Rapid venom evolution in pit vipers may be defensive

Jul 18, 2011

Research published recently in PLoS One delivers new insight about rapid toxin evolution in venomous snakes: pitvipers such as rattlesnakes may be engaged in an arms race with opossums, a group of snake-eating American marsupials. Although some mammals have long been known to eat venomous snakes, this fact has not been factored into previous explanations for the rapid evolution of snake venom. Instead, snake venom is usually seen as a feeding, or trophic, adaptation. But new molecular research on snake-eating opossums by researchers affiliated with the American Museum of Natural History suggests that predators factor into the rapid evolution of snake venom.

"Snake venom toxins evolve incredibly rapidly," says Robert Voss, curator in the Department of Mammalogy at the American Museum of Natural History. "Most herpetologists interpret this as evidence that venom in snakes evolves because of interactions with their prey, but if that were true you would see equally rapid evolution in toxin-targeted molecules of prey species, which has not yet been seen. What we've found is that a venom-targeted protein is evolving rapidly in mammals that eat snakes. That suggests that venom has a defensive as well as a trophic role."

Several groups of mammals are known for their ability to eat venomous snakes, including hedgehogs, mongooses, and some . Opossums, which belong to the marsupial family Didelphidae, consist of about one hundred known and several dozen undescribed species. Most of these opossums live in Central and South America, although there is one representative in the north that is familiar to those who spend time outside at night: the Virginia opossum.

Some didelphids, including the Virginia opossum, are known to eat rattlesnakes, copperheads, and some species of tropical pitvipers known as lanceheads. All of these pitvipers have venom containing dozens of highly , including many that attack , causing massive internal hemorrhaging in nonresistant warm-blooded , mainly rodents and birds.

The new research came out of a previous phylogenetic study of , published as a Bulletin of the American Museum of Natural History, that suggested unusually rapid evolution in one gene among a group of snake-eating opossums. The rapidly evolving gene codes for von Willebrand's factor, an important blood-clotting protein that is known to be the target of several toxins. The association of in a venom-targeted gene among just those opossums known to eat pitvipers was the essential clue that prompted further study.

"This finding took us by surprise," says Sharon Jansa, associate professor in the Department of Ecology, Evolution and Behavior at the University of Minnesota and a Museum research associate. "We sequenced several genes—including the one that codes for von Willebrand Factor (vWF)—to use in a study of opossum phylogeny. Once we started to analyze the data, vWF was a real outlier. It was evolving much more rapidly than expected in a group of opossums that also, as it turns out, are resistant to pitviper venom."

The recently published research demonstrates that the rate of replacement substitutions (nucleotide changes that result in amino-acid changes) is much higher than the rate of silent substitutions (nucleotide changes that have no effect on the protein) in the von Willebrand Factor gene among pitviper-eating opossums. Typically, high rates of replacement substitutions means that the gene is under strong, sustained natural selection. That only happens in a few evolutionary circumstances.

"Most nucleotide substitutions have little or no effect on protein function, but that doesn't seem to be the case with vWF in these venom-resistant opossums," says Jansa. "The specific amino acids in vWF that interact with toxin proteins show unexpectedly high rates of replacement substitutions. These substitutions undoubtedly affect protein function, suggesting that the vWF protein can no longer be attacked by these snake toxins."

"It is so uncommon to find genes under strong positive selection, that the exceptions are really interesting and often conform to one evolutionary circumstance when two organisms are coevolving with each other," says Voss. "We've known for years that venom genes evolve rapidly in snakes, but the partner in this arms race was unknown until now. Opossums eat snakes because they can."

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Provided by American Museum of Natural History

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flicktheswitch
5 / 5 (3) Jul 18, 2011
In before intelligent design!
Not that we'll see KevinRTS on this one... too much evidence for evolution works the same way as garlic and sunshine...
Telekinetic
1 / 5 (6) Jul 18, 2011
How many generations of snakes does it take so that the "naturally selected" or surviving snakes' venom is effective again to kill their enemies? I doubt that's really the way a rapidly-changing venom is created. And I don't mean the "Creator" either. I have a suspicion that we know too little about the consciousness of animals, by the fact of how little we know about our own. I'm suggesting that animals , by way of consciousness, can alter and shape their physical needs over a much shorter time than has previously been thought. These changes aren't consciously made, but I've always thought that DNA itself has consciousness that can affect changes required for survival, the most powerful force of life.
Y8Q412VBZP21010
3.2 / 5 (5) Jul 18, 2011
I'm suggesting that animals , by way of consciousness, can alter and shape their physical needs over a much shorter time than has previously been thought. These changes aren't consciously made, but I've always thought that DNA itself has consciousness that can affect changes required for survival, the most powerful force of life.


