Venom Evolution

[BWSmith]

While discussing specific envenomations cases and the apparent changes in composition we are seeing, I have a thought I would like to share.

Rattlesnake venom has, in the past, generally produced hematoxic (affecting circulatory system) symptoms in the victim. All snake venom has a combination of many dofferent protiens. So there have probably always been neurotoxins present in pit viper venom. But there seems to have been a drastic shift in the composition of venom in several species of Rattlesnake. The venom seems to be losing many of its hematoxic properties and becomeing primarily neurotoxic (affecting the nervous system).

The Mojave Rattlesnake (C. scutulatus) has been known for some time to produce a very neurotoxic bite, and was thought to be the most potent venom of any rattler. There was also a recent study of the Canebrake Rattlesnake (C horridus atricaudatus) on geographic variations in thier venom composition. They found the Canebrake to have very high concentrations of neurotoxins. In fact, specimens from Lake City, FL were found to be 24% more neurotoxic than a Mojave Rattlesnake! The Eastern Diamondback Rattlesnake (C adamanteus) has also produced symptoms in its victims that indicative of a neurotoxin. The same is true for Southern Pacific Rattlesnake (C v helleri) and of course the Neotropical Rattlesnake (C durissus).

In fact, let's look at two bites from Georgia locale snakes. I will keep it short. The first, an envenomation from a neonate Canebrake. NO hematoxic effects, not even edema (swelling) or necrosis ......... nothing. But just about every common neurotoxic symptom. The second, a 3'-4' female Eastern Diamondback envenomation during a feeding response. Severe pain at the bite site and severe edema were the only hematoxic symptoms. And again, many common neurotoxic symptoms.

These two particular snakes seem to have neurotoxins as the dominant toxin in thier venom. But this is a fairly new phenomena. That is 5 species of Rattlers that I can think of off the top of my head that are producing more neurotoxins. How many more are we going to find in the next 5 years?

My point is this. These changes seem to be occuring at an amazing rate. Typically, we think of evolution and survival of the fittest procucing such changes. Those animals most fit to survive are going to breed and new offspring carrying those advanced traits are produced. okay. The speed at which this change seems to be occuring is too rapid for simply selective breeding. I submit that the venom is not so much evolving through generations, but in the snake itself. I believe that venom is not a stationary substance, like for example a can of coke. Think of the snake as a case of coke. And the cans as doses of venom. What is commonly held at this time is that each can of coke is going to be chemically the same when opened. I believe that the chemical composition can change depending on the environment. I am not saying it sees a human and switches to Neurotoxin Mode. But I don't think that the speed of these changes and the geographic diversity lend themselves to traditional explinations.

This is pretty much rambling without having finished my first cup of coffee.