Complete mitochondrial genome of Whitmania laevis (Annelida, Hirudinea) and comparative analyses within Whitmania mitochondrial genomes

The complete mitochondrial genome of Whitmania laevis is 14,442 bp in length and contains 37 genes including 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes. The almost-complete mitochondrial genome of Whitmania acranulata, consisting of 13,494 bp, contains 35 genes including 13 PCGs, 20 tRNA genes, and two rRNA genes. COI phylogenetic analyses showed that the samples reported in GenBank and analysed as Hirudo nipponia KC667144, Hirudinaria manillensis KC688268 and Erpobdella octoculata KC688270 are not the named species and they should belong to Whitmania. We compared and analyzed the characteristics of nucleotide composition, codon usage, and secondary structures of 22 tRNAs and two rRNAs from Whitmania taxa. Moreover, we analyzed phylogenetic relationships of Annelida using maximum likelihood (ML) and Bayesian inference (BI) methods, based on 11 mitochondrial genes. Our results reveal that W. laevis has a close relationship with W. pigra.