Complete mitochondrial genome of Hirudo nipponia (Annelida, Hirudinea).

The complete mitochondrial genome (14,414 bp) of the blood-feeding leech Hirudo nipponia, which was an important natural medicinal resource, was sequenced and characterized. The genome encodes 13 protein-coding genes, 2 rRNAs and 22 tRNAs. The content of A + T was 72.60% for H. nipponia (31.69% A, 40.91% T, 15.45% G and 11.95% C). All protein-coding genes started with ATN except for nad3 and nad5, which used GTG as start codon. Eight protein-coding genes stopped with termination codon TAA. Five protein-coding genes used incomplete stop codon TA or T. The A + T-rich region was located between tRNA-Arg and tRNA-His with a length of 83 bp. This is the first report about completely sequenced mitochondrial genome from the family Hirudinidae. The complete mitochondrial genomes of H. nipponia would be useful for the exploration of Hirudinea polygenetic relationships.