# The Complete Mitogenome of Haemaphysalis parva (Arachnida: Ixodidae) and Comparative Mitogenomics of Haemaphysalis Species

## TL;DR

This paper reports the complete mitochondrial genome of Haemaphysalis parva, a tick species that can transmit diseases, and compares it with other Haemaphysalis species to understand their genetic structure and evolution.

## Contribution

The study provides the first complete mitogenome of Haemaphysalis parva and identifies lineage-specific features through comparative analysis.

## Key findings

- The mitogenome of H. parva is 14,843 bp and contains 37 canonical genes and two non-coding regions.
- Several genes show signs of positive selection, indicating adaptive evolution in this tick species.
- Comparative analysis reveals a rearranged gene block and conserved sequence blocks, including a putative humanin-like ORF.

## Abstract

Introduction

Ticks are globally recognised as the second most important vectors of infectious diseases, posing significant threats to human and animal health. Haemaphysalis parva (Acari: Ixodidae) is frequently reported infesting humans and domestic animals and has been experimentally demonstrated to transmit Babesia ovis, with field associations to ovine babesiosis during the colder months. It has also been reported to harbour several zoonotic pathogens, including Coxiella burnetii, Francisella tularensis, and various Rickettsia species. Here, we aim to report the complete mitochondrial genome of Haemaphysalis parva (Ixodida: Ixodidae), a zoonotic tick species with significant public health relevance in Türkiye.

Methods

For this purpose, we isolated total genomic DNA from H. parva and sequenced using Illumina HiSeq 2000 platform, raw reads were processed, and then the mitogenome was assembled using the Geneious R9 program with “map to reference” and verified via “de novo assembly” options.

Results and Discussion

The mitogenome of H. parva is a circular DNA molecule of 14,843 bp, comprising the canonical 37 genes (13 PCGs, 22 tRNAs, and 2 rRNAs) and two major non-coding regions (312 bp and 304 bp). Strand-specific compositional bias revealed a strong A + T enrichment (77.8%) and pervasive negative AT- and GC-skew values, diverging from the typical skew profiles observed in most arthropods and possibly reflecting lineage-specific replication asymmetries. All PCGs exhibited AT-biased codon usage, preferentially encoding hydrophobic amino acids. Several genes (cox1, cytB, nd2, nd6) showed dN/dS ratios > 1, suggesting positive adaptive evolution. Comparative mitogenomic analysis of 27 Haemaphysalis species confirmed overall structural conservation but identified a rearranged nd1–rrnS gene block relative to the Ixodes reference genome. Collinearity and synteny analyses revealed multiple conserved sequence blocks, including a putative humanin-like ORF within the rrnL gene region, indicating potential dual-coding or regulatory elements within non-PCG regions.

The online version contains supplementary material available at 10.1007/s11686-026-01243-y.