Morphologic Characters And Genentic Diversity Among Three Wild Populations Of Siniperca Kneri

Siniperca kneri, a fleshy delicate important famous farmed freshwater fish with delicious taste and rich nutrients, is a species of Perciformes, Serranida, Sinipercinae, Siniperca. The fish, commonly known as Mandarin Fish or Baigui, is widely distributed in Yangtze River and Southern China river systems. As an endemic fish to southern China, its growth rate is slower than Siniperca chuatsi but faster than the other Siniperca kinds. Guizhou province located in the transitional belt zone between Diandong plateau and Xiangxi hilly, which is in the upper reaches of the Yangtze River and the Pearl River, and the area is a typical Karst mountainous topography. In the province, Siniperca kneri is an important wild economic fish that mainly distributed in Wujiang river, Chishui river, Jinjiang river, Songtao river and Qingshui river(Yangtze River Basin), Duliu river and Hongshui river(Pearl River Basin). As an important local wild economic fish, the resource was under threaten. At the present, the S. kneri in the National Aquatic Germplasm Resources Conservation Area of the province still lack of the most basic morphological parameters, also known little background information in population genetic structure and genetic diversity aspects. Thus, the resources superiority didn't bring up the due economic benefit. In this paper, basing on the data of morphology and framework measurements, cytochrome coxidase subunit I, control region complete sequence and first ribosomal internal transcribed spacer complete sequence to study the morphological diversity and genetic diversity of S. kneri that collected from Yangtze River Basin and Pearl River Basin in Guizhou province.The major results are as following,1. Combining the traditional morphological and framework measurements data, and used multivariate analysis methods to analyze morphological differences among the three wild populations(JTD: Tongren of Beipanjiang River, WYD: Yanhe of Wujiang River, BGD: Guanling of Beipanjiang River). Result showed: as meristic characters, highly significant differences between JTD and WYD in anal fin spines, highly significant differences between JTD and BGD in pectoral fin rays, anal fin rays, caudal fin rays, highly significant difference between WYD and BGD in pectoral fin rays, ventral fin ray, caudal fin rays. Meristic characteristics data showed that JTDpopulation had the minimum eyes, maximum snout and the lowest body height; WYD population had the maximum eyes, meanwhile, the distance between the eyes was shortest, had the thinnest body and the shortest caudal peduncle; BGD population had a highest and thickness body, with a minimum snout, the distance between the eyes was longest and had the longest caudal peduncle. The clustering analysis showed that the JTD and WYD populations clustered first and then clustered with the BGD population, it may indicated that the morphological characters of JTD population was similar to WYD population. The discriminant functions of these three populations were established basing on stepwise discriminant analysis and its comprehensive discrimination rate reached 91.2%. The principal component analysis yielded six principal components with a cumulative contribution ratio of 72.431%. Comprehensive all the results showed that JTD and WYD were more similarity than with BGD population. The distance of geographic distribution and the difference living environment maybe the factor that drive to the variation of those changes.2. The partial mitochondrial COI sequences of 169 individuals of S. kneri from three populations were amplified by PCR technique to analyze their sequence variation, and 1512 bp nucleotide sequences were obtained.The results showed that the average contents A, T, G and C were 24.9%, 28.6%, 28.7%, 17.8% and 23.6%, respectively, the average contents of AT(53.5%) were obviously higher than that of G C(46.5%). Five variable sites were detected and 5 different haplotypes were defined in 169 samples. Ten variable locus were detected between the two populations of S. kneri in Guizhou and S. kneri in Dongting lake, and most of them were occurred from 1268 nt to 1456 nt. There were no difference about codon usage among those three populations in Guizhou. Comparing with Dongting lake S. kneri, there were no significant differences in the first positions of codon usage, the content of T(40.9%) was higher than the latter(39.9%), whereas, in the second codon positions, the content of A and C was lower than the latter. There was small discriminatory of codon usage between S. kneri populations in Guizhou and in Dongting lake. But comparing to S. scherzeri, S. obscura, S. roulei and S. undulata, they were revealed different discriminatory at the first codon positions and the third codon positions, especially the content of A(30.0%) of S. obscura and S. undulata at the first codon positions was significantly lower than that of S. kneri in Guizhou(31.8%), whereas, G content(8.9%) of S. undulata was significantly higher than the latter(7.3%). The total haplotype diversity(Hd) was 0.395 and nucleotide diversity(Pi) was 0.00029, therefore, there was a low genetic diversity level in the three populations of S. kneri.3. PCR and DNA sequencing technology were used to compare the DNA sequence of mitochondrial control regions among these three Siniperca kneri populations. The results showed that the sequence length of the D-Loop regions were various from 828-833 bp, and there was small difference in sequence length. All kinds of base content were nearly the same among three populations, the average content of A was the highest, G was the lowest, and the content of AT was much higher than that of CG. 13 polymorphic sites were found out in these populations and 5 haplotypes were defined, and Hap1 was the share haplotype which represented 174 individuals(92% of the total samples). The haplotype diversity(Hd) and nucleotide diversity(Pi) of WYD population were higher than the other two. In total, genetic diversity was low in the three populations. There was low genetic differentiation, certain gene exchange and moderate genetic differentiation between JTD population and WYD population. Because of the geographic isolation, BGD population was lack gene exchange with the other two populations.4. The sequences analyzed results of 151 individuals internal transcribed spacer 1(ITS-1) of S. kneri in three wild populations showed that: the length polymorphism was detected in three populations of Siniperca kneri, with two mainly 753 bp and 755 bp types in length; the average contents of GC were significant higher than AT; 6 polymorphism loci and 6 haplotypes were detected. The whole three populations of S. kneri showed low genetic diversity, the total haploid type diversity was 0.622, suggesting an abundant genetic diversity in three populations of S. kneri. Four kinds of microsatellites sequences(GC)n?(CT)n?(CG)n?(TCG)n were respectively found in ITS-1 sequences, the(GC)n type had highest frequency. To these three populations, there was gene exchange and weak genetic differentiation between JTD and WYD population; BGD population had big genetic differentiation and lack gene exchange with the other two populations.In short, no matter of the morphological marker or molecular marker, the analyzed of the three S. kneri populations that distributed in the national aquatic germplasm resources conservation area of Guizhou province showed that the morphological and genetic variation that due to the different living environment and longtime geographical isolation, little differentiation and small variation occurred between JTD and WYD population, BGD population had a big variation in degree. The genetic diversity of these three geographical populations was not abundant, WYD population had a higher level than the other two.