Characterization of the complete mitochondrial genome and phylogenetic analyses of Haemaphysalis tibetensis Hoogstraal, 1965 (Acari: Ixodidae)

Abstract

Ticks are specialized ectoparasites that feed on blood, causing physical harm to the host and facilitating pathogen transmission. The genus Haemaphysalis contains vectors for numerous infectious agents. These agents cause various diseases in humans and animals. Mitochondrial genome sequences serve as reliable molecular markers, forming a crucial basis for evolutionary analyses, studying species origins, and exploring molecular phylogeny. We extracted mitochondrial genome from the enriched mitochondria of Haemaphysalis tibetensis and obtained a 14,714-bp sequence. The mitochondrial genome consists of 13 protein-coding genes (PCGs), two ribosomal RNA, 22 transfer RNAs (tRNAs), and two control regions. The nucleotide composition of H. tibetensis mitochondrial genome was 38.38 % for A, 9.61 % for G, 39.32 % for T, and 12.69 % for C. The A + T content of H. tibetensis mitochondrial genome was 77.7 %, significantly higher than the G + C content. The repeat units of H. tibetensis exhibited two identical repeat units of 33 bp in length, positioned downstream of nad1 and rrnL genes. Furthermore, phylogenetic analyses based on the 13 PCGs indicated that Haemaphysalis tibetensis (subgenus Allophysalis) formed a monophyletic clade with Haemaphysalis nepalensis (subgenus Herpetobia) and Haemaphysalis danieli (subgenus Allophysalis). Although the species Haemaphysalis inermis, Haemaphysalis kitaokai, Haemaphysalis kolonini, and Haemaphysalis colasbelcouri belong to the subgenus Alloceraea, which were morphologically primitive hemaphysalines just like H. tibetensis, these four tick species cannot form a single clade with H. tibetensis. In this study, the whole mitochondrial genome sequence of H. tibetensis from Tibet was obtained, which enriched the mitochondrial genome data of ticks and provided genetic markers to study the population heredity and molecular evolution of the genus Haemaphysalis.

Keywords

• Haemaphysalis tibetensis
• Repeat units
• Mitochondrial genome
• Phylogenetic tree
• Hard ticks