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Venom discovery leads to reptile revolution |
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Research by an Aussie lizard lover has uncovered venomous evidence that is going to rewrite the history of reptile evolution.
The new discovery has found that goannas and iguanas are venomous, and share a common venomous ancestor with snakes.
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As deputy director of the Australian Venom Research Unit, Bryan's childhood dream of playing with venomous animals for a living has come true
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Based at the Australian Venom Research Unit, Dr Bryan Fry led a team of 14 researchers spread over six countries. Their findings describe the existence of oral venom glands in goannas and iguanas. The discovery already has herpetologists reaching for their reptile family trees - because it proves that venom systems in snakes and lizards evolved before, not after, the two species started their shuffle down different evolutionary paths.
Bryan explained the new insights into venom system evolution mark a major shift in the understanding of reptile evolution, and could even lead to the development of new drugs.
"It not only has profound theoretical implications, but also has enormous potential for drug design and development," he said. "This is because the venoms have been separated for up to 200 million years from anything previously studied."
Prior to the team's findings, scientists believed that venom systems appeared relatively late in evolution and were limited to the 'front-fanged' snakes, such as cobras, rattlesnakes and sea snakes.
Bryan is no stranger to toppling established theories, with earlier work showing that venom systems were a shared trait of all advanced snakes, not just ones with their pearly whites up front.
From their names, you can imagine that the Gila monster and Mexican bearded lizard are two fellows you wouldn't want to meet in a dark alley. Until now, these species had the exclusive position of being the only lizards known to have venom systems. Because their venom glands had a different structure than those of their snakey counterparts, everyone assumed that the venom systems had evolved independently.
If you have ever been confronted by a human with breath bad enough to knock you out, spare a thought for monitor lizards like the Komodo Dragon. Everyone thought that it was toxic bacteria in their mouth that gave them the ability to kill prey.
Using new DNA sequence data, Bryan's team have now cleared the names (and breath) of monitor lizards everywhere. But the revelation that venom, not bacteria, is their hunting secret won't please everyone, especially over-anxious mums.
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Bryan with another snakey friend - a king cobra
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The team found that nine toxic venom types were shared between lizards and snakes, seven of which were previously only known from snake venoms. And boosting the reputation of popular pet the Bearded Dragon, these little lizards were found to have toxins that had previously only been reported in rattlesnake venoms!
"The elation I felt is beyond description," smiled Bryan. "It is the best high out there."
So now that we know that all snake and lizard species that possess toxin-secreting oral glands come from a single common ancestor, does that mean lizards should gain the same fearful reputation as snakes?
Bryan explained that like many snakes, the venomous lizards did not evolve hollow fangs. Instead, hanging onto the poison in their saliva, they have to rely on making deep punctures to make sure that a bit of venom goes into the wound.
"The venom is working in concert with very big teeth," Bryan explained. "If you have a wound deep enough to cause considerable bleeding, the venom will prolong this and exacerbate the effect."
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