Researchers find the complexity of snake venom driven by a prey diet

Dietary diversity plays a role in the complexity of venom in snake snakes such as rattlesnakes, brass heads and mouths.

But new collaborative research by Clemson University scientists has found that the number of prey species that have eaten a snake does not cause the complexity of venom. Rather, it was how evolutionarily the prey species differed from each other.

“It’s not just the diet that drives the variation in venom over snakes. It’s the breadth of the diet,” said Christopher Parkinson, a professor in the Department of Biological Sciences at the College of Science. “If a snake eats 20 different kinds of mammals, its venom will not be very complex. But if it eats a millipede, a frog, a bird and a mammal, it will have a very complex venom, because each component of the venom is affected differently in one of the different animals that feed the snake. “

The journal Proceedings of the National Academy of Sciences found the findings in a paper entitled “Phylogenetically diverse diets favor more complex toxins in North American adder”.

The research could lead to better anti-toxins and could serve as a nutritional database for other snake researchers.

Snakebite is a neglected tropical disease. It does not kill many people in the US, only about eight a year. But it does cause lasting injury, such as neurological damage and tissue damage. Although we have good antidotes, it can certainly get better. We “has produced a library with all the species in the U.S. in a higher level of detail than has been done before, so that anyone else interested in improving antidotes can use this information,” said Matthew Holding. a former Clemson postdoctoral researcher who is the lead author of the paper.

Holding collaborated with researchers from Clemson, Florida State University, Mexico and Brazil to study the toxins and diets of 46 species of North American viper, all of which live in the United States. They then used information about the diets of those species to understand why some toxins are simple and others very complicated.

Poison contains proteins that work together to make prey unfit. The number of different proteins it contains reflects its complexity.

“You could consider poison as a snake’s toolbox,” Holding said. He is now a postdoctoral research fellow at the National Science Foundation in the state of Florida. “A wrench, a socket and a screwdriver each used a different one. Similarly, each protein has a different function than the venom injected into a mouse, lizard or centipede or whatever prey the snake eats.”

“Some snakes have much simpler toxins with fewer components. Some have much more. We wanted to understand from an evolutionary point of view why that might be,” Holding explains.

Researchers collected poison and venom gland samples from rattlesnakes and water mice across North America. They used next-generation sequencing techniques to generate the largest collection of snake snake proteome and venom transcriptomes to date.

Using samples from natural history, researchers compare poison complexity with diets of snakes.

“Owning a prey database based on samples from natural history was of paramount importance because we would not be able to do this work without the museum collections. We could not have built a comparative phylogenetic framework around the snakes’ diet and evolutionary history without it. Parkinson said a double appointment in the Department of Forestry and Environmental Conservation at the College of Agriculture, Forestry and Life Science.

Holding said that the complexity of venom is changing in conjunction with the phylogenetic diversity of snake diet, with the development of simpler and more complex venom. The study shows that the degree of divergence between prey species is important for the evolution of targeted toxins, rather than just differences between prey species or large taxonomic groups, regardless of how they are phylogenetically related.

Some previous studies have suggested that the diet probably caused variation in venom in snakes using rough data. This project uses genetic data for venom glands for more than 250 individual snakes, a denser sampling that no other study has done so far. The researchers also compiled a detailed database for prey articles. The combination of these data facilitated the understanding of the cause of poison variation.

“Because we use sequencing tools for the next generation, we can do more than add up the number of components in the venom. We can get much closer to the genetic sequences that contribute to this trait in these taxa, which have not been seen before. is not done., “Holding said.

The study showed that dietary diversity predicts the complexity in three of the four largest venom families in snake venom. Serial proteases, metalloproteinases, and phospholipases had a positive relationship, meaning that the more toxic the snake’s diet, the more diverse it was. But diet does not have the same effect on c-type lectins. Dietary diversity accounts for between 25 and 40 percent of the variation in toxin complexity.

‘We have generated new questions that other researchers may face, such as why c-type lectins follow a different pattern of dietary diversity than other gene families and which explain the remaining three-quarters of the variation in toxin complexity that we are unable to do. not. account, ‘said Holding.

Since drugs derived from snakes are used to treat heart disease, high blood pressure and blood clots in humans, the better scientists understand poison, the more likely they are to use it to create medicine for humans.

‘We see the downstream potential for medical or therapeutic uses. But what excites us is to ask, ‘Why are there so many kinds of snakes in the first place, and within the snakes, why are there so many kinds of poison that have so many? many effects on prey or on humans? “Holding said.