Sexless Sea Creatures Steal Foreign Genes

Bdelloid rotifers have maintained a celibate aquatic existence for 80 million years. They are an all-female type of small invertebrates that occasionally produce a child via asexual reproduction—a clone breaks off directly from the mother. But bdelloids have not only survived through the ages, they've managed to evolve and diversify without the genetic intermingling that comes along with sex. Now Harvard University biologists think they have figured out the bdelloid's trick. In a study published today in Science, the research team, led by Eugene Gladyshev, wrote that bdelloids can take DNA not only from other members of their own species, but also from bacteria, fungi, and even plants. When its freshwater habitat temporarily dries up, a bdelloid's cellular membranes break and its genome tears apart. But disintegrating DNA isn't enough to kill this hardy creature—when water returns, a bdelloid can pick up its own pieces and put itself back together. According to the Harvard scientists, that fancy bit of reassembly could be the key to the animal's asexual evolution. During the shuffle, the creatures often pick up random bits of DNA from their broken sisters, or from plants and animals in the area. The same bdelloid springs back to life with a slightly altered genome, and it evolves without all the bothers of sex. But if you're a rotifer, what do you do with fungus DNA? The Harvard scientists say they're not sure yet. They found foreign DNA in higher concentrations in the telomeres, regions located at the ends of chromosomes, so perhaps the foreign genes help to keep the DNA strand from unraveling. In any case, if you're planning to swear off sex for 80 million years, you'd better be a crafty genetic thief. Image: Diego Fontaneto