w***@yahoo.com
2006-12-20 21:51:35 UTC
Sun 8 Jul 2001 17:47
'Virgin births' for giant lizards
A parthenogenic Komodo dragon hatching from its egg (Ian Stephen)
There have been two reported cases of Komodo dragon "virgin births"
The largest lizards in the world are capable of "virgin births".
Scientists report of two cases where female Komodo dragons have
produced offspring without male contact.
Tests revealed their eggs had developed without being fertilised by
sperm - a process called parthenogenesis, the team wrote in the journal
Nature.
One of the reptiles, Flora, a resident of Chester Zoo in the UK, is
awaiting her clutch of eight eggs to hatch, with a due-date estimated
around Christmas.
Kevin Buley, a curator at Chester Zoo and a co-author on the paper,
said: "Flora laid her eggs at the end of May and, given the incubation
period of between seven and nine months, it is possible they could
hatch around Christmas - which for a 'virgin birth' would finish the
story off nicely.
"We will be on the look-out for shepherds, wise men and an unusually
bright star in the sky over Chester Zoo."
Flora, who has never been kept with a male Komodo dragon, produced 11
eggs earlier this year. Three died off, providing the material needed
for genetic tests.
Flora the Komodo dragon (Chester Zoo archives)
Flora had never been kept with male Komodo dragons
These revealed the offspring were not exact genetic copies (clones) of
their mother, but their genetic make-up was derived just from her.
The team concluded they were a result of asexual reproduction, and are
waiting for the remaining eight eggs to hatch.
Abnormal phenomenon?
Another captive-bred female called Sungai, at London Zoo in the UK,
produced four offspring earlier this year - more than two years after
her last contact with a male, the scientists reported in the same
paper.
Again, genetic tests revealed the Komodo dragon babies, which are
healthy and growing normally, were produced through parthenogenesis.
Sungai was also able to reproduce sexually, producing another baby
offspring after mating with a male called Raja.
Maybe parthenogenesis is much more widespread and common than
previously considered
Richard Gibson
Richard Gibson, an author on the paper and a curator at the Zoological
Society of London, said: "Parthenogenesis has been described before in
about 70 species of vertebrates, but it has always been regarded to be
a very unusual, perhaps abnormal phenomenon."
It has been shown in some snakes, fish, a monitor lizard and even a
turkey, he said.
"But we have seen this in two separate, unrelated female Komodo dragons
within a year, so this suggests maybe parthenogenesis is much more
widespread and common than previously considered."
He added: "Because these animals were in captivity for years without
male access, they reproduced parthenogenetically.
Komodo dragon born to Sungai (Daniel Sprawson/ZSL)
Sungai's offspring are doing well
"But the ability to reproduce parthenogenetically is obviously an
ancestral capability."
He said the lizards could have evolved the ability to reproduce
asexually when, for example, a lone female was washed up alone on an
island with no males to breed with.
Because of the genetics of this process, he added, her children would
always be male. And like Sungai, she would be able to switch back to
sexual reproduction, so she could breed to establish a new colony.
There are fewer than 4,000 Komodo dragons in the wild, and they are
found in three islands in Indonesia: Komodo, Flores and Rinca.
Adult males can grow up to 3m (10ft) in length and weigh up to 90kg
(200lb) - making them the biggest lizards on the planet.
The researchers said that, to ensure genetic diversity of Komodo
dragons kept in captivity, zoos should perhaps keep males and females
together to avoid asexual reproduction.
I like the idea that the bigger the hive the smarter the individual.
It brings me to the question I posted some years ago and received many a
flame for. In Alien, Ridley Scott's vision of the life cycle was to have the
prey eventually become the egg, thereby continuing the cycle. But he cut
that out for time and pacing reasons. I asked if they should restore that
scene for the 20th anniversary. Many people took personal affront to this
stating that it would negate the whole hive theme/ mother/queen in Aliens.
I argued back that in the hive the queen does the breeding the warriors do
the protecting, but because this is an "alien" species who knows what they
will do to continue their life when faced with isolation? Who says that a
lone alien can't make an egg, albeit slowly.
