Comparative Analysis of Mitochondrial Control Region Sequence from Three Flatfish Species(Pleuronectidae)

The 5’-end of the mitochondrial control region sequences of three flatfishes (Pleuronectiformes: Pleuronectidae) were amplified and sequenced. These sequences were compared with those of other three Pleuronectids species retrieved from GenBank. A phylogenetic tree was constructed based on the partial control region sequences. The results of phyloge- netic analysis are consistent with those of conventional systematics. Compared to previous studies, the structure of the 5’-end of mitochondrial control region was analyzed. The terminal associated sequence motif and its complementary motif were i- dentified at the 5’-end of the sequences. A conserved sequence block, named as CM5’d, was identified in the 5’-end of con- trol region sequences in all Pleuronectids. Another central conserved sequence block, named as CSB-F, was detected in the central conserved blocks.

The Genetic Structure and Diversity of Repomucenus curvicornis Inhabiting Liaoning Coast Based on Mitochondrial COⅠ Gene and Control Region

[Object] This study was conducted to explore the genetic diversity and structure of the wild Repomucenus curvicornis inhabiting Liaoning Coast, China. [Method] The mitochondrial COⅠ gene and control region（CR） were PCR amplified from the wild R. curvicornis populations from the Liaodong Bay（n=22） and the northern Yellow Sea（n=18）, sequenced and analyzed for genetic diversity. [Result] The contents of A, T, C and G of 624 bp COⅠ gene were 24.09%, 31.04%, 25.28%, and 19.59%, and those of 460 bp CR fragment were 32.96%, 32.80%, 14.86% and 19.38%, respectively. The total number of variable sites, average number of nucleotide differences（ k）, haplotype diversity（H） and nucleotide diversity（π） based on COⅠ gene were 38, 4.67,（0.96±0.02） and（0.007 5±0.004 2）, and those based on CR fragment were 26, 3.35,（0.97 ±0.02） and（0.007 3±0.004 3）, respectively. Based on mitochondrial COⅠ gene and CR, the genetic diversity of Liaodong Bay population was lower than that of the northern Yellow Sea population. The AMOVA analysis based on CR fragments revealed almost significant genetic divergence between the Liaodong Bay and the northern Yellow Sea populations, while there was no significant genetic divergence based on COⅠ gene. The results showed that CR and COⅠ gene are effective molecular markers for detecting the genetic diversity of R. curvicornis population, while CR is more reliable than COⅠ gene in detecting the genetic structure. [Conclusion] CR is an appropriate marker for genetic analysis of marine fish population.

Genetic variation of the small yellow croaker(Larimichthys polyactis)inferred from mitochondrial DNA provides novel insight into the fluctuation of resources

The small yellow croaker(Larimichthys polyactis)belongs to the family Sciaenidae,which is an offshore warm fish species and widely distributed in the western Pacific.In this study,the variation of genetic diversity and genetic differentiation among L.polyactis populations was analyzed by mitochondrial DNA control region.A total of 110 polymorphic sites were checked,which defined 134 haplotypes.High level of haplotype diversity(h=0.993±0.002)was detected in the examined range.Population genetic structure analyse(analysis of molecular variance,Fst)showed there were high gene flow among L.polyactis populations.The result showed that there were relatively high genetic diversity and low genetic differentiation among the Yellow Sea and the East China Sea populations,which can be attributed to diverse habitats,wide distribution range and high mutation rate of control region.Using phylogenetic methods,coalescent analyses(neutrality tests,mismatch distribution analysis,Bayesian skyline analyses)and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidence,we inferred that the genetic make-up of extant populations of L.polyactis was shaped by Pleistocene environmental impacts on the historical demography of this species.Besides,relatively constant genetic diversity and larger effective population size were detected in recent L.polyactis population.The result showed that the fishing policy certainly,such as the summer closed fishing,played a role in protecting resources of L.polyactis.This study can offer a wealth of biological novelties which indicates genetic structure of L.polyactis population and provides the foundation for resources protection and policy setting.

