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Half-smooth tongue sole (Cynoglossus semilaevis) is one of the most important flatfish species for aquaculture in China. To produce a monosex population, we attempted to develop a marker-assisted sex control technique in this sexually size dimorphic fish. In this study, we identified a co-dominant sex-linked marker (i.e., CyseSLM) by screening genomic microsatellites and further developed a novel molecular method for sex identification in the tongue sole. CyseSLM has a sequence similarity of 73%–75% with stickleback, medaka, Fugu and Tetraodon. At this locus, two alleles (i.e., A244 and A234) were amplified from 119 tongue sole individuals with primer pairs CyseSLM-F1 and CyseSLM-R. Allele A244 was present in all individuals, while allele A234 (female-associated allele, FAA) was mostly present in females with exceptions in four male individuals. Compared with the sequence of A244, A234 has a 10-bp deletion and 28 SNPs. A specific primer (CyseSLM-F2) was then designed based on the A234 sequence, which amplified a 204 bp fragment in all females and four males with primer CyseSLM-R. A time-efficient multiplex PCR program was developed using primers CyseSLM-F2, CyseSLM-R and the newly designed primer CyseSLM-F3. The multiplex PCR products with co-dominant pattern could be detected by agarose gel electrophoresis, which accurately identified the genetic sex of the tongue sole. Therefore, we have developed a rapid and reliable method for sex identification in tongue sole with a newly identified sex-linked microsatellite marker.

The half-smooth tongue sole (Cynoglossus semilaevis) is an important cultured marine fish as well as a promising model fish for the study of sex determination mechanisms. In the present study, a protocol for artificial induction of mitogynogenesis by hydrostatic pressure using heterologous sperm was developed in half-smooth tongue sole in order to assess homozygosity of gynogens and to identify WW super-female. The optimal initiation time for pressure shock of mitogynogenetic embryos was determined to be 21.5 min after insemination when water temperature is at 22-23°C, while the optimal pressure and treatment duration were determined to be 70 MPa for 4 min. About 1,500 mitogynogenetic diploid larvae were obtained. Ten tongue sole microsatellite markers were used for homozygosity analysis of 24 mitogynogenetic larvae. Among the 24 larvae, the percentage of homozygosity ranged from 73.91% to 87.50% with an average homozygosity of 80.54%. Sex-specific simple sequence repeat (SSR) markers, CseF-SSR1, were isolated and used for identifying WW super-female mitogynogens in the tongue sole. The amplification of genomic DNA using the sex-specific SSR marker produced one DNA band of 206 bp in ZZ males, two DNA bands of 206 and 218 bp in ZW females, and one DNA band of 218 bp in WW super-females. Four WW "super-female" gynogens were observed in 39 mitogynogenetic diploids, indicating a ZW sex determination mechanism in the tongue sole. Thus, a protocol for the induction of artificial mitogynogenesis has been developed for the first time in half-smooth tongue sole, and the WW super-female diploids were identified in the mitogynogens by sex-specific SSR markers. These findings lay the foundation and provide important tool for the elaboration of sex determination mechanism, generation of WW super-females, and development of clone line and breeding of all-female stock in the half-smooth tongue sole.

The first set of 18 polymorphic microsatellite markers were developed from bluefin leatherjacket (Navodon septentrionalis Gunther, 1877). From a (GT)n-enriched genomic library, we got 121 microsatellites, of which 60 were randomly selected for designing microsatellite primers. Eighteen of these loci were polymorphic in a test population of 32 individuals with alleles ranging from 2 to 9, and expected and observed heterozygosities from 0.1463 to 0.8517 and from 0.1562 to 1.0000, respectively. No significant linkage disequilibrium between pairs of loci was found, but three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate population structure in bluefin leatherjacket.

In the present study, 10 polymorphic microsatellite DNA loci from Atlantic halibut (Hippoglossus hippoglossus) were isolated and characterized. The number of alleles for these loci ranged from 2 to 4 in tested 24 individuals. Observed and expected heterozygosities per locus varied from 0.21 to 0.70 and from 0.31 to 0.65, respectively. Most of these 10 microsatellite loci were successfully amplified and showed polymorphic in five related species. These loci will be useful for the assessment of genetic diversity and population structure of Atlantic halibut.

A microsatellite-enriched genomic DNA library of Navodon septentrionalis was generated and screened by sequencing. Ten dinucleotide microsatellite loci were characterized by genotyping 24 samples. The observed number of alleles ranged from two to seven with an average of 4.40, while the effective number of alleles ranged from 1.49 to 5.70 with an average of 3.31. The observed and expected heterozygosities ranged from 0.2917 to 0.9167 and from 0.3369 to 0.8422, respectively. No significant linkage disequilibrium between pairs of loci was found, but one loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci would be useful for investigating genetic population structure and molecule-assisted breeding for N. septentrionalis.

However,no reports are available on genetic diversity usingdifferent molecular marker techniques in China.Generally, the genetic diversity of introducedspecies will be reduced vastly due to the smaller ofeffective parent. In order to maintain sustaineddevelopment of the sole’s aquaculture in China,it is necessary to screen out molecular markersto analyze the genetic diversity in Senegal sole.MicrosatelliteDNAmarkershavebeenshowntobehighly polymorphic and useful as molecularmarkers for understanding population structure.

