Is virgin birth just a myth? No, say scientists -- at least for the female boa constrictor, a snake species that doesn't need male support for reproduction.
This asexual reproduction, or parthenogenesis, is thought to be common among invertebrates (animals without backbones) and rare among vertebrates, but it was not known so far.
Now, for the first time, a team of researchers from the North Carolina State University at Raleigh discovered a boa constrictor that reproduces by "virgin birth".
The team, led by population and evolutionary geneticist Warren Booth, investigated a female boa constrictor at the Boa Store, an online store that sells captive-bred boa snakes in Sneedville in the US.
The female had given birth to litters of young this year and last. These offspring were all female and, unusually, were all caramel in colour like their mother.
This rare trait is recessive in nature, meaning it gets expressed only if offspring receive the DNA for it from both their parents, and none of the males that the female had been exposed to were known to carry the trait.
Genetic tests revealed that none of these litters carried any genes from any of the males their mother had known. The baby snakes must have been fatherless, said the researchers.
"It's perplexing that males were present with the female in years that she produced these parthenogenetic offspring, and in years when they were absent she did not," Booth was quoted as saying by LiveScience.
"Instances of parthenogenesis, or virgin birth, are often attributed to a lack of mates. Therefore, in cases where males are not present, the female would be better to produce parthenogenetic babies than none at all.
"Is it possible that the female selectively chose not to utilise the male sperm if breeding occurred? Is it possible that the males were genetically incompatible with the female?
We simply do not know enough about parthenogenesis in boas to speculate," Booth said.
Boas and many other creatures carry out meiosis, in which cells divide to form the respective sex cells, each of which only possess half the material needed to make offspring. For the female boa, pairs of her sex