Scientists have genetically engineered female fruit flies that have offspring without mating, the first time “virgin birth” has been induced in an animal.
The offspring of the flies were also able to give birth without mating, showing the trait can be passed down to future generations. This was revealed last week in a study in the journal Current Biology.
Virgin birth, also called parthenogenesis, is rare but not unprecedented among animals.
The females of some egg-laying animals – such as lizards and birds – are able to give birth without mating, usually late in life when no males are available.
Scientists revealed last month that a female crocodile in a Costa Rican zoo who had never been near a male laid an egg containing a fully formed fetus, the first recorded virgin birth for crocodiles.
Sexual reproduction involves a female’s egg being fertilized by sperm from a male. But in parthenogenesis, the female grows the egg into an embryo all on her own.
Alexis Sperling, a Cambridge researcher and co-author of the new study, says she was inspired to study virgin births by a pet praying mantis who produced young without any male participation.
Seeking to find a genetic cause for the phenomenon, Sperling and her colleagues decided to experiment on the fruit fly Drosophila melanogaster.
The fly, which sexually reproduces normally, is one of the most studied animals for genetic research, meaning they could take advantage of over a hundred years worth of data on the insect.
First, the researchers sequenced the genomes of two strains of another fruit fly, Drosophila mercatorum. One strain reproduces solely via virgin birth, while the other needs a male. Then, they compared the similarities and differences, to pinpoint the genes behind virgin births.
They then manipulated certain genes of the Drosophila melanogaster to match what they saw in its close relative.
The result was “fully parthenogenetic flies, which was much to my delight”, Sperling said.
The research, which spanned six years, involved over 200,000 fruit flies.
If the genetically engineered flies had access to males, they would reproduce normally.
But among those kept in isolation, 1 to 2 percent apparently gave up on ever seeing a male around halfway through their life – around 40 days – and had a virgin birth.
Their offspring – which were all female, as is the case with all virgin births – had young of their own at around the same rate.
Mammals – such as humans – are not able to have virgin births because their reproduction requires certain genes from sperm.
The recent crocodile discovery suggests that more animals are able to have virgin births than is currently known.
While virgin births are thought to be “a last-ditch effort” to keep a species going, that theory has not been proven, Sperling says.
“We can speculate that it happens later because they have given up on finding a mate – and then just put their best out there.”
