Saturday, November 19, 2005
Now That's Toxic!
I retain my boyish fascination with all things reptilian and venomous. (Remind me to tell you the story about the time I brought a water moccasin home from my grandfather's farm sometime.) Thus I read these two article with relish.
They are the same story, told quite differently, about how a researcher in Australia has found that many of the common lizard varieties found there in fact carry venom. The explanation is that rather than inject large quantities of venom like a snake, the mix it in their mouths with saliva, thus significantly diluting it and making it not terribly harmful to humans.
They have also used the research to change the entire evolutionary model of reptilian development.
I think the fact that lizards have venom is cool, but I have a lot of questions.
Firstly, why did it take this long to find this out. It's not like these lizards haven't been studied to death. As a kid I did more than my share of amateurish garage dissections of lizards I caught in the yard, and I was always running around with some bloody little vesicle I found in the things head trying to find out if it was venomous. I know that makes me a little weird, but I have to think I wasn't the only one. One of us should have grown up and followed up on that a long time ago.
The other thing relates to the evolutionary conclusions they draw. From the LiveScience piece.
Just shows there is a world of difference, between an explanation that fits the data and data actually supporting a theory.
The Surprising Origin of Venom Revealed - LiveScience.com
Australia's lizards are venomous too - ABCNews
Australia's lizards are venomous too - ABCNews
They are the same story, told quite differently, about how a researcher in Australia has found that many of the common lizard varieties found there in fact carry venom. The explanation is that rather than inject large quantities of venom like a snake, the mix it in their mouths with saliva, thus significantly diluting it and making it not terribly harmful to humans.
They have also used the research to change the entire evolutionary model of reptilian development.
I think the fact that lizards have venom is cool, but I have a lot of questions.
Firstly, why did it take this long to find this out. It's not like these lizards haven't been studied to death. As a kid I did more than my share of amateurish garage dissections of lizards I caught in the yard, and I was always running around with some bloody little vesicle I found in the things head trying to find out if it was venomous. I know that makes me a little weird, but I have to think I wasn't the only one. One of us should have grown up and followed up on that a long time ago.
The other thing relates to the evolutionary conclusions they draw. From the LiveScience piece.
But after comparing the genetic code for snake and lizard venom, Bryan Fry at the University of Melbourne, Australia discovered that the two reptiles shared nine toxins. This supports the idea that snakes and venomous lizards evolved from a common venomous ancestor, and after connecting the DNA dots, Fry and his colleagues traced venom to a single origin 200 million years ago.That's an awful lot of conclusion from not a whole lot of data. Might a fossil of that common ancestor be helpful? How do they know about the jaw thing, just because there are breeds with either/or so the common ancestor must have had both? I know we don't understand the genetic code that well. This rises to the level of presumption, not conclusion. It may fit the available data, but when you have such sparse data, I would be careful how I presented something like that.
"That's also when the small, bite-sized animals were starting to exist. Any time there's a new food source you see the emergence of a new predatory trick," Fry told LiveScience. "In this case, venom was the new trick."
The common ancestor had venom glands on both its upper and lower jaws. Since then, snakes have evolved to having glands on just their upper jaw; glands on the lower would make it difficult to swallow prey.
Just shows there is a world of difference, between an explanation that fits the data and data actually supporting a theory.
