Updates from Derren Brown and the Enigma Crew

“A female boa constrictor snake has given birth to two litters of extraordinary offspring. Evidence suggests the mother snake has had multiple virgin births, producing 22 baby snakes that have no father. More than that, the genetic make-up of the baby snakes is unlike any previously recorded among vertebrates, the group which includes almost all animals with a backbone. Details are published in the Royal Society journal Biology Letters.

Virgin births do occur among animals. Many invertebrates, such as insects, can produce offspring asexually, without ever having mated. They usually do this by cloning themselves, producing genetically identical offspring. But among vertebrate animals, it remains a novelty, having been documented among less than 0.1% of vertebrate species. In 2006, scientists discovered that two komodo dragons (Varanus komodoensis), the world’s largest lizard species, had produced eggs that developed without being fertilised by sperm – a process called parthenogenesis. Then in 2007, other scientists found that captive female hammerhead sharks (Sphyrna tiburo) could also reproduce without having sex. But vertebrates generally reproduce sexually. Not including genetic material from the father – essentially having just a single biological parent – reduces genetic diversity and makes it more difficult for organisms to adapt to, for example, changed environmental conditions or the emergence of a new disease.

Now, a team of scientists and snake experts based in the US has identified the first case of a boa snake having a virgin birth. “Although parthenogenesis has been documented in a few snake species, our findings are truly novel for a number of reasons,” says Dr Warren Booth of North Carolina State University in Raleigh, US. He led the team that made the latest discovery, and also worked with the researchers who documented a virgin birth in a hammerhead shark. “The female [boa] has had not one virgin birth, but actually two, in spite of being housed with and observed to be courted by multiple males. “All offspring are female. The offspring share only half the mother’s genetic make-up,” he told the BBC. What is more, the female snake in question has produced offspring the like of which have never been seen before.

In the two years following 2007, the captive-born female Boa constrictor produced two litters of live offspring, at the same time as being housed with four male snakes. First impressions suggested there was something special about these babies: all were female and all had a particular, rare caramel colouration. This colour is a rare recessive genetic trait, which is carried by the mother but not by any of the potential fathers. So Dr Booth and colleagues conducted a series of genetic tests on the snakes to solve the enigma. What they found was astonishing. DNA fingerprinting revealed that the offspring had a number of genetic differences from any of their potential fathers, which ruled out all the males as sires of the litter. That confirmed the first instance of a known virgin birth among boa snakes.

All the offspring also had very unusual sex chromosomes. Sex chromosomes are packages of DNA that drive the development of sexual characteristics; they essentially make animals genetically male or genetically female. Humans for example have X or Y sex chromosomes; females have two X chromosomes and males have a combination of an X and a Y chromosome. In place of X and Y, snakes and many other reptiles have Z and W chromosomes. In all snakes, ZZ produces males and ZW produces females. Bizarrely, all the snakes in these litters were WW.”

Read more at BBC News (Thanks @powerofstrange)