Of dragons and microbes

[From the archives; originally posted November 22, 2005]

Carl Zimmer has a post today about the work of Dr. Bryan Grieg Fry on the evolution of snake venom. If that name sounds familiar to those of you who aren't reptile specialists, you may have run across Dr. Fry's homepage, or you may have seen his research profiled previously on Panda's Thumb here, or you may have read comments by the good doc in this thread. Zimmer, as always, has an excellent overview of Fry et al's new paper in Nature (link ), but he didn't emphasize the one sneak peek I received from Bryan.

This tasty bit of information involved monitor lizards, such as the Komodo dragon. The conventional wisdom has been that these lizards kill by infecting their prey with bactera during a bite, featured on many sites such as this one:

[The komodo dragon] can run as fast as a dog for short stretches and prey they merely injure are brought down shortly by the deadly bacteria in their mouths.

and this one:

[The komodo dragon's] saliva is not venomous, but the mouth of a Komodo dragon is so full of bacteria that a bite from one almost always leads to infection. If untreated, the infection is usually fatal.

Only thing is, it's wrong. I can't say how much bacterial infection plays a role in the killing of a komodo dragon's prey, but the research by Fry's group shows that indeed, these lizards are capable of producing venom, via previously undescribed venom glands. (Carl Zimmer has posted a figure from the Nature paper; the komodo dragon is in the Varanidae group).

Previously, it was thought that venom production in snakes and lizards had evolved independently, since the venom glands in these lineages had a different structure. However, using new DNA sequence data, Dr Fry and his colleagues found nine venom toxin types that were shared between lizards and snakes. Seven of these were previously only known from snake venoms, including one that had only previously been reported in rattlesnake venom but was sequenced by the team from the Bearded Dragon. Looks like yet another paradigm-shattering paper; y'know, the kind all the IDists say scientists are so afraid of...

Image from http://komodo.procombel.be/images/dragon.jpg