Scientists have found an unprecedented evolutionary modification deep within the cells of the lowly human body louse (__Pediculus humanus__): the tiny blood sucker contains not one but 18 separate mitochondrial chromosomes.
A female human body louse (__Pediculus
humanus corporis__).

Photo courtesy of Richard Webb
and Renfu Shao
"It's a big surprise to me and my colleagues," wrote linkurl:Renfu Shao,; lead author of the newly published __Genome Research__ paper describing the discovery, in an email to __The Scientist__. "Since the human mitochondrial genome was linkurl:sequenced; in 1981, more than 1500 animals have been sequenced for complete mitochondrial genomes," he wrote. With the exception of some oddball ciliates, flagellates and cnidarians, virtually all animals have a single, circular mitochondrial chromosome that contains approximately 37 genes. "Thus, it has almost been taken for granted that any animals would have a single mitochondrial chromosome with all mitochondrial genes on it." linkurl:David Rand,; a Brown...

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