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Scientists discover secret of virgin birth
For the first time, scientists have managed to induce virgin birth in an animal that usually reproduces sexually: the fruit fly Drosophila melanogaster.
Fruit fly, Drosophila mercatorum. Photo: Jose Casal and Peter Lawrence
Once induced in this fruit fly, this ability is passed on through the generations: the offspring can reproduce either sexually if there are males around, or by virgin birth if there aren’t.
For most animals, reproduction is sexual - it involves a female’s egg being fertilised by a male’s sperm. Virgin birth, or ‘parthenogenesis’, is the process by which an egg develops into an embryo without fertilisation by sperm – a male is not needed.
The offspring of a virgin birth are not exact clones of their mother but are genetically very similar, and are always female.
“We’re the first to show that you can engineer virgin births to happen in an animal – it was very exciting to see a virgin fly produce an embryo able to develop to adulthood, and then repeat the process,” said Dr Alexis Sperling, a researcher at the University of Cambridge and first author of the paper.
She added: “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.”
In the experiments, only 1-2% of the second generation of female flies with the ability for virgin birth produced offspring, and this occurred only when there were no male flies around.
When males were available, the females mated and reproduced in the normal way.
The females of some egg-laying animals – including birds, lizards and snakes, can switch naturally to give birth without males.
But virgin birth in animals that normally sexually reproduce is rare, often only observed in zoo animals, and usually happens when the female has been isolated for a long time and has little hope of finding a mate.
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