No animal has gone completely without sex for as long as bdelloid rotifers, who have been celibate for millions of years. The always female, translucent, and half-a-millimeter long creatures perplex evolutionary biologists, who believe that combining the DNA of two parents is necessary to create the genetic diversity that animal populations need to adapt to a changing environment. (Bacteria manage to diversify without sex because genes can easily jump from one bacterium to another.) Yet with more than 460 species, bdelloid rotifers have managed to survive and diversify over evolutionary time too. So how do they do it? They may do it by "stealing" genes from other organisms. Reporting online today in Nature, researchers have found that the genome of the bdelloid rotifer Adineta vaga (electron microscope image, above) contains an unusual amount of DNA from other organisms that appears to have "jumped" in through a process called horizontal gene transfer that occurs often in asexual bacteria, but very rarely in animals. About 8% of Adineta's genes derive from bacteria and other nonanimal kingdoms of life. The authors suggest that fraction helps keep their populations genetically diverse and adaptable—no whoopee required.
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