By Amy Maxmen
Members of the only all-girl, asexual class of animals turn out to be loose. Bdelloidea DNA is tangled up with DNA from all dregs of life – animals, plants, bacteria and even fungi. The shocking finding, to be reported in the May 30 Science, may explain how the group has survived without sex for more than 35 million years.
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Sex generates genetic variation because genes in mom’s egg and dad’s sperm meet to form novel combinations in an embryo. But bdelloid invertebrates undergo no such process. Like most rotifers, bdelloids swirl around in freshwater ponds or droplets on moss, eating teensy particles. Some animals that occasionally reproduce asexually can also sometimes produce sexually. But the entire class of bdelloids are always spermless and exclusively female. The ovary-bearing females lay tiny eggs out of which clonal babies hatch.