When does the parasite become you?

Science News: "Louse-y genome surprise
3.30.09 - Blood-sucking body lice store mitochondrial DNA in 18 mini-chromosomes"

Mitochondria are the energy engines of our cells but they began as seperate organisms, bacteria, that invaded ancestral cells and brought this useful talent along. Now, it appears that invaders can become chomosomes.

Study coauthor Ewen Kirkness speculates that the multiple chromosomes may bump up genetic variation. “We see bits of genes being swapped between different circles,” says Kirkness, of the J. Craig Venter Institute in Rockville, Md. This gene mingling may have allowed lice to quickly adapt when something new showed up on the menu: human blood.

Sounds like a horror movie ... Invasion of the Body Snatchers!