The human body louse (Pediculus humanus) is a common pest found throughout the world. A parasitic organism that feeds on blood, it is a known transmitter of diseases such as typhus and relapsing fever. Until recently lice were known primarily from their infamy but new research first published in Genome Research (http://www.genome.org/) has highlighted a remarkable feature in this species. Having analysed the mitochondrial DNA of the human body louse it has been found to be highly fragmentized. So far this is the first animal species that has shown this unique characteristic.
Normally in animals mitochondrial DNA consists of a circular chromosome that contains 37 genes. The length of this chromosome is ~16 kb long. The mitochondria in the human body louse instead had its DNA and all 37 genes contained in 18 minicircular chromosomes. While this is the first time an animal has been found with multiple mitochondrial "minichromosomes" they have been previously found in plants and some protists.
It has also been found that other blood sucking lice also share this characteristic but the type of lice that feed on the hair or dead skin of animals do not have fragmented mitochondrial chromosomes. This has sparked some discussion among scientists on whether evolution of these minichromosomes had evolved at the same time as these animals begun to feed on blood.
Shao, R., Kirkness, E & Barker, S 2009, 'The single mitochondrial chromosome typical of animals has evolved into 18 minichromosomes in the human body louse, Pediculus humanus' Genome Res. published ahead of print March 31, 2009, viewed 1/4/2009, http://genome.cshlp.org/content/early/2009/03/25/gr.083188.108
'Lice genomes pieces of a new puzzle', media release, 1/4/2009, http://www.biologynews.net/archives/2009/03/30/lice_genomes_pieces_of_a_new_puzzle.html
