Use Of Mitochondrial Dna Sequence Analysis Of The Liaodong Bay, The Harbor Seal Population Genetic Structure

Spotted seals (phoca largha) called Western Pacific Cod Seal,belong to Carnivora,Caniformia,Phocidae,Phoca,They are second-class protection animals of China. Spotted Seals are the only pinniped animals living and reproducing in china sea,and Liaodong Guif of Bohai Sea is one of the eight breeding area of Spotted seals around the world.In this paper, the population structure of spotted seals was investigated using the mitochondrial DNA (mtDNA) sequences.15 segments of 625bp length mtDNA of Spotted seal (phoca largha) were sequenced by direct sequencing of PCR products method. In all of the 15 sequences, there is one C/T transition in gene ND4L. Compared with Spotted seal ND4L sequence in GenBank, no base changed in tRNA-ARG except two transitions in ND4L.The phylogenetic analysis of 22 ND4L sequences of Phocidae from GenBank showed that there are two clades (which belong to Northern Group and Southern Group) supported by relatively high bootstrap value and there are more closed relationship between spotted seal and harbor seal.17 haplotypes with 717bp were obtained from the mtDNA control region, adjacent proline and a portion of the threonine tRNA genes of 46 individuals. All of the 17 haplotype sequences of spotted seals have two deletions in the mtDNA control region, compared with that of harbor seals, which prove to be a useful species-specific marker between spotted seals and harbor seals. Compared with spotted seals along Sea of Japan and Sea of Okhotsk, Spotted seals of Liaodong Guif had one base insertion at site 16296 of mtDNA, which prove to be marker between these two populations. The haplotype diversity of Spotted seals in Liaodong Guif (0.006±0.002) was much lower than that spotted seals in Sea of Japan(0.020±0.004) and Sea of Okhotsk(0.022±0.004), it showed that the genetic structure of spotted seals in Liaodong Guif had a tend to simplify and genotype was relative simple.They may be caused by genetic bottle-neck effect some time in the past. The results from this study showed that the spotted seals of Liaodong Guif is a independent population and no genetic exchanges with those along Sea of Japan and Sea of Okhotsk.Using the ND4L and DJLoop sequences of the Spotted seals of Liaodong Guif identify the unknown sequences, proved the feasibility of using mtDNA sequences for species identification of Spotted seals or related animals.