Reptile & Amphibian Forums

Welcome to kingsnake.com's message board system. Here you may share and discuss information with others about your favorite reptile and amphibian related topics such as care and feeding, caging requirements, permits and licenses, and more. Launched in 1997, the kingsnake.com message board system is one of the oldest and largest systems on the internet.

Click for 65% off Shipping with Reptiles 2 You
Click here for Dragon Serpents

Parthenogenesis - 5 Komodo dragons born

reptayls Jan 24, 2007 05:58 PM

News article: By ROB HARRIS, Associated Press Writer
Wed Jan 24, 7:19 AM ET

MANCHESTER, England - A British zoo announced Wednesday the virgin birth of five Komodo dragons, giving scientists new hope for the captive breeding of the endangered species.

In an evolutionary twist, the newborns' eight-year-old mother Flora shocked staff at Chester Zoo in northern England when she became pregnant without ever having a male partner or even being exposed to the opposite sex.

"Flora is oblivious to the excitement she has caused but we are delighted to say she is now a mum and dad," said a delighted Kevin Buley, the zoo's curator of lower vertebrates and invertebrates.

The shells began cracking last week, after an eight-month gestation period, which culminated with the arrival on Tuesday of the fifth black and yellow colored dragon.

The dragons are between 15.5 and 17.5 inches and weigh between 3.5 and 5.3 ounces, said Buley, who leads the zoo's expert care team.

He said the reptiles are in good health and enjoying a diet of crickets and locusts.

Other reptile species reproduce asexually in a process known as parthenogenesis. But Flora's virginal conception, and that of another Komodo dragon earlier this year at the London Zoo, are the first time it has been documented in a Komodo dragon.

The evolutionary breakthrough could have far-reaching consequences for endangered species.

Captive breeding could ensure the survival of the world's largest lizards, with fewer than 4,000 Komodos left in the wild.

Scientists hope the discovery will pave the way to finding other species capable of self fertilization.

While it wasn't unusual for female dragons to lay eggs without mating, scientists understood they were witnessing something important when they realized Flora's eggs had been fertilized.

DNA paternity tests confirmed the lack of male input, although the brood are not exact clones of their mother.

Parthenogenesis — where eggs become embryos without male fertilization — had only been noted once before in a Komodo dragon. Genetic tests showed that Sungai, a resident of London Zoo, was the sole parent to offspring last April.

Replies (10)

Gophersnake13 Jan 25, 2007 06:01 AM

Neato
-----
-J.Hill

teaspoon Jan 25, 2007 09:24 AM

Awesome!
Do you know how many males and females?

craig k. Jan 26, 2007 01:30 AM

There should not be any males at all.

arpk Jan 28, 2007 11:03 AM

There can never be any male offspring if parthogenesis occurs. All offspring have to be female. There are no male genes present, no Y chromosome.

Makes you wonder about something else doesn't it?

johnscanlon Jan 28, 2007 11:19 PM

>>There can never be any male offspring if parthogenesis occurs. All offspring have to be female. There are no male genes present, no Y chromosome.
>>
>>Makes you wonder about something else doesn't it?

Wrong, actually! The real situation is surprising and interesting...

Most lizards and all snakes, like birds which evolved genetic sex-determination independently, do not have an X/Y system like us mammals (where XX is female, XY is male). Instead it's a so-called Z/W system where females, not males, are the heterogametic sex. That is, males are ZZ and females ZW. (In all of these groups there are weird lineages that have lost or duplicated one or other of the sex chromosomes, but we'll ignore those for now).

Genetic (chromosomal) sex determination seems to have evolved several times from environmebntal (usually temperature-dependent) SD as occurs in turtles, crocodilians, tuataras (Sphenodon) and some lizards (some or maybe all Iguania) usually regarded as basal, so that only a single origin of GSD is implied within Squamata. (If BGF and co. are right about 'Toxicofera' there would be at least one reversal to TSD)

The result for would-be parthenogenetic forms with Z/W GSD is that there are two viable routes: (1) by-pass meiosis (the 'reduction division' involved in producing gametes) and duplicate the genome to produce diploid eggs requiring no fertilization (thus an all-female lineage), or (2) allow one of the polar bodies (little sisters of the oocyte produced in meiosis) to re-fuse with it, producing a zygote without intervention of any foreign matter such as spermatozoa.

Varanus komodoensis has taken route (2), with the ability to fertilize its own eggs if no sperm are available, quite different from the well-known all-female parthenogens such as Cnemidophorus spp., Ramphotyphlops braminus, populations of Heteronotia binoei, and various lacertids. That's what makes this a big news story.

What happens when ZW makes gametes and fertilizes itself? You get ZZ, ZW and WW zygotes. ZZ are normal males (OK, a little inbred, but not completely homozygous at every locus). WW just doesn't work: no surviving offspring, apparently. I think I read there's some mechanism preventing daughters from developing, otherwise you'd expect twice as many as sons, but I haven't gone to the trouble of Googling for the articles I read on this just before Xmas (nor had the prior posters, obviously). You may do so now.

Cheers,
John
-----
John D. Scanlon
Riversleigh Fossil Centre
Outback at Isa
Mount Isa, Queensland, Australia
riversleigh@outbackatisa.com.au

johnscanlon Jan 28, 2007 11:23 PM

Re. my last message just posted:

>>WW just doesn't work: no surviving offspring, apparently.

Sorry Wolfgang, didn't mean to get personal.

>>Cheers,
>>John
-----
John D. Scanlon
Riversleigh Fossil Centre
Outback at Isa
Mount Isa, Queensland, Australia
riversleigh@outbackatisa.com.au

Jaykis Jan 31, 2007 01:53 PM

Was the image of Mary anywhere on the lizard? Can't wait to see the throngs leaving gifts and flowers.....
-----
1.1 Blackheaded pythons
1.0 Woma
2.1 Aussie Olives
1.1 Timors
1.1 Savu
1.1 Juvie Bloods
1.1 Juvie Balls
1.1 IJ Carpets
1.1 Coastal Carpets
1.2 Macklotts
1.1 Papuan Olives
1.0 Jungle Carpet
2.2 Scrubs (on breeding loan)
0.1 Jungle/Diamond cross
0.1 child, CB
0.1 wife, WC

CKing Mar 29, 2007 11:04 PM

>>Re. my last message just posted:
>>
>>>>WW just doesn't work: no surviving offspring, apparently.
>>
>>Sorry Wolfgang, didn't mean to get personal.
>>
>>>>Cheers,
>>>>John
>>-----
>>John D. Scanlon
>>Riversleigh Fossil Centre
>>Outback at Isa
>>Mount Isa, Queensland, Australia
>>riversleigh@outbackatisa.com.au

I think "WW" works as well in lizards as Wuster and Fry's hypothesis of a venomous common ancestry for the family Colubridae.

ramonesfan Jun 10, 2007 07:34 AM

Hmmm. I think I once read an interview with Frank Retes (I think that was his last name)...where he speculated that some Varanids may also change sex based on population dynamics...very interesting...WE DO have a lot to learn.

CKing Mar 30, 2007 01:34 AM

>>News article: By ROB HARRIS, Associated Press Writer
>>Wed Jan 24, 7:19 AM ET
>>
>>Parthenogenesis — where eggs become embryos without male fertilization — had only been noted once before in a Komodo dragon. Genetic tests showed that Sungai, a resident of London Zoo, was the sole parent to offspring last April.

Site Tools