The first complete mitochondrial genome of the genus Echinolaelaps reveals mitochondrial genome rearrangement type and evolution of Gamasida.

Echinolaelaps echidninus is a gamasid mite that is of medical and veterinary significance as parasites and vectors of disease agents, which can carry pathogens of zoonosis such as Rickettsia tsutsugamushi, Rickettsia Q fever, Rickettsia mooseri, Rickettsia pox pathogens, Corynebacterium pseudotuberculosis and Leptospira. At present, only single mitochondrial genes have been analysed for E. echidninus in the world, and no complete mitochondrial genome has been reported. However, information carried by a single gene is limited. Therefore, the complete mitochondrial genome of E. echidninus was determined for the first time by Illumina Hiseq X-Ten platform in this study. The mitochondrial genome is 15 736 bp in length and contains 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region of 1561 bp in length. Codon analysis of 13 protein-coding genes revealed that UUU, UUA, AUU, AUA and AAU were the most frequently used, while cox2 had the fastest evolutionary rate and cob the slowest. Comparative analysis of genome structure and breakpoint distances of the mitochondrial genomes of 23 species in 17 genera from 10 families of Gamasida deposited in GenBank revealed a novel gene arrangement type of the E. echidninus mitochondrial genome, and different degrees of rearrangement among different taxa of Gamasida. Phylogenetic analyses of Gamasida were performed using the maximum likelihood and Bayesian inference methods. Echinolaelaps echidninus was clustered with Dermanyssoidea and formed a more supportive sister group with Varroa destructor. This study provides novel insights into rearrangement patterns and evolution of mitochondrial genomes of Gamasida.