Background: Sucking lice (suborder Anoplura, class Insecta) parasitize eutherian mammals and feed exclusively on blood. Sucking lice have one of the most complex mitochondrial genome structure seen in eukaryotes. While eukaryotes typically have a single, circular mitochondrial chromosome with all genes on it, the sucking lice investigated so far have their mitochondrial genes scattered over 9 to 20 mini-chromosomes. Most mini-chromosomes have only one gene or a few genes. Furthermore, the mitochondrial genome structure varies from species to species even in the same genus. Aims: This study aims to understand how the complex mitochondrial genomes of sucking lice evolved. Methods: We sequenced the mitochondrial genome of the guanaco louse, Microthoradus praelongiceps, and compared it with other sucking lice that infest humans, chimpanzees, pigs, horses and rats. Research findings: The mitochondrial genome of the guanaco louse has 37 genes on 12 mini-chromosomes. The guanaco louse resembles the rat lice much more than the human lice, chimpanzee lice, pig lice and horse lice in its mitochondrial genome structure. However, phylogenetic analyses of mitochondrial genome sequences revealed that the guanaco louse is more closely related to the human lice, chimpanzee lice, pig lice and horse lice than to the rat lice. Thus, the common features in mitochondrial genome structure shared between the guanaco louse and the rat lice can be inferred to be ancestral to all sucking lice according to the principle of parsimony. By comparison to the ancestral features of sucking lice, it is clear that at least 4 mini-chromosomes have split in the lice of humans and chimpanzees, whereas at least 6 mini-chromosomes have merged in the lice of pigs and horses. We conclude that both split and merge of mini-chromosomes played major roles in shaping the complex mitochondrial genomes of the sucking lice.
2015 University Research Conference: Integrate, Innovate, Inspire, Sunshine Coast, Australia 13-16 July 2015