The Glade 4.0

Snake has unique 'virgin birth'
By Matt Walker
Editor, Earth News
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.

Our finding up-ends decades of scientific theory on reptile reproduction
Biologist Dr Warren Booth
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.

Novel beginnings

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.

Special babies

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.

Half clones

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.

This was further proof that the snakes inherited all their genetic material from their mother, as only females carry the W chromosome.

"Essentially they are half clones of their mother," says Dr Booth.

That is because the baby snakes have inherited two copies of one half of their mother's chromosomes, including one W chromosome.

More astonishing though, is that no vertebrate animal in which the females carry the odd sex chromosome (in this case the W chromosome) has ever been recorded naturally producing viable WW offspring via a virgin birth.

"For decades WW has been considered non-viable" says Dr Booth.

In such species, all known examples of babies born via an immaculate conception are male, carrying a ZZ chromosomal arrangement.

The only previously known animals to carry this WW chromosome pairing were created by scientists in the laboratory, using intricate genetic techniques to artificially alter the way animal eggs develop.

"Essentially our finding up-ends decades of scientific theory on reptile reproduction," says Dr Booth.

One other mystery is what prompted the female snake to give birth this way.

"This female has given birth to sexually produced babies in the past, and only in years that she was housed with males has she produced offspring," Dr Booth explains.

"It appears that some interaction with a male is required.

"However, why she does not utilise his sperm is at present unknown."

Boas snakes are kept and bred all over the world as pets.

But, Dr Booth adds, "this study tells us we have much more to learn when it comes to reproduction in these primitive reptiles".

Yeah, I saw some documentary about Burmese pythons that have been released into the Everglades. It was wild.

For some reason, I always thought that lizards produced from parthenogenesis were always female, but this article seems to imply the opposite. Am I wrong about that?

Edit: so, wikipedia has left me even more confused. There are all-female species of lizards, as I thought, but it also states that parthenogenesis produces females in XY species, and males in ZW species. I thought that all reptiles and birds were ZW...

I don't see any biological benefit to parthenogenesis producing males, so it seems odd that would be the outcome.

So, this female producing more males makes no sense.

I agree for this female it wouldn't make sense. But I thought you meant in general. I have doubts these snakes will be able to produce offspring, though. They seem pretty **** up genetically. Also, even if they could produce offspring, they would only be able to produce female offspring, right? Since they have the WW instead of the ZW?

(CNN) -- It may be an old menu standby to Vietnamese diners, but it's turned into a smorgasbord of discovery for scientists.

Researchers have identified a previously undocumented species of all-female lizard in the Mekong River delta that can reproduce itself by cloning, and the story of how it was discovered is almost as exotic as the animal itself.

Leiolepis ngovantrii is a small lizard found only in southern Vietnam. A Vietnamese reptile scientist who came across tanks full of the remarkably similar looking reptiles at small diners in rural villages in Ba Ria-Vung Tau province became intrigued when he noticed that all of the lizards appeared to be female.

So the scientist, Ngo Van Tri of the Vietnam Academy of Science and Technology, contacted an American colleague about what he was seeing. His friend -- a herpetologist at La Sierra University in Riverside, California -- immediately dropped everything to come out to assess the find.



Professor's lizard discovery in Vietnam Dr. Lee Grismer and his son, Jesse Grismer, a doctoral candidate, flew all the way to Hanoi and then faced a grueling two-day motorcycle trip out to a restaurant where the owner promised to set aside a stash of the creatures for study.

But there was a little problem, says Grismer.

"Unfortunately, the owner wound up getting drunk, and grilled them all up for his patrons... so when we got there, there was nothing left."

Another recent discovery: Red-bearded monkey

Faced with an empty tank and nearly dashed hopes, the men asked around at other cafes in the area for the local delicacy, and hired children to track down as many of the lizards as they could find.

The team soon had more than 60, and realized they had something special on their hands: a previously undocumented species.

"It's an entirely new lineage of life that was being eaten and sold in restaurants for food," says Grismer. "But it's something that scientists have missed for hundreds of years."

DNA sampling on the tiny reptiles brought another surprise: all of the lizards were female, and clones of their mothers.

It's a rare trait, but not unheard of. Some species of lizards and fish can adapt to parthenogenesis, or self-fertilization, especially when faced with adverse environments, pollution or over-hunting.

Grismer suspects that the lizards are a hybrid mix of two similar lizard species in the area, but one that is not sterile and is adapted to the increasing population of human farmers around it.

In fact, while scientists once led big expeditions to the most remote areas to find new animals, Grismer says today, that new frontier is quite often right in people's backyards.

"What we're finding is that local inhabitants know a tremendous amount about the natural histories of the regions in which they live," he says, adding that tapping into local knowledge has led to many new lizard discoveries. "It's not that they're not known... locals know all about them. It's just that they're not known to scientists."

So what does a plate full of Leiolepis ngovantrii taste like?

Well, nothing remotely like chicken, Grismer says.

"You wouldn't want to substitute it for a Big Mac or anything like that," he says, and you won't see lizard banh mi showing up on menus anytime soon.

Grismer complained that he had to hold his breath while eating the local dish to appear polite to the restaurant owners.

"You take a bite out of it and it feels like something very old and dead in your mouth," he said.