Abstract

BackgroundBlood-sucking lice in the genera Pediculus and Pthirus are obligate ectoparasites of great apes. Unlike most bilateral animals, which have 37 mitochondrial (mt) genes on a single circular chromosome, the sucking lice of humans have extensively fragmented mt genomes. The head louse, Pediculus capitis, and the body louse, Pe. humanus, have their 37 mt genes on 20 minichromosomes. The pubic louse, Pthirus pubis, has its 34 mt genes known on 14 minichromosomes. To understand the process of mt genome fragmentation in the sucking lice of great apes, we sequenced the mt genome of the chimpanzee louse, Pe. schaeffi, and compared it with the three human lice.ResultsWe identified all of the 37 mt genes typical of bilateral animals in the chimpanzee louse; these genes are on 18 types of minichromosomes. Seventeen of the 18 minichromosomes of the chimpanzee louse have the same gene content and gene arrangement as their counterparts in the human head louse and the human body louse. However, five genes, cob, trnS1, trnN, trnE and trnM, which are on three minichromosomes in the human head louse and the human body louse, are together on one minichromosome in the chimpanzee louse.ConclusionsUsing the human pubic louse, Pt. pubis, as an outgroup for comparison, we infer that a single minichromosome has fragmented into three in the lineage leading to the human head louse and the human body louse since this lineage diverged from the chimpanzee louse ~6 million years ago. Our results provide insights into the process of mt genome fragmentation in the sucking lice in a relatively fine evolutionary scale.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1843-3) contains supplementary material, which is available to authorized users.

Highlights

  • Blood-sucking lice in the genera Pediculus and Pthirus are obligate ectoparasites of great apes

  • We assembled these sequence-reads into contigs and identified all of the 37 mt genes typical of bilateral animals in the chimpanzee louse; these genes are on 18 types of minichromosomes (Fig. 1; Table 1)

  • Cob-trnS1-trnN-trnEtrnM minichromosome of the chimpanzee louse is not seen in the human head louse and the body louse; the five genes on this minichromosome are on three minichromosomes in the two human lice

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Summary

Introduction

Blood-sucking lice in the genera Pediculus and Pthirus are obligate ectoparasites of great apes. Unlike most bilateral animals, which have 37 mitochondrial (mt) genes on a single circular chromosome, the sucking lice of humans have extensively fragmented mt genomes. The head louse, Pediculus capitis, and the body louse, Pe. humanus, have their 37 mt genes on 20 minichromosomes. To understand the process of mt genome fragmentation in the sucking lice of great apes, we sequenced the mt genome of the chimpanzee louse, Pe. schaeffi, and compared it with the three human lice. The head louse, lives on human head hair and is still prevalent in many countries, in school-aged children. Not as prevalent as the head lice, body lice are healthily more important as they are vectors for three pathogens that cause trench fever, recurrent fever and epidemic typhus in humans [12].

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