Blood-sucking lice (suborder Anoplura) parasitize eutherian mammals with 67% of the 540 described species found on rodents. The five species of blood-sucking lice that infest humans and pigs have fragmented mitochondrial genomes and differ substantially in the extent of fragmentation. To understand whether, or not, any life-history factors are linked to such variation, we sequenced the mt genomes of Polyplax asiatica and Polyplax spinulosa, collected from the greater bandicoot rat, Bandicota indica, and the Asian house rat, Rattus tanezumi, respectively.

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). 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. 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.

Fleas are the most important insect vectors that parasitize warm-blooded animals and are known vectors of zoonotic pathogens. A recent study showed that Stenoponia polyspina parasitizing Eospalax baileyi in Zoige County have carried Bartonella spp. and Spotted fever group Rickettsia (SFGR). Accurate identification and differentiation of fleas are essential for prevention and control of zoonotic pathogens. To understand phylogenetic relationship of the subfamily Stenoponiinae, we described morphological characteristics of S. polyspina and sequenced its mitogenome with 14,933 bp in size and high A + T content (~ 79%). The S. polyspina mitogenome retained the ancestral pattern of mitochondrial gene arrangement of arthropods without rearrangement. The start codons of 13 protein-coding genes (PCGs) are traditional ATN and the stop codons are TAA or TAG. Anticodon loops of all tRNA genes were 7 bp except for trnL₂ and trnD had anticodon loops with 9 bp and the abnormal anticodon loops may be associated with frameshifting mutation. Genetic distance and Ka/Ks ratios indicated that all 13 PCGs of S. polyspina were subjected to purifying selection, with cox1 at the slowest rate and atp8 at the fastest rate. The mitogenomes of 24 species representing 7 families in the order Siphonaptera were selected to reconstruct phylogenetic tree based on concatenated nucleotide sequences of two datasets (PCGRNA matrix and PCG12RNA matrix) using Bayesian inference (BI) and Maximum likelihood (ML) methods. Phylogenetic tree supported that the superfamilies Ceratophylloidea, Vermipsylloidea, Pulicoidea were monophyletic and the superfamily Hystrichopsylloidea was paraphyletic. The family Ctenophthalmidae was monophyletic in PCGRNA-ML (codon partition) and paraphyletic in the remain trees. S. polyspina belongs to the subfamily Stenoponiinae was closely more related to the subfamily Rhadinopsyllinae. This paper explored phylogenetic position of diverse clades within the order Siphonaptera based on morphological and mitogenome data of S. polyspina. Our research enriched NCBI database of the order Siphonaptera.

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.

For the first time, the complete mitochondrial genome of Parasitus fimetorum was sequenced. The mitochondrial genome is 14,619 bp in length and includes 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region. The base composition is 35.6% for A, 34.8% for T, 18.2% for G, and 11.4% for C. A phylogenetic tree based on the maximum likelihood (ML) method indicated that Parasitus fimetorum was clustered with Parasitus wangdunqingi within the family Parasitidae.

Laelapinae mites are involved in transmission of microbial diseases between wildlife and humans, with an impact on public health. In this study, 5 mite members in the subfamily Laelapinae (laelapin mites; LM) were morphologically identified by light microscopy, and the phylogenetic relationship of LM was analyzed in combination with the sequence information of part of the LM cytochrome oxidase subunit I (cox1) gene. The morphological identification revealed that 5 mites belonged to the genera Laelaps and Haemolaelaps, respectively. Sequence analysis showed that the ratio of non-synonymous mutation rate to synonymous mutation rate of LM was less than 1, indicating that the LM cox1 gene had undergone purifying selection. Phylogenetic analysis showed that the Laelapinae is a monophyletic group. The genera Haemolaelaps and Hyperlaelaps did not separated into distinct clades but clustered together with species of the genus Laelaps. Our morphological and molecular analyses to describe the phylogenetic relationships among different genera and species of Laelapinae provide a reference for the improvement and revision of the LM taxonomy system.