I am visualizing Lamarck in some other world ... I'm not sure if he's happy to realize that people are still hanging on to his ideas after all these centuries, or in despair over the fact that in all that
time nobody's come up with a better argument for them.
FrankHerbert
0.7 / 5 (49) Jul 18, 2011
Ugg, I gave Y8Q412VBZP21010 a 5 but then I almost immediately realized that his comment was most likely a dog-whistle criticism of evolution.

The random-string-of-characters username, 2 day old regdate, and only having posted in this topic kind of give it away.
Telekinetic
2 / 5 (8) Jul 18, 2011
I wouldn't apply Lamarck's theory to my own, because there is a difference. He proposed that animals can change themselves like the giraffe's long neck by its constant stretching. I'm talking about a much more subtle force, that from a mechanistic scientist's perspective, can't acknowledge lest they be ostracized from their community of mechanistic colleagues. That kind of peer pressure can alter your experience despite what you see with your own two eyes. I've seen it happen many times, and it's the kind of denial that is impossible to overcome. There are forces at work in the life of a cell that are unfolding before our eyes, astounding and never-before-imagined. We have a very long way to go before knowing all of life's processes. A virus will inject its DNA into a cell to convert it to one of its own, isn't that beyond the action of just a dumb collection of nucleic material? Or the way a virus can lay low and reappear years later?

Telekinetic
1.8 / 5 (5) Jul 19, 2011
Scoff if you'd like, but the mind/body connection is undeniable and reams of new, valid information have been compiled in the past couple of decades. If brain signaling, a multi-tasking, highly sophisticated mechanism used by an organism to heal itself, trigger specific muscles, control involuntary functions, and so on, why couldn't it also signal and communicate with its own DNA,a soldier in the offensive/defensive strategies of survival?
antialias_physorg
3.7 / 5 (3) Jul 19, 2011
why couldn't it also signal and communicate with its own DNA,a soldier in the offensive/defensive strategies of survival?

[sarcasm mode on]
Yes, and the mind certainly can control quantum states of individual atoms in your body.
[sarcasm mode off]

You have to take into account what the mind can do via electric impulses viz: Control over muscles, senory apparatus and glands (i.e. anything that is enervated via nerve cells).
DNA does not fit that bill.

Telekinetic
1.8 / 5 (5) Jul 19, 2011
DNA certainly does fit the bill. Its ability to monitor its own accuracy, snip out mutations, and replace defective sections with exact matches of the original in repair mode billions of times a minute in the body is awe-inspiring. You think an organism is just a jumble of electrical connections that act like a man-made device? That device would take eons to build.
Y8Q412VBZP21010
3 / 5 (2) Jul 19, 2011
Ugg, I gave Y8Q412VBZP21010 a 5 but then I almost immediately realized that his comment was most likely a dog-whistle criticism of evolution.

The random-string-of-characters username, 2 day old regdate, and only having posted in this topic kind of give it away.


FH, you're trying too hard. TK's pseudo-Lamarckian ideas predate modern evo science, no matter how hard TK tries to dress them up in whizzy bafflegab.

In a previous existence, I suggested I was serving a useful purpose by providing opportunities to those who like to argue over slender pretexts. I am pleased to see I am doing the same in my new existence.
antialias_physorg
5 / 5 (3) Jul 19, 2011
The point was: How do neural impulses from the mind act on DNA?
The DNA trepair mechanism is one (of many) autonomous mechnaisms working in the body (e.g. our immune system or the system that keeps our pH balance within acceptable limits)

Scoff if you'd like

Consider yourself scoffed.
Y8Q412VBZP21010
1 / 5 (1) Jul 19, 2011
Scoff if you'd like, but the mind/body connection is undeniable and reams of new, valid information have been compiled in the past couple of decades. If brain signaling, a multi-tasking, highly sophisticated mechanism used by an organism to heal itself, trigger specific muscles, control involuntary functions, and so on, why couldn't it also signal and communicate with its own DNA,a soldier in the offensive/defensive strategies of survival?


Have you talked to Deepak Chopra about this? I am sure he would be fascinated. But no doubt he would suggest adding in comments about quantum physics, too.

I am not ruling out that TK is taking the mickey. But that would make talking to Deepak C even more fun.
Y8Q412VBZP21010
1 / 5 (1) Jul 19, 2011
Consider yourself scoffed.


