Abstract
BackgroundBlood-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.ResultsWe identified all of the 37 mitochondrial genes common to animals in Polyplax asiatica and Polyplax spinulosa. The mitochondrial genes of these two rat lice are on 11 circular minichromosomes; each minichromosome is 2–4 kb long and has 2–7 genes. The two rat lice share the same pattern for the distribution of the protein-coding genes and ribosomal RNA genes over the minichromosomes, but differ in the pattern for the distribution of 8 of the 22 transfer RNA genes. The mitochondrial genomes of the Polyplax rat lice have 3.4 genes, on average, on each minichromosome and, thus, are less fragmented than those of the human lice (2.1 and 2.4 genes per minichromosome), but are more fragmented than those of the pig lice (4.1 genes per minichromosome).ConclusionsOur results revealed distinct patterns of mitochondrial genome fragmentation within the genus Polyplax and, furthermore, indicated a possible inverse link between the extent of mitochondrial genome fragmentation and the length of life cycle of the blood-sucking lice.
Highlights
Blood-sucking lice parasitize eutherian mammals with 67% of the 540 described species found on rodents
The sequence-reads are 90 bp each; assembly of these sequence-reads into contigs allowed us to identify all of the 37 mt genes typical of animals in Po. asiatica distributed over 11 minichromosomes (Figure 2A; Table 1)
Each of the 37 mt genes identified in Po. asiatica is present on only one minichromosome; there is no overlap in gene content
Summary
Blood-sucking lice (suborder Anoplura) parasitize eutherian mammals with 67% of the 540 described species found on rodents. Lice in the suborder Anoplura are wingless, exclusive blood-sucking insects and are permanent ectoparasites of eutherian mammals [1,2]. More than 540 species of blood-sucking lice have been described and are classified into 15 families species of mammals that are closely related phylogenetically (up to 39 species) [6]. Adding to their unique, exclusive blood-feeding life style and the high host-specificity (relative to other ectoparasites), recent studies revealed that blood-sucking lice have an unusual, fragmented mitochondrial (mt) genome organization. The domestic pig louse, Haematopinus suis, and the wild pig louse, Haematopinus apri, have their 37 mt genes on nine minichromosomes; each minichromosome has 2–8 genes and is 3–4 kb in size [12]
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