| Chu's croaker and Pacific white shrimp are the major commercial species in termsof aquaculture production in China. In the present study, in order to provide data for themanagement and conservation of resource for Chu's croaker and Pacific white shrimpand to provide a basis for future research. Partial sequence of mitochondrial 16S rRNAgene was determined and mitochondrial 16S rRNA gene fragments were amplified from100 Chu's croaker (Nibea coibor) individuals from two hatchery-produced stocks, basedon which PCR-RFLP analysis was conducted to estimate the level of genetic diversitywithin the two stocks of Chu's croaker. Molecular phylogenetic analysis between Chu'scroaker and other species in Sciaenidae was performed as well; Growth traits and geneticdiversity of seven cultured stocks of different generations of Pacific white shrimp wereinvestigated.(1) The PCR products were about 620bp long. PCR products from five individualswere directly sequenced subsequently. After alignment, a fragment of 468bp nucleotidesequence was used for sequence analysis. Five sequences were consisted of twohaplotypes, between which there was only one base substitution. The PCR-RFLPanalysis showed that 98％of 100 individuals from two stocks belonged to one haplotype,2％to another, suggesting that genetic diversity in the two stocks is possibly low. Theaverage base compositions of the two haplotypes were 22.0％, 26.3％, 29.8％, 21.9％forT, C, A and G respectively, with GC content being 48.2％. Alignment with 11homologous sequences from the other 9 species in 7 genera of Sciaenidae in GenBankrevealed 69 parsimony-informative sites, 55 singletons and 16 insertion/deletions among429 aligned sites. Phylogenetic analysis demonstrated that Chu's croaker was closelyrelated to yellow drum (Nibea albiflora), consistent with the morphologicalclassification. (2) Variation of growth traits of body length and body weight was investigated forseven cultured sotcks of four generations of Pacific white shrimp (Litopenaeusvannamei), including Hainan stock (first generation by imported prawns, G1), Shandongand Raoping stocks (G2), Zhanjiang 2 and Zhanjiang 3 stocks (G3), Zhanjiang 1 andShanghai stocks (G4). The average body lengthes (ranges) were 14.76 (13.25-15.99),8.46 (6.28-10.48), 9.24 (4.28-10.70), 7.75 (5.13-9.36), 11.38 (8.13-14.12), 5.25(3.47-6.83) and 7.14 (4.14-9.00) for the seven stocks, respectively, and the coefficients ofvariance (CV) for body length were 0.04, 0.08, 0.08, 0.09, 0.12, 0.14, 0.14, respectively.The average body weights (ranges) were 33.41 (24.33-39.74), 5.19 (1.80-9.68), 6.95(3.18-11.34), 4.62 (1.52-9.87), 15.03 (6.00-26.96), 1.47 (0.48-3.42) and 3.29 (0.49-6.20),respectively, and the CVs for body weight were 0.10, 0.23, 0.21, 0.27, 0.32, 0.39, 0.36,respectively. The CVs of body length and body weight increased from generation togeneration, and nearly 10％increment per generation was observed for CV of bodyweight. The CV for the first generation was similar to that of parental stock selected inthe USA. The correlation coefficient between body length and body weight wassignificant in each stock (P＜0.01). The regression equation for body weight and bodylength was W=0.01L2.93 based on all individuals. This study suggests that growth traitsof selected Pacific white shrimp imported from the USA will occur divergent fromgeneration to generation.(3) For microsatellite analysis, 12 pairs of primers were screened out of 21microsatellite primers based on effective amplification. Using these 12 microsatellite loci,10 polymorphic loci were obtained and the percentage of polymorphic loci accounted for83.33％. In 10 polymorphic loci, the total allele number presented was 63. Allele numberwas counted from 2 to 15 at each locus. The negative mean value of D (beterozygotedeficiency of excess) indicated an overall deficit of heterozygotes for seven culturedstocks. 54 out of 70 tests were detected significant deviation from Hardy-Weinbergequilibrum within seven stocks at 10 loci. F(IS) values was plus at nine loci. Pairwise FSTvalues ranged from 0.1489 to 0.3746 and all pairs of stocks are significantlydifferentiated. AMOVA indicated that genetic variation among stocks (27.83％) is lowerthan that within stocks (72.17％). The above analysis indicated that genetic diversity is low in two stocks of Chu'scroaker, Chu's croaker was closely related to yellow drum; For Pacific white shrimp,there are rich genetic information and high genetic diversity level in seven culturedstocks, genetic differentiation within stocks is higher than that among stocks, geneticvariation is great among different generations, with the increase of breeding generations,growth traits seperated and genetic diversity declined.
|
PDF Full Text Request