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Freshwater prawns (Decapoda: Caridea: Macrobrachium) play an important role in domestic fishery resources. Culturing M. rosenbergii and M. nipponense brings great economic benefits, as the two species were widely farmed in China. M. qilianensis, a native species with natural distribution limited in Gansu province, was classified into genus Macrobrachium based on external morphological characters. In order to understand the molecular genetic differences among the three species of Macrobrachium, i.e., M. rosenbergii, M. nipponense, and M. qilianensis, we analyzed sequences of mitochondrial cytochrome oxidase subunit I (COI) of them. It would provide theoretical basis of exploiting and utilizing Macrobrachium resources rationally. A total of 30 individuals (10 individuals of each species) were collected from Gansu and Zhejiang province. Samples of M. qilianensis were wild, however, that of M. rosenbergii and M. nipponense were cultured. Their mitochondrial COI gene segment sequences were obtained by using the method of PCR amplification and sequencing. After alignment, 649 bp consensus sequences of COI were obtained. One hundred and sixty-nine variable sites were detected in all 30 individuals, accounting for 26.04% of total sequence. A total of seven haplotypes were also detected. Nucleotide diversity was 0.411% within M. rosenbergii, 0.092% within M. nipponense, and 0.031% within M. qilianensis. Genetic diversity of wild M. qilianensis was much lower than that of cultured M. rosenbergii and M. nipponense. Genetic distances between different haplotypes of the three prawns ranged from 19.87% to 23.84%. It suggested that the three species were valid species, because genetic distances among them were quite great. To further determine the taxonomic status of the three prawns in family Palaemonoidae, we downloaded the corresponding COI sequences of Palaemonoidae prawns from Genbank and analyzed the phylogenetic relationships of them. Phylogenetic tree (NJ)

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We used sequences of mitochondrial cytb and 16SrRNA gene segments in order to clarify the genetic diversity and population structure in three Chinese estuary populations of Coilia mystus: 21 individuals from ChangJiang River (Yangtze River) estuary, 22 from MinJiang River estuary, and 22 from ZhuJiang River (Pearl River) estuary (65 individuals total). We obtained 607 base pairs of consensus cytb sequence. Thirty four distinct haplotypes were detected among the 65 cytb sequences. The indexes of nucleotide diversity (π) in these three populations were ChangJiang 0.533%, MinJiang 1.135%, and ZhuJiang 0.268%. MinJiang is the largest of the three populations. Genetic distances within the populations were between 0.3 and 1.2%, and 0.8 to 10.8% among populations. The largest genetic distance was 10.8% between the ChangJiang and ZhuJiang populations, and the smallest was 0.8% between MinJiang and ZhuJiang populations. Analysis of molecular variance (AMOVA) analysis revealed that variation among populations accounts for 90.25% of total variation, suggesting that this is the main source of total variance. We obtained 470 base pairs of consensus sequence of 16SrRNA. We detected 19 distinct haplotypes among the 65 sequences. The indexes of nucleotide diversity (π) in these three populations were ChangJiang 0.108%, MinJiang 0.843%, and ZhuJiang 0.097%. MinJiang is also the largest among these three populations. Genetic distances were between 0.1 and 0.9% within populations and 0.5 to 1.9% between populations. The largest genetic distance was the 1.9% between the ChangJiang and MinJiang populations, and the smallest was 0.5% between the MinJiang and the ZhuJiang populations. AMOVA analysis disclosed that variation among populations accounts for 74.61% of total variation, suggesting that this is the main source of total variation. The results of this study suggest that the three Coilia mystus populations, especially the most isolated Changjiang population, have developed significant genetic structure.

Coilia ectenes is a commercially important fishery species. In this study, genetic diversity and population structure of C. ectenes were examined by using mitochondrial DNA control region sequences in 246 individuals sampled from 10 localities in China. One hundred and ninety-five polymorphic sites defined 184 distinct haplotypes, revealing a moderately high haplotype diversity (Hd) and a relatively low nucleotide diversity (π) in the 10 localities. An excess of unique haplotypes at most sample locations were detected, which might influence the genetic structure of the C. ectenes populations. Hd ranged from 0.939 to 1.000 and π ranged from 0.26% to 1.15%. The Dongting fish population had the highest π level. The genetic distances ranged from 0.26% to 1.03% within populations and from 0.56% to 4.90% between populations. The distances between the Fuzhou (FZ) population and other populations were mostly >4.8%. Neighbor-joining tree indicated distinct patterns of phylogeographic structure among haplotypes from FZ population and those from other populations. Analyses of molecular variance and F(st) statistics suggested that the divergence existed among populations from 10 localities, indicating that gene flow might be restricted among those regions, despite the wide dispersal. In addition, neutral tests and analysis of mismatch distribution suggested that C. ectenes might have undergone a population expansion. Our study revealed the extant population genetic diversity and structure of the C. ectenes, and was in favor of the related fishery management issues including fishery stock identification and conservation.