Utah State Scientists See Evolution in Action and Make Their Way Into "Nature"

Since the British naturalist Charles Darwin became famous for developing the concept of natural selection, people have been fascinated with the study of evolution. A new study by scientists from Utah State University, "Evolutionary Diversification of TTX-Resistant Sodium Channels in a Predatory-Prey Interaction," was published in the April 7 issue of Nature adding to the ever-burgeoning body of work demonstrating the importance of Darwin’s ideas.

 

In a study involving toxic newts and the garter snakes that prey upon them, Utah State biology doctoral student Shana Geffeney and Utah State biology faculty mentors Edmund D. Brodie and Peter C. Ruben are documenting the co-evolutionary arms race at work.

 

The newts possess a deadly toxin in their skin called tetrodotoxin. It is the same toxin found in Japanese Puffer fish, and the amount of TTX in a toxic newt can be deadly enough to kill 50,000 mice or up to 10 people. The toxin usually protects the newts from hungry predators, but there is one predator that has become resistant to the toxin – the garter snake.

 

Looking at same species garter snake populations from California to Oregon that enjoy partaking of the poisonous newts, the group discovered how the snakes have evolved the ability to eat their toxic meals.

 

"We have identified a few changes in a sodium channel that alter the ability of TTX to bind to the pore of the channel," said Geffeney. "Different changes appear to have arisen independently in several different populations."

 

The team discovered that sodium channels in the garter snake's muscles have evolved a resistance to the toxin. Sodium channels are responsible for electrical signal transmission in the nerves that initiate muscle contraction. When a predator, other than the garter snake, attacks a newt, the newt's toxin binds to a pore in the sodium channel, and the predator becomes paralyzed.

 

"Sodium channels are so critical to the functioning of organisms that there is not a great deal of variation in the protein among different animal species, but here we see differences evolving among populations within the same species," said Geffeney.

 

According to Ruben, the findings have evolutionary and medical implications. Sodium channels are critical proteins in the body, and understanding how they work is interesting and important, he said. Every human being and many animals have sodium channels, and this research offers specifics to help determine how humans and animals have evolved and how sodium channels do their job.

 

"It's not often that such a big evolutionary question gets answered at this level of detail," said Ruben. "We have the whole story here — behavior, evolution, molecular biology, electrophysiology. It is unusual that all these facets of a story can be connected at once."

 

Geffeney, Brodie and Ruben co-authored the paper with Esther Fujimoto, a former Utah State laboratory technician now with the neurobiology and anatomy department at the University of Utah, and Edmund D. Brodie, III, with the biology department at Indiana University.

 

For more information contact Geffeney.

 

Contact: Shana Geffeney

Writer: Maren Cartwright, (435) 797-1355, maren.cartwright@usu.edu