Venom Variation in Snake Species

The lack of venom variation discovered in a certain snake species is challenging the conventional theory of how these toxins evolve in these slithering reptiles, as well as provides crucial information for snake conservation, according to a new study.

Each venomous snake species produces a unique venom mixture of around 50-200 toxic proteins that evolve depending on the snake's diet. For example, the eastern coral snake tends to eat smaller reptiles while rattlesnakes prefer the taste of rodents. And over the course of this predator-prey relationship, snakes tweak their venom recipe so that it remains effective and their victims don't develop a resistance to it. Consequently, snakes of the same species should all boast different venom diversity depending on their local habitat and diet. That's why venom from an eastern diamondback rattlesnake in the Everglades is distinct from the cocktail of toxins delivered by the same species in the Florida panhandle area, some 500 miles away.

However, that's not what lead author Darin Rokyta, of Florida State University, and his colleagues saw when they studied eastern coral snakes in Florida. For the results of a large-scale survey showed that the venom of the eastern coral snake is always the same, no matter what part of the southeastern United States they were from.

"We were shocked," Rokyta said in a statement. "This is the first time anyone has looked at venom variation at this scale, and everybody has assumed that the co-evolutionary arms race would cause local populations to diverge quickly."

Researchers suggest that this could be the result of a small population of eastern corals having recently taken over the species' entire range, or a difference in co-evolutionary dynamics between the species and its typically reptilian prey.

Regardless of the reason, the data from this study can be used to help manage snake populations to ensure that the full range of venom subtypes are conserved for the long-term viability of the species.

The results are described further in the journal Genetics.

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