Geographical variation of the liver fluke, Clonorchis sinensis, from Korea and China based on the karyotypes, zymodeme and DNA sequences

Abstract

Genetic characterization was carried out in order to reveal the geographical variations of the oriental liver fluke, Clonorchis sinensis (Trematoda: Opisthorchiidae), collected in Korea and China. The chromosome number was 2n=56 in both Korean (Kimhae) and Chinese (Liaoning) flukes, and chromosomes were divided into two groups based on their sizes; consisting of 8 pairs of large and 20 pairs of small chromosomes. However, the karyotypes showed some differences between Korean and Chinese flukes. Isozyme analysis showed that two loci from each enzyme of aconitase and esterase (alpha-Na and beta-Na); only one locus each from six enzymes, glucose-6-phosphate dehydrogenase (G6PD), alpha-glycerophosphate dehydrogenase (GPD), 3-hydroxybutyrate dehydrogenase (HBDH), malate dehydrogenase (MDH), phosphoglucose isomerase (PGl) and phosphoglucomutase (PGM). Most of loci in two populations of C. sinensis showed homozygous monomorphic banding patterns and one of them, GPD was specific as genetic markers between two different populations. Two populations were very closely clustered within the range of genetic identity value of 0.998-1.0. We also compared patterns of intraspecific polymorphism of two markers with contrasted modes of evolution, nuclear ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) of the liver fluke from Kimhae, Guangxi and Liaoning. They showed a high homology. In conclusion, three populations of C. sinensis from Korea and China showed high homogeneity in the nucleotide sequences of the 18S rDNA, ITS2 and mtCOI gene.