"When you're out of scoff ... you're out of jeer."
Telekinetic
1 / 5 (2) Jul 19, 2011
@Y8Q412VBZP21010:
You remind me of a boy in an English boarding school, "mum doesn't come around very much"; smart and lonely. You don't make any real rebuttal, you just snipe and expect to hide behind the backs of others who share your predispositions.Make a scientific-based argument that disproves my assertions.
Y8Q412VBZP21010
3 / 5 (2) Jul 19, 2011
Make a scientific-based argument that disproves my assertions.


Eh? I was half-thinking you were joking. I found it hard to believe you were serious.

But it seems you aren't. If you're challenging me to give you a clue, I concede defeat as fast as I possibly can: "MISSION IMPOSSIBLE!"

If you do want to get refutations, I suggest you offer a $10,000 prize to anyone who can convince you that you're wrong. Admittedly, anyone with sense knows that really means: "I'll give away $10,000 before I'll admit that I'm wrong." Offer as big a prize as you like, your money is safe.
Telekinetic
2 / 5 (4) Jul 19, 2011
Make a scientific-based argument that disproves my assertions.


Eh? I was half-thinking you were joking. I found it hard to believe you were serious.

But it seems you aren't. If you're challenging me to give you a clue, I concede defeat as fast as I possibly can: "MISSION IMPOSSIBLE!"

If you do want to get refutations, I suggest you offer a $10,000 prize to anyone who can convince you that you're wrong. Admittedly, anyone with sense knows that really means: "I'll give away $10,000 before I'll admit that I'm wrong." Offer as big a prize as you like, your money is safe.

Another thing that I'm right about is that your histrionics are a weak attempt to weasel your way out of a direct challenge. You have nothing at all to say.
Y8Q412VBZP21010
not rated yet Jul 19, 2011
You have nothing at all to say.


Oh, I never thought it was much, I was just being silly. But the difference between you and me is that I'm silly on purpose.

Bored now. THE END.
Deesky
4 / 5 (4) Jul 19, 2011
Another thing that I'm right about is that your histrionics are a weak attempt to weasel your way out of a direct challenge. You have nothing at all to say.

Yes, but he said it in such an eloquently whimsical way, you gotta give him props.
Telekinetic
2 / 5 (3) Jul 20, 2011
You think that's eloquence, Deesky? His last post is a child overturning a game board when he knows he's losing.
Deesky
5 / 5 (2) Jul 20, 2011
You think that's eloquence, Deesky?

Sorry, but yes, I do.

His last post is a child overturning a game board when he knows he's losing.

Not really. He's pretty much stated his case and signed off.
Telekinetic
1 / 5 (1) Jul 20, 2011

"Not really. He's pretty much stated his case and signed off."
- in a huff.
CarolinaScotsman
3 / 5 (2) Jul 24, 2011
opossums, a group of snake-eating American marsupials

So, 'possums are good for something besides speed bumps.
Y8Q412VBZP21010
5 / 5 (1) Jul 24, 2011
opossums, a group of snake-eating American marsupials

So, 'possums are good for something besides speed bumps.


"Why did the chicken cross the road?"

"To show the possum it could be done."
Ethelred
1 / 5 (1) Jul 30, 2011
Make a scientific-based argument that disproves my assertions.
There is no such biological mechanism. Such a mechanism would require an instinctive knowledge of each and every codon in the DNA and how they interact to produce the phenotype.

Now there IS a mechanism for increasing the rate of mutation but there is no way to controll where the mutations occur. When an organism is under stress it produces various chemicals that can increase mutation rates. Mutations are random and not directed. The direction of evolution comes from the environment not some magical knowledge of how all the chemicals interact.

Another thing that I'm right about is that your histrionics are a weak attempt to weasel your way out of a direct challenge. You have nothing at all to say.
Now that one you got right. He seems to be an evader.

Ethelred
Ethelred
1 / 5 (1) Jul 30, 2011
Now that one you got right. He seems to be an evader.
Then again maybe he has just gotten a bit tired and waspish.

http://gvgpd.prob...read=631

I am pretty he is the Administrator on that thread.

Ethelred
Y8Q412VBZP21010
not rated yet Jul 30, 2011
Then again maybe he has just gotten a bit tired and waspish.


Tired yes, waspish no. I have well learned not to rise to the bait any longer when a troll demands that I "refute his claims" ... that is, give him a clue.

"I'm sorry Dave, I can't do that." If I have a serious argument to make, I'm going to make it in a serious fashion and not in weary online exchanges with people who are playing the clown.

Mind you, I'm perfectly willing to play the clown if it amuses me, but when I do so it is very much on purpose.