Small yellow croaker (Pseudosciaena polyactis) is an economically important marine fish species. About 43 microsatellite loci were isolated from two enriched genomic library of Pseudosciaena polyactis. Ten of these loci were polymorphic in a test population with alleles per locus ranging from two to six, and observed and expected heterozygosities per locus from 0.3750 to 0.8750 and from 0.3112 to 0.8121, respectively. No loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction and no significant linkage disequilibrium was found between pairs of loci. These polymorphic microsatellite loci would be useful for investigating genetic diversity of Pseudosciaena polyactis.

In the study, 34 microsatellite loci were isolated from a dinucleotide-enriched genomic library of Japanese Spanish mackerel (Scomberomorus niphonius). And 12 microsatellite loci were found to be polymorphic between 3 and 8 alleles. The number of observed and expected heterozygosity per locus in 23 individuals ranged from 0.6087 to 1.0000 and 0.8908 to 0.9773, respectively. Two loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction analysis and there was no significant linkage disequilibrium found between pairs of loci. As a result, 12 microsatellite loci probably located on different chromosome pairs and these polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in S. niphonius.

We describe the first isolation of 12 polymorphic microsatellite markers from Belenger’s jewfish (Johnius belengnerii Cuvier 1830). From a (GT)n-enriched genomic library, 54 microsatellites were selected for designing microsatellite primers, of which 36 gave working primer pairs. 12 of these loci were polymorphic in a test population of 21 individuals with alleles ranging from 3 to 18, and expected and observed heterozygosities from 0.5772 to 0.9449 and from 0.4286 to 0.9231, respectively. No significant linkage disequilibrium between pairs of loci was found, however, loci Jobe24 significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate population structure in Belenger’s jewfish.

Given the ecological and commercial importance of the summer flounder (Paralichthys dentatus), there is a surprising paucity of information on the molecular genetics of this species. Some studies published to date are concentrated on the reproduction biology. To address this shortcoming, a microsatellite-enriched genomic DNA library of P. dentatus was generated and screened by sequencing. Twelve dinucleotide microsatellite loci were characterized by genotyping 24 samples. The observed number of alleles ranged from three to thirteen with an average of 8.25, while the effective number of alleles ranged from 2.21 to 8.28 with an average of 5.06. The observed and expected heterozygosities ranged from 0.0833 to 0.9583 and from 0.5594 to 0.8980, respectively. Significant deviations from Hardy–Weinberg expectations were detected at three loci and linkage disequilibrium between two loci was significant after applying Bonferroni correction. In cross-species amplification, three species showed at least two polymorphic loci. The 12 highly polymorphic microsatellite markers represent a powerful molecular tool, which will allow for detailed population genetic analyses on this important marine fish.

The first set of polymorphic microsatellite markers were developed from so-iuy mullet (Mugil soiuy Basilewsky 1855). From a (GT)n-enriched genomic library, 53 microsatellites were selected for designing microsatellite primers, of which 36 gave working primer pairs. Ten of these loci were polymorphic in a test population of 24 individuals with alleles ranging from 3 to 9, and observed and expected heterozygosities from 0.2083 to 0.9167 and from 0.2651 to 0.8812, respectively. No significant linkage disequilibrium between pairs of loci was found, but two loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in Mullet.

Chinese sea perch (Lateolabrax maculates) is one of the most important commercial species of mariculture in China. In this study, we constructed a repeat-enriched genomic DNA library of L. maculates. Eighteen dinucleotide microsatellite markers were characterized by genotyping 32 samples. The number of alleles ranged from three to nine, and the observed and expected heterozygosities ranged from 0.4516 to 1.0000 and from 0.4045 to 0.8676, respectively. Significant deviations from Hardy–Weinberg expectations were detected at four loci and linkage disequilibrium between two loci was significant after applying Bonferroni correction. The 18 highly polymorphic microsatellite markers should provide sufficient level of genetic diversity to investigate the population structure and evaluate the breeding strategy in L. maculates.

The half-smooth tongue sole (Cynoglossus semilaevis, hereafter, “tongue sole”) is a marine flatfish with great commercial importance for fisheries and aquaculture in China. It has also been a promising model for the study of sex determination mechanisms in fish. Here, we report the construction of a genetic linkage map for the tongue sole, based on 137 markers including 103 AFLP markers, 33 microsatellite markers, and one female-specific DNA marker. Twenty-six linkage groups (LGs) were found. The total map length was 934.6 cM (Kosambi), with an average spacing of 8.4 cM, covering 64.4% of the estimated genome size. Furthermore, a female-specific SCAR marker, CseF-382, was mapped on LG5. This study represents the first genetic linkage map in the tongue sole. This map has great potential in the identification of quantitative traits loci and sex-related genes and marker-assisted selection in the tongue sole. Meanwhile, the new set of polymorphic microsatellite markers developed in this study is not only useful for genetic mapping but also of critical importance for studies on genetic diversity and broodstock management in tongue sole.