Abstract:In order to explore the genetic structure of sea cucumber populations with different body color characteristics in different sea areas, 16S rDNA, COⅠ and D-loop gene sequences of eight populations of sea cucumber (Apostichopus japonicus) from China, Korea and Russia were amplified by PCR. Genetic diversity and evolutionary relationship of the 8 populations were analyzed by 16S rDNA, COⅠ and D-loop gene sequences from 80 samples. The results showed that the sequence lengths of 16S rDNA, COⅠ and D-loop genes were 543 bp, 656 bp and 509~527 bp, respectively. There were 16 polymorphic loci and 16 haplotypes in the 16S rDNA sequence, the haplotype diversity index was 0.629, the nucleotide diversity index was 0.0016, and the average nucleotide diversity was 0.880. A total of 62 polymorphic loci and 38 haplotypes were detected in the COⅠ sequence, the haplotype diversity index was 0.958, the nucleotide diversity index was 0.0073, and the average nucleotide diversity was 4.796. A total of 200 polymorphic loci and 61 haplotypes were detected in the D-loop sequence. The haplotype diversity index was 0.992, the nucleotide diversity index was 0.0157, and the average nucleotide diversity was 6.834. The results showed that the polymorphic loci, haplotypes and nucleotide diversity of D-loop and COⅠ sequences were significantly higher than those of 16S rDNA sequences, which were more suitable for the analysis of genetic structure in different populations of the same species. The genetic diversity of the three populations was the highest in the Posco area of South Korea, which may be related to the influence of ocean currents. The COⅠ gene was used to analyze the genetic differentiation of three body color sea cucumbers collected from Posco, the genetic differentiation coefficient Fst was less than 0.05, and there was no genetic differentiation. The results of phylogenetic tree construction using COⅠ gene showed that the Qingdao and Yantai sea cucumber population were clustered into one branch, then the Korean Mokpo black sea cucumber population clustered into one branch, from the inner outward are successively the Russian population and the Korea Posco population. The results showed that the populations with different body colors were poorly differentiated, and the genetic distances and clustering of different populations had the strongest correlation with their geographical distribution.
