Rethinking snake & lizard venoms....

[Dr Mordrid]

Interesting article;

http://www.livescience.com/animalworld/051117_lizard_venom.html

Scientists used to believe that snakes evolved venom between 60 million and 80 million years ago. Lizards were said to have developed it around 100 million years ago, independent of their legless cousins.

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.

Iguanas stuck with the primitive configuration – glands on the top and bottom – but other lizards, like the Gila monster and the Komodo dragon, developed glands only on their lower jaw.

"They're like two pieces of macaroni on either side of the jaw with hoses leading to the teeth," Fry said.

Bacteria has long been blamed as the aggravating agent in a Komodo dragon's nasty bite. Fry now suspects otherwise.

"Bacteria couldn't work this quickly," he said. "The effects are totally inconsistent with bacteria."

Dr. Mordrid

[Brian Ellis]

I suspect that venom is probably a lot older than vertebrates. If we take an ordinary spider, for example, when it bites its prey, the inside of the exoskeleton is predigested to an almost liquid form. This suggests to me that venom possibly developed from the enzymes in saliva used to aid in the preliminary stages of food digestion. If so, all animals are, in some degree, venomous to at least some other species, even us. Our "venom" is obviously very mild because we have not evolved to use it as a weapon or for defence, and we do not have the means of using it for either. If you have a stringy piece of meat stuck hard in the teeth without the means of dislodging it, it will soften in a few hours so that it will eventually drop out. This is because of enzymatic digestion. Aphthous ulcers in the mouth are the result of damage to the mucous membrane, allowing digestion of one's own tissue until the membrane is restored. Untreated major dog bites may exhibit decomposition of the tissue, consistent with enzyme action (sometimes even leading to gangrene). Lions will follow prey that they have bitten but have managed to escape without serious injury, knowing that they will collapse in a few hours.

Of course, snakes have perfected the technique as both defence and offence measures, along with spiders and scorpions to a somewhat lesser extent. Among mammals, the duck-billed platypus has adapted its rear hang-claws into a venomous spur (for defence????).