Mitochondrial genomes of the human broad tapeworms Diphyllobothrium latum and Diphyllobothrium nihonkaiense (Cestoda: Diphyllobothriidae).

Mitochondrial DNA (mtDNA) sequences of the human broad tapeworms Diphyllobothrium latum and Diphyllobothrium nihonkaiense have been totally determined. Both of them are closed circular molecules (total length, 13,720 bp in D. latum and 13,747 bp in D. nihonkaiense) containing genes for 12 proteins, 22 transfer RNAs, and two ribosomal RNAs. All the genes are coded on T-rich strand. The gene order of Diphyllobothrium mtDNAs is completely identical with that of Taenia and Echinococcus mtDNAs. The overall A + T contents of the genomes are 68.3% in D. latum and 67.8% in D. nihonkaiense. The pairwise divergence values of nucleotide sequences between these tapeworms ranged from 0.069 to 0.152 in protein-coding genes, demonstrating that D. nihonkaiense is a distinct species. The sequences determined in this study may provide useful marker systems for diagnostic, epidemiological, and phylogeographical studies of human diphyllobothriasis.