Reptile Forum, Reptile Classifieds - CaptiveBred

[Eddie]

I found this article in this weeks New Scientist Magazine and thought it makes some interesting reading. I scanned the page but was unable to attach it, so I have just copied the text.

101 New/Scientist 119 November 2005

The pet shop never mentioned venom
EMMA YOUNG, SYDNEY

PEOPLE bitten by their pet lizard can suffer a painful swelling and prolonged bleeding. Infection by bacteria in the lizard's mouth was always assumed to be the cause, but it turns out that many lizards, including some that are common pets, are actually venomous. The finding is rewriting the evolutionary family tree of lizards and snakes.
"To find the classic rattlesnake toxins in the bearded dragon -
hugely popular pet - was a huge surprise," says Bryan Fry at the University of Melbourne, Australia, who led the work.

Venom was considered the preserve of advanced snakes and just two species of lizard, the gila monster (Heloderma suspectum) and the Mexican beaded lizard (Heloderma horridum). It was thought that these lizards evolved the ability to produce venom independently of the snakes.
Now Fry's team has found that two other groups, the monitor lizards and iguanians, which includes iguanas and chameleons, are also venomous. They share nine of the toxins produced by snakes, but make others that have not been identified before (Nature, DOI: I0.l038/nature04328).
In a related paper published in the journal Comptes Rendus Biologies this week, Nicolas Vidal and Blair Hedges of Pennsylvania State University in University Park, two of Fry's co-authors, dub this new family of toxic reptiles Toxicofera.

And they suggest a complete overhaul of the whole classification system is needed. "These papers threaten to radically change our concepts of lizard and snake evolution, and particularly of venom evolution," says Harry Greene, a herpetologist at Cornell University in New York.
DNA analysis by Vidal and Hedges suggests that the closest relatives of snakes are iguanians, of which there are about 1440 species, and anguimorphs, a group that includes the two lizard species already known to be venomous, and monitor lizards. This means iguanas and their close relatives probably evolved much later than was previously thought and suggests that venomous lizards and snakes are descended from a common ancestor that lived around 200 million years ago. This pushes back the evolution of venom by 100 million years, coinciding with the rapid spread of small mammals.

The paper also suggests that the method of classifying reptiles that has been used for the past 80 years, which is based partly on the texture of the tongue, should be changed. It is an unreliable method for inferring evolutionary relationships, "To find the classic rattlesnake toxins in the bearded dragon, a hugely popular pet, was a huge surprise"
Hedges says. Characteristics such as venom production and egg teeth, which hatchlings use to escape from their egg, are more useful, he says.
But how could venom production in these lizards have been overlooked for so long? Fry suggests that blaming bacteria had become dogma. Komodo dragons, for example, are monitor lizards that eat carrion, and their mouths are blooming with bacteria. "It was the classic red herring," he says. Also, while the toxins produced by these lizards might kill their usual prey, they have less potent and so less noticeable effects on people.

[Jamesg]

Just to follow that for anyone interested

Venom research bad-mouths goannas

By Deborah Smith, Science Editor
November 18, 2005

A toxic shock ... a desert spotted goanna, like all goannas, has poison glands in its jaws. Alexia Fry

The secret behind the nasty bite of goannas has been revealed.

The lizards are more closely related to snakes than previously thought and produce a similar venom, researchers have found.

Bryan Fry, of the Australian Venom Research Unit at the University of Melbourne, said his team's surprise discovery could lead to the development of new medicines based on lizard toxins.

"These molecules represent a tremendous, hitherto unexplored resource for utilisation in drug design," he said.

Goannas are monitor lizards, a group which includes the Komodo dragon.

Dr Fry said that because these carnivores fed on carrion in the wild, toxic bacteria in their mouths had long been blamed for the pain, swelling and prolonged bleeding caused by bites.

His suspicions were alerted, however, when he saw a zookeeper in Singapore develop symptoms rapidly after being bitten by a captive Komodo dragon which had been brought up on fresh food.

"It didn't sit right with me; bacteria don't work that fast," Dr Fry said.

When he studied an Australian lace monitor, or common goanna, the closest living relative of a Komodo dragon, he found a huge gland running down the side of its jaw. Squeezing it released the venom.

"You could see it pooling at the base of the teeth. It's amazing what you find when you look."

His international team, which includes researchers from Monash University, has identified nine types of toxins from lizard venom which snakes also produce. One toxin found in the venom of the bearded dragon, one of the most popular pet lizards in the world, had previously been identified only in rattlesnake venom.

However, Dr Fry said goanna lovers need not be alarmed, because the venom in these lizards was not present in amounts large enough to cause serious harm. Unlike snakes, lizards do not have fangs to inject venom into their prey.

The research, which is published today in the journal Nature, suggests venom systems in reptiles evolved only once, and much earlier than had been thought - about 200 million years ago - in a common ancestor of snakes and lizards.

The team also found iguanas produced venom. Before the study, only two species of lizards from North America, the Gila monster and the Mexican beaded lizard, were known to produce venom and it had been thought they evolved this ability independently of snakes.

Dr Fry, who has previously worked with highly venomous snakes, said he enjoyed being able to relax while studying goannas. "They're beautiful animals," he said.

Last week he was awarded a $145,000 Australian Research Council grant to study lizard venom. Venom from lace monitors has already been found to have a strong effect on blood pressure and blood clotting.
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3.7.3 Stuff!

[Muttley_109]

has anyone read/heard anymore on this subject??

[cass]

yes its been around a while this statement and has been changed , cut and copied that many times its become like Chinese whispers , so i would just ignore it , the only thing close to it is the Mexican bearded dragon from Mexico , the bds we keep as pets are from Australia , the Mexican bd is ment to be venomous but i dont know any 1 who keeps them or knows anything abut them , I also know a lot of people who have been bitten by bds and there all fine so nothing to worry about ,,
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http://www.beardieboard.com/

[Muttley_109]

lol Im not worried about it Im just interested.
I wanted to know if theres was any truth in it.

[Mememe]

It is true
While they are 'venomous', they wouldn't harm a human.
If bitten by a lizard, I would be more worried aboutit getting infected.

"However, Dr Fry said goanna lovers need not be alarmed, because the venom in these lizards was not present in amounts large enough to cause serious harm. Unlike snakes, lizards do not have fangs to inject venom into their prey. "

What it does tell us is something perhaps about the evolution of venomous snakes.

The Gila monster and Beaded lizard were thought to be the only venomous lizards, and I still consider them to be the only 'active' envenomating lizards - chewing venom into the bite wound.


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No man is an Island. Except the Isle of Man.

[Muttley_109]

so what about komodos then? Have they decided if it is the bacteria or venom?

[Mememe]

Both, I think.
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No man is an Island. Except the Isle of Man.

[cass]

sorry my mistake , there is no such thing as a mexican bearded dragon it is a ,,, mexican bearded lizard or as we on this forum know them as gila monsters , sorry for giving out false info there
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[Muttley_109]

I thought the mexican beaded lizard and gila monster were 2 seperate lizards, both venomous