Mitochondrial genotyping of cultured Piaractus brachypomus revealed low diversity and mutations in regions involved in metabolisms and proliferation

In Amazonia,small-oriented family businesses or communities cultivate freshwater organisms as a source of income.Although effective management is fundamental for optimizing cultivated stocks,Amazonian aquaculture belittles the importance of genetic diversity,relying primarily on phenotypical characteristics during breeders’selection.To provide a“proof of concept”built on the premise that implementing modern technologies is crucial to optimizing fish stocks in rural Amazonian fish farms,we conducted a pilot study assessing genetic diversity on cultivated Piaractus brachypomus from Caquet´a,Colombia.We used mitochondrial control region(CR)sequences to evaluate heterogeneity.Our data revealed low genetic diversity and suggested that most sampled individuals probably originated from a single maternal lineage.Haplotype diversification resulted from discrete point mutations not associated with geographical location.Polymorphisms accumulate in non-conserved CR regions,yet the most divergent haplotypes display mutations in conserved CR sequences with roles in mitochondrial metabolisms and proliferation.Overall,our results indicate a need in the local industry to design breeding strategies to enhance diversity to avoid deleterious effects caused by inbreeding and domestication.

Molecular markers for identifying a new selected variety of Pacific white shrimp Litopenaeus vannamei

Selective breeding of the Pacific white shrimp Litopenaeus vannamei during the last decade has produced new varieties exhibiting high growth rates and disease resistance.However,the identification of new varieties of shrimps from their phenotypic characters is difficult.This study introduces a new approach for identifying varieties of shrimps using molecular markers of microsatellites and mitochondrial control region sequences.The method was employed to identify a new selected variety,Kehai No.1(KH-1),from three representative stocks(control group):Zhengda;Tongwei;and a stock collected from Fujian Province,which is now cultured in China's Mainland.By pooled genotyping of KH-1 and the control group,five microsatellites showing differences between KH-1 and the control group were screened out.Individual genotyping data confirmed the results from pooled genotyping.The genotyping data for the five microsatellites were applied to the assignment analysis of the KH-1 group and the control group using the partial Bayesian assignment method in GENECLASS2.By sequencing the mitochondrial control regions of individuals from the KH-1 and control group,four haplotypes were observed in the KH-1 group,whereas14 haplotypes were obtained in the control group.By combining the microsatellite assignment analysis with mitochondrial control region analysis,the average accuracy of identification of individuals in the KH-1group and control group reached 89%.The five selected microsatellite loci and mitochondrial control region sequences were highly polymorphic and could be used to distinguish new selected varieties of L.vannamei from other populations cultured in China.

A preliminary investigation on genetic diversity of Sousa chinensis in the Pearl River Estuary and Xiamen of Chinese waters

In this study, the mitochondrial DNA （mtDNA） control region and the mitochondrial cytochrome b gene of stranded Indo-Pacific humpback dolphin （Sousa chinensis） samples from the Pearl River Estuary and Xiamen waters were sequenced and analyzed. The result of mtDNA control region revealed 34 variable sites and four unique haplotypes （named as A, B, C and D） identified among the total samples from these two water areas, and the most common haplotype （A） was shared by 75% of the dolphins sampled from the two water areas. The haplotypic diversity （h） was 0.455 and the nucleodde diversity （π） was 0.0088. The phylogenetic analysis showed that the haplotype A, C, and D were closely related, but the haplotype B （unique for XM01 from Xiamen） was far from the other three. By scanning cytochrome b fragments, two haplotypes （A and B） were identified in these two water areas, and the most common haplotype （A） was shared by 91.67% individuals, while XM01 from Xiamen as the only exception. The data suggest that there is a possibility of gene exchange between the two populations in the Pearl River Estuary and Xiamen waters, and there possibly exists a unique maternal lineage in Xiamen waters.

Genetic variation and population dispersal of Yangtze voles Microtus fortis calamorum in the Dongting Lake region

To understand genetic variation and population dispersal in the Yangtze vole Microtusfortis calamorum distributed in the Dongting Lake region, 144 individuals were collected from six habitat patches. The mitochondrial DNA control region was sequenced and 17 haplotypes were observed. Of the six investigated populations, haplotype and nucleotide diversities of those from larger patches were higher than those from smaller patches. Nonparametric correlation analysis showed that patch size had a positive correlation with haplotype diversity （r = 0.943, P 〈 0.01）. A neighbour-joining tree of the 17 haplotypes showed no geo- graphic genetic structure among the six populations. Analysis of isolation by distance showed that genetic differentiation among the six populations was not positively related to geographic distance. Analysis of mismatch distribution indicated that the voles had passed through a population expansion. The pattern of haplotype distribution in the Changsha population suggests that the population was established by a founder effect