Most animals reproduce sexually. A female's egg is fertilized by a male's sperm. But sometimes this doesn't happen. Some species of insects, fish, or reptiles don't need to mate to produce offspring. It has even been observed in a captive crocodile at a zoo in Costa Rica. The phenomenon is called virgin birth or parthenogenesis, and involves the egg developing into an embryo without the intervention of a male. A group of scientists has for the first time identified the genetic cause of virgin birth. Even more astonishing, they have managed to induce it in the fruit fly, a creature that reproduces sexually. But the story doesn't end there: once activated, this ability is passed on from generation to generation. Offspring can reproduce sexually if there are males around, or by parthenogenesis if there are none. The resulting children are not exact clones of their mother, but they are genetically very similar and are always female. "We are the first to show that virgin births can be engineered to happen in an animal. It was very exciting to see a virgin fly produce an embryo capable of developing to adulthood and then repeating the process," says Alexis Sperling, a researcher at the University of Cambridge and first author of the article, published in the journal Current Biology. Related News standard No This grasshopper has gone 250,000 years without sex and is doing great Judith de Jorge Reproduction by cloning has not prevented this insect from being successful and spreading throughout Australia In the experiments, the flies' behavior was quite significant. "In our genetically manipulated flies, the females waited to find a male for half their lives, about 40 days, but then gave up and proceeded to have a virgin birth," says the researcher. In other words, when they saw that their chances of having a mate were very small, they decided to manage on their own. It is also true that they were not many. Only the 1-2% second-generation female flies with the ability to give birth virgins produced offspring, and this occurred only when no male flies were around. When males were available, the females mated and reproduced normally. According to the researchers, switching to virgin birth may be a survival strategy: A single generation of virgin births may help keep the species going. To achieve their results, the researchers first sequenced the genomes of two strains of another fruit fly species, called Drosophila mercatorum. One strain needs males to reproduce, the other reproduces only through virgin birth. They identified genes that were turned on or off when the flies reproduced without fathers. With the candidate genes for virgin birth ability identified in Drosophila mercatorum, the researchers altered what they thought were the corresponding genes in the fruit fly model, Drosophila melanogaster. It worked: Drosophila melanogaster suddenly acquired the ability to perform a virgin birth. The research involved more than 220,000 virgin flies and took six years to complete. Pest beware For the scientists, the key to the discovery was the fact that this work was done in Drosophila melanogaster; according to them, it would have been incredibly difficult in any other animal. This fly has been the “model organism” for genetics research for more than 100 years, and its genes are very well understood. Sperling hopes to investigate why virgin birth in insects may be becoming more common, particularly in pest species. “If there is continued selection pressure for virgin births in insect pests, which there appears to be, it will eventually lead to them reproducing only in this way. It could become a real problem for agriculture because females only produce females, so their ability to propagate doubles,” the researcher notes. MORE INFORMATION news No The two oldest known families discovered: up to seven generations without a trace of infidelity news No A never-before-seen worm resurrected after spending 46,000 years frozen under ice in Siberia Females of some egg-laying animals, including birds, lizards, and snakes, can naturally change to give birth without males. But virgin birth in animals that normally reproduce sexually is rare, often only seen in zoo animals, and usually occurs when the female has been isolated for a long time and has little hope of finding a mate.
