LOGAN -- In the evolutionary arms race akin to rock/paper/scissors, human beats garter snake; garter snake beats poisonous newt; and poisonous newt beats human.
A team of four scientists with Utah State University ties has published a paper in the National Academy of Science's early online edition, posted Monday. The paper demonstrates the fact that specific breeds of snakes around the planet have become resistant to the poison contained in one of their favorite foods, a toxic variety of newt.
The adaptation that allows snakes to survive ingesting tetrodotoxin, or TTX, a poison far deadlier than cyanide, has been found in North American garter snakes and some other snakes of Central and South America, and Asia.
"We were able to break down the genetic basis of the adaptations in each of these snakes," said Chris Feldman, lead author of the study and a USU alumnus who earned his Ph.D. in 2008. Feldman is now a faculty member at the University of Nevada-Reno.
"We found that each snake, ranging from the Neotropical ground snake of Central and South America to the tiger keelback of East Asia, has evolved in almost the exact same way as the garter snakes at the genetic level."
TTX is the same neurotoxin found in puffer fish, which are considered a delicacy that is poisonous if not prepared correctly by rigorously trained sushi chefs. TTX also is believed to be an ingredient in so-called zombie powder, an anesthetic-like concoction that causes humans to initially appear dead and regain a temporary semi-conscious state.
"The snakes' evolution probably began millions of years ago," said Edmund Brodie, Jr., a USU biology professor. "The snakes that were resistant to the toxin were able to feed on a higher percentage of toxic prey. The snakes with lower resistance were at a disadvantage in finding food, which would give them less energy to put into reproduction."
So over time, snakes with high TTX resistance reproduced more, passing the trait to their offspring, Brodie said.
Brodie said snakes in different parts of the world adapted the same way because it was the only option in combating the specific poison.
"It was really the only way to adapt, because the toxin has a specific effect on the sodium channel, so no other change would render them resistant," he said. "It was the only adaptation that solved the toxicity problem."
Brodie said he hopes someday to sample safely prepared puffer fish sushi.
"I would like to do that," he said. "I've never had the opportunity, but I have confidence in the chefs."
Garter snakes are not poisonous, but fearful humans often kill garter snakes that live in yards or gardens. We also unknowingly drive over snakes that are in streets, feeding on road kill.
But in a human/newt culinary encounter, the newt would easily win.
"Humans are quite susceptible to this toxin," said Brodie, who said he has worked with tens of thousands of snakes in his career. "We've got snakes eating amphibians, newts in this case, that have enough toxin to kill several people."
The other two professors involved with the study are Brodie's son, Edmund Brodie III, of the University of Virginia, and former USU faculty member Mike Pfrender of the University of Notre Dame. The team's research is funded by the National Science Foundation.