Dietary diversity plays a role in the complexity of the venom in pit vipers such as rattlesnakes, copperheads, and cottonmouths.
But new collaborative research by scientists at Clemson University has found that the number of prey species a snake ate did not result in the complexity of the venom. Rather, it was how far apart the prey species were in evolutionary terms.
“It’s not just the diet that causes the variation in venom between snakes. That’s the magnitude 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 species of mammals, its venom won’t be very complex. But if it eats a centipede, a frog, a bird and a mammal, it will have a very complex venom because each component of that venom is affecting something different in one of the different animals that the snake feeds on. “
The newspaper Proceedings of the National Academy of Sciences published the results in an article titled “Phylogenetically diverse diets favor more complex venoms in North American vipers.”
The research could lead to better anti-venoms and serve as a dietary database for other snake researchers.
“Snake bite is a neglected tropical disease. She doesn’t kill a lot of people in the United States, only about eight a year. But it causes lasting injuries such as neurological and tissue damage. Even though we have good anti-venoms, they sure could be. We have produced a library of all species venoms in the United States with a higher level of detail than before, so anyone else who wants to improve the anti-venoms could use this information, ”said Matthew Holding, a former Clemson postdoctoral researcher who is the lead author of the article.
Holding collaborated with researchers from Clemson, Florida State University, Mexico, and Brazil to study the venoms and diets of 46 species of North American vipers, including all those that live in the United States. They then used information about the diets of these species to understand why some venoms are simple and others very complex.
Venoms contain proteins that collectively work to neutralize prey. The number of different proteins it contains reflects its complexity.
“You can think of venom like a snake’s toolbox,” said Holding, who is now a National Science Foundation postdoctoral researcher at Florida State. “A wrench, socket, and screwdriver each have a different use. Likewise, each protein has a different function when the venom is injected into a mouse, lizard or centipede or whatever prey the snake eats.”
“Some snakes have much simpler venoms with fewer components. Some have a lot more. We wanted to understand, from an evolutionary standpoint, why this might be, Holding explained.
Researchers collected venom and venom gland samples from rattlesnakes and American cottons across North America. They used next-generation sequencing techniques to generate the largest dataset of venom gland proteomes and transcriptomes for viperid snakes to date.
Using natural history specimens, the researchers compared the complexity of the venom to the diet of snake species.
“Having a prey database based on natural history specimens was paramount as we could not have done this work without these museum collections. We could not have built a comparative phylogenetic framework to compare diet. snakes and the history of evolution without them, ”said Parkinson, who has a dual appointment in the Forestry and Environmental Conservation Department of the College of Agriculture, Forestry and Life Sciences.
Maintenance of said venom complexity changes in association with the phylogenetic diversity of diets for snakes, with the evolution of both simpler and more complex venoms. The study shows that the degree of divergence between prey species is important for the evolution of target venoms, rather than just the differences between prey species or major taxonomic groups, regardless of how they are phylogenetically related.
Some previous studies have suggested that diet likely caused variation in venom between snakes using rough data. This project used genetic data from the venom gland for more than 250 individual snakes, a more dense sample than any other study to date. The researchers also compiled a detailed prey database. The combination of these data made it easier to understand the cause of the variation in the venom.
“Because we’re using next-generation sequencing tools, we could be doing more than just counting the number of components in the venom. We could get much closer to the genetic sequences that contribute to this trait in these taxa, which had not been done before. Holding said.
The study showed that diet diversity predicts the complexity expressed in three of the four largest families of venom genes in viper venoms. Serine proteases, metalloproteinases, and phospholipases had a positive relationship, which means that the more diverse the snake’s diet, the more complex its venom. But diet does not have the same effect on type-c lectins. Dietary diversity accounts for between 25 and 40 percent of the variation in the complexity of the venom.
“We have generated new questions that other researchers need to address, for example why type-c lectins follow a different pattern of relationship with diet diversity than other gene families and why three quarters remainder of the variation in the complexity of the venom for which we are unable to do so. account, ”Holding said.
Since drugs derived from snake venom are used to treat heart disease, high blood pressure, and blood clots in humans, the better scientists understand the venom, the more they can use it to create human drugs.
“We see the potential downstream for medical or therapeutic uses. But what excites us is asking ourselves, ‘Why are there so many types of snakes in the first place, and within those snakes, why do so many types of venom have so many? many effects on prey or humans? “Tenant said.
This project was supported by the National Science Foundation and the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo. The content is the sole responsibility of the authors and does not necessarily represent the official views of the supporting organizations.