分析,日本鳗鲡、大黄鱼和银鲳营养价值高于莫桑比克罗非鱼和草鱼,冬季鱼类的营养价值高于夏季。     

High gene flow in two migratory Neotropical fish species,Salminus franciscanus and Brycon orthotaenia,and implications for conservation aquaculture

1. Two migratory and endangered freshwater fish species, Salminus franciscanus and Brycon orthotaenia, are endemic to one of the most important basins for hydropower capacity in South America. These two fish are target species of conservation aquaculture programmes along the São Francisco River system.
2. In order to implement effective strategies for the conservation of these species, microsatellite markers were developed and used to assess the genetic diversity and structure among wild groups. Fish were collected during the spawning season at four sampling sites, covering more than 1000 km.
3. Polymorphism loci were assessed, and a total of 133 and 107 alleles were found for S. franciscanus and B. orthotaenia, respectively. Despite the critical conservation status, B. orthotaenia showed high levels of genetic diversity, comparable with those of other closely related species.
4. Salminus franciscanus exhibited half of the genetic diversity of its sister species in terms of allelic diversity, indicating that this species will be more prone to genetic drift and inbreeding in conservation aquaculture programmes.
5. The results of an analysis of molecular variance for microsatellite markers in these species (F_ST = 0.007 for S. franciscanus and F_ST = 0.003 for B. orthotaenia) and the estimated recent migration rates (>40% among sampling sites) support panmixia in both species, despite the heterogeneities of the riverscape.
6. The results of this study and the microsatellites developed will play an important role in assisting agencies in making informed decisions on conservation aquaculture programmes.

     

Genetic characterization and gonad development of artificially produced interspecific hybrids of the abalones, Haliotis discus discus Reeve, Haliotis gigantea Gmelin and Haliotis madaka Habe

Hybridization among abalone species has been suggested as a possible means to increase their growth rates for aquaculture. As a first step to test the usefulness of the hybrids of Japanese abalone species (Haliotis discus discus, Haliotis gigantea and Haliotis madaka) for aquaculture, we characterized the genetic background and gonad development of hybrids that were produced by artificial insemination. The hybrid status of the resulting offspring was confirmed by assaying 14 allozymes and by RFLP analysis of the 16s rRNA and cytochrome oxidase I (COI) regions of mtDNA using 13 restriction enzymes. Histological examination of the gonads of the hybrids was conducted in comparison with those of the parental species. Cross‐breeding among the three species was conducted successfully in all combinations although with lower fertilization rates (means of 1.3–60.8%) than the parental species (34.3–90%). Crosses between H. discus discus and H. madaka had higher fertilization rates (22.4–60.8%) than those involving H. gigantea (1.3–19.9%). The hybrids were ascertained by the presence of both parental genotypes at the LDH‐A, ME‐A, MDH‐A and GPI loci. The maternal origin of the hybrid mtDNA was confirmed by digestion with DdeI, TaqI, HpaII of the COI region. No polymorphism was observed in the 16S rRNA region. The hybrids had gonadal development and maturity stages similar to the parental species up to fully mature oocytes and sperm. They spawned upon stimulation and produced viable offspring with high fertilization rates and successful development to the juvenile stage in back‐ and homologous hybrid crosses.     

Isolation and characterization of 16 polymorphic microsatellite markers from Nibea albiflora

Nibea albiflora is a commercially important fish species in China. Herein we report 16 novel polymorphic microsatellite markers in Nibea albiflora by using the 5′ anchored polymerase chain reaction (PCR) technique. The characteristics of these loci were estimated by using a sample of 30 individuals. A total of 79 alleles were detected with an average of 4.9 alleles per locus. The number of alleles per locus ranged from three to nine. The polymorphism information content (PIC) values for the 16 microsatellite loci ranged from 0.3131 to 0.7910. The observed and expected heterozygosity per locus ranged from 0.2333 to 1.000 and from 0.3452 to 0.8421, with an average of 0.7248 and 0.6592, respectively. Four loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction (P < 0.0031), and no significant linkage disequilibrium between pairs of loci was found. This study provides useful information for studies on genetic diversity and structure, construction of genetic linkage maps of N. albiflora, and effective management of this fish resource.