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Open Access Research article

Fragmented mitochondrial genomes are present in both major clades of the blood-sucking lice (suborder Anoplura): evidence from two Hoplopleura rodent lice (family Hoplopleuridae)

Wen-Ge Dong12, Simon Song3, Xian-Guo Guo1*, Dao-Chao Jin2, Qianqian Yang4, Stephen C Barker5 and Renfu Shao3*

Author Affiliations

1 Institute of Pathogens and Vectors, Dali University, and Yunnan Provincial Key Laboratory for Zoonosis Control, Dali, China

2 Institute of Entomology, Guizhou University, and the Provincial Key Laboratory for Agricultural Pest Management in Mountainous Region, Guiyang, China

3 GeneCology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland, Australia

4 College of Agronomy and Biotechnology, China Agricultural University, Beijing, China

5 Parasitology Section, School of Chemistry and Molecular Biosciences, University of Queensland, Queensland, Australia

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BMC Genomics 2014, 15:751  doi:10.1186/1471-2164-15-751

Published: 2 September 2014

Abstract

Background

The suborder Anoplura contains 540 species of blood-sucking lice that parasitize over 840 species of eutherian mammals. Fragmented mitochondrial (mt) genomes have been found in the lice of humans, pigs, horses and rats from four families: Pediculidae, Pthiridae, Haematopinidae and Polyplacidae. These lice, eight species in total, are from the same major clade of the Anoplura. The mt genomes of these lice consist of 9–20 minichromosomes; each minichromosome is 1.5–4 kb in size and has 1–8 genes. To understand mt genome fragmentation in the other major clade of the Anoplura, we sequenced the mt genomes of two species of rodent lice in the genus Hoplopleura (family Hoplopleuridae).

Results

We identified 28 mt genes on 10 minichromosomes in the mouse louse, Ho. akanezumi; each minichromosome is 1.7–2.7 kb long and has 1–6 genes. We identified 34 mt genes on 11 minichromosomes in the rat louse, Ho. kitti; each minichromosome is 1.8–2.8 kb long and has 1–5 genes. Ho. akanezumi also has a chimeric minichromosome with parts of two rRNA genes and a full-length tRNA gene for tyrosine. These two rodent lice share the same pattern for the distribution of all of the protein-coding and rRNA genes but differ in tRNA gene content and gene arrangement in four minichromosomes. Like the four genera of blood-sucking lice that have been investigated in previous studies, the Hoplopleura species have four minichromosomes that are only found in this genus.

Conclusions

Our results indicate that fragmented mt genomes were present in the most recent common ancestor of the two major clades of the blood-sucking lice, which lived ~75 million years ago. Intra-genus variation in the pattern of mt genome fragmentation is common in the blood-sucking lice (suborder Anoplura) and genus-specific minichromosomes are potential synapomorphies. Future studies should expand into more species, genera and families of blood-sucking lice to explore further the phylogenetic utility of the novel features associated with fragmented mt genomes.

Keywords:
Mitochondrial genome; Genome fragmentation; Minichromosome; Chromosome evolution; Sucking lice