Snake Evolved to Have Opposite Toxins in One Venom, Research Shows

Snake Eating Lizard
A green vine snake feeds on a lizard in Kerala, India. The Amazon puffing snakes lives in trees and also feed on lizards, as well as on birds and rodents. ABHISHEK N. CHINNAPPA/REUTERS

The Amazon puffing snake has been hiding a secret weapon—one that can attack multiple prey.

In a new study from University of Northern Colorado and National University of Singapore scientists, this snake's venom was found to have a unique property. Published on August 1, the research indicates that the snake's venom has likely evolved so the snake can continue to survive.

The Amazon puffing snake, or Spilotes sulphuereus, can grow to be around 8.9 feet long. Despite its length, the snakes are not strong constrictors, so they rely on their venom to be able to kill their prey. These snakes live hidden in the trees in South America, have large eyes and their venom flows quickly out of their fangs.

Stephen Mackessy, a professor at the University of Northern Colorado, and his team, which includes his PhD student Cassandra Modahl, captured three of these snakes. They then extracted the 6-foot-long snakes' venom and analyzed it to see which toxins were present.

"It was quite a surprise because it's something we haven't seen before," Mackessy told Newsweek of their finding.

The team found the toxin sulmotoxin 1 in the venom, which is deadly to mammals but doesn't harm birds or lizards. They also found the opposite: sulditoxin. Sulditoxin is lethal to birds and lizards, but not to mammals. The team discovered that even when the dose of sulditoxin is 22 times higher than what an Amazon puffing snake delivers in its bite, sulditoxin still won't kill a mammal.

The snakes typically eat birds and lizards but will occasionally eat rodents as well. Mackessy says that the snake likely used to only eat birds and lizards and only added rodents to their diet later on. This could have caused the animals to evolve to have this second, mammal-killing toxin to be able to incorporate the more calorie-heavy mammals into their diet.

"You get more bang for your buck with mammals than you do with lizards," Mackessy explained. This can also help the snakes to diversify and be able to kill any invertebrate animals they encounter, such as a predator. Since the mammals came into their diet later, that could explain why the snake developed two separate toxins instead of just one that can kill birds, lizards and mammals.

Mackessy thinks studying these venoms can mean a lot for humans as well. "Looking at animal venoms and understanding the mechanisms of how some of these toxins work actually provides us insights into how our own systems work, and also are a possible source of new therapeutic drugs," he said.