Any thoughts?
My two pennies
Rob
http://news.bbc.co.uk/1/hi/sci/tech/6196225.stmIt brings me to the question I posted some years ago and received many a
flame for. In Alien, Ridley Scott's vision of the life cycle was to have the
prey eventually become the egg, thereby continuing the cycle. But he cut
that out for time and pacing reasons. I asked if they should restore that
scene for the 20th anniversary. Many people took personal affront to this
stating that it would negate the whole hive theme/ mother/queen in Aliens.
I argued back that in the hive the queen does the breeding the warriors do
the protecting, but because this is an "alien" species who knows what they
will do to continue their life when faced with isolation? Who says that a
lone alien can't make an egg, albeit slowly.
Any thoughts?
My two pennies
Rob
'Virgin births' for giant lizards
A parthenogenic Komodo dragon hatching from its egg (Ian Stephen)
There have been two reported cases of Komodo dragon "virgin births"
The largest lizards in the world are capable of "virgin births".
Scientists report of two cases where female Komodo dragons have
produced offspring without male contact.
Tests revealed their eggs had developed without being fertilised by
sperm - a process called parthenogenesis, the team wrote in the journal
Nature.
One of the reptiles, Flora, a resident of Chester Zoo in the UK, is
awaiting her clutch of eight eggs to hatch, with a due-date estimated
around Christmas.
Kevin Buley, a curator at Chester Zoo and a co-author on the paper,
said: "Flora laid her eggs at the end of May and, given the incubation
period of between seven and nine months, it is possible they could
hatch around Christmas - which for a 'virgin birth' would finish the
story off nicely.
"We will be on the look-out for shepherds, wise men and an unusually
bright star in the sky over Chester Zoo."
Flora, who has never been kept with a male Komodo dragon, produced 11
eggs earlier this year. Three died off, providing the material needed
for genetic tests.
Flora the Komodo dragon (Chester Zoo archives)
Flora had never been kept with male Komodo dragons
These revealed the offspring were not exact genetic copies (clones) of
their mother, but their genetic make-up was derived just from her.
The team concluded they were a result of asexual reproduction, and are
waiting for the remaining eight eggs to hatch.
Abnormal phenomenon?
Another captive-bred female called Sungai, at London Zoo in the UK,
produced four offspring earlier this year - more than two years after
her last contact with a male, the scientists reported in the same
paper.
Again, genetic tests revealed the Komodo dragon babies, which are
healthy and growing normally, were produced through parthenogenesis.
Sungai was also able to reproduce sexually, producing another baby
offspring after mating with a male called Raja.
Maybe parthenogenesis is much more widespread and common than
previously considered
Richard Gibson
Richard Gibson, an author on the paper and a curator at the Zoological
Society of London, said: "Parthenogenesis has been described before in
about 70 species of vertebrates, but it has always been regarded to be
a very unusual, perhaps abnormal phenomenon."
It has been shown in some snakes, fish, a monitor lizard and even a
turkey, he said.
"But we have seen this in two separate, unrelated female Komodo dragons
within a year, so this suggests maybe parthenogenesis is much more
widespread and common than previously considered."
He added: "Because these animals were in captivity for years without
male access, they reproduced parthenogenetically.
Komodo dragon born to Sungai (Daniel Sprawson/ZSL)
Sungai's offspring are doing well
"But the ability to reproduce parthenogenetically is obviously an
ancestral capability."
He said the lizards could have evolved the ability to reproduce
asexually when, for example, a lone female was washed up alone on an
island with no males to breed with.
Because of the genetics of this process, he added, her children would
always be male. And like Sungai, she would be able to switch back to
sexual reproduction, so she could breed to establish a new colony.
There are fewer than 4,000 Komodo dragons in the wild, and they are
found in three islands in Indonesia: Komodo, Flores and Rinca.
Adult males can grow up to 3m (10ft) in length and weigh up to 90kg
(200lb) - making them the biggest lizards on the planet.
The researchers said that, to ensure genetic diversity of Komodo
dragons kept in captivity, zoos should perhaps keep males and females
together to avoid asexual reproduction.