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At Phys.org: To keep up with evolving prey, rattlesnakes tap genetically diverse venom toolbox


In the evolutionary arms race between rattlesnakes and their prey, rodents, birds and other reptiles develop resistance to the snakes’ deadly venom to survive. But new research led by the University of Colorado Boulder and University of Texas at Arlington sheds light on how snakes manage to keep the upper hand: They maintain a broad and diverse toolkit of genes that encode snake venom, allowing them to adapt as local prey and conditions change.

The findings, published today in Nature Ecology and Evolution, explain how rattlesnakes have kept up with prey species evolving resistance to their venoms over millions of years. This research overturns decades of thought on what factors shape venom gene evolution and venom variation, and sheds new light on why developing effective antivenom treatments for snakebites remains so challenging.

Snake venom, an evolutionary adaptation, is made up of different enzymes and toxins that enable snakes to capture their prey. For decades, biologists have thought that co-evolution between predator and prey would drive snake venom to become highly specialized: the venom evolving to effectively kill specific prey and unused venom gene genetic diversity disappearing along the way. Known in evolutionary biology as “directional selection,” this process is like the sharpening of a knife—while the weapon gets more deadly, it loses a bit of itself in the process.

The new study proposes that instead, “balancing selection” is the mechanism at play, an evolutionary process where multiple versions of a gene—in this case, genes that encode venom proteins—are maintained instead of eliminated. This could be the key to how snakes prevent themselves from going down evolutionary dead ends.

Let’s pause and consider this statement: “Snake venom, an evolutionary adaptation”. How would this work? “To [subdue their prey], venom is injected via the use of a venom delivery system. The venom delivery system includes a postorbital venom gland on each side of the upper jaw that is associated with specialized venom-conducting fangs or teeth.” (Springer) Not only does the snake need the venom, it needs to be able to store it and deliver it without harming itself in the process. Sounds mildly reminiscent of an irreducibly complex system.

“Our findings help explain decades of seemingly contradictory theory and evidence for what drives the extreme variation observed in snake venoms. It turns out that the arms-race between snakes and prey ends up favoring the constant re-shuffling of venom variants that are favored, leading to the retention of lots of venom variants over time, some of which are ancient,” said Todd Castoe, co-author on the study and professor of biology at the University of Texas at Arlington.

Understanding how diverse venomous snake genomes truly are—from rattlesnakes to cobras and coral snakes—can inform advances in anti-venom therapeutics and save lives around the world, Schield said.

See the complete article at Phys.org.

Once again we have adaptation being presented as evolution: "They maintain a broad and diverse toolkit of genes that encode snake venom, allowing them to adapt as local prey and conditions change." - So they "maintain" the genetic toolkit; nothing about where those genes came from. - Then they "adapt" by shifting the mix of toxins in their venom - which genes get used. This is no different from peppered moths, or finch beaks: just another example of microevolution, if even that. Fasteddious
Maybe, maybe and more maybe. "could be" based on what? Your best guess? That's not scientific. Snake venom has no reason to change. It can kill people for centuries. But evolution is all about fictional change so "it must" have changed. relatd
"research on rattlesnakes ... sheds new light ..." Those evolutionists, always ready with a pun and some quick wit for their readers. It's just simple statistics. Say "sheds new light" in every evolutionary news item and eventually you'll hit some comic value in it. David Coppedge taught me of how light is continually being shed upon evolution. It's a theory that needs quite a lot of "new light" to be shed - since it is a fantasy in a world of darkness. Silver Asiatic

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