One-thirtieth of the TTX normally found in a T. granulosa newt is enough to kill the average human being. The only organisms on Earth that can eat T. granulosa newts and survive are some T. sirtalis garter snakes. TTX is a defensive compound found in some puffer fish, octopuses and primitive chordates. It is used in low concentrations to treat morphine and heroine addicts. It's also the "zombie" drug used by Haitian voodoo ritualists.
Despite its action at the molecular level, the evolution of TTX in some organisms is viewed by ecologists as a defense mechanism. In the case of T. granulosa newts and T. sirtalis garter snakes, the interaction has gone far beyond that simple fangs-off arrangement, evolving into a lethal contest of toxification/detoxification one-upsmanship.
"One might think that this sort of change in the sodium channel would be too costly to the snakes," said Utah State University biologist Shana Geffeney, who conducted the gene expression experiments. "What will be interesting in the future is to understand if there is a balance between the costs of the changes in the channel pore structure on channel function and the benefits of changes in TTX binding."
The evolution of new traits often happens one of two ways, either by altering existing genes or by changing patterns and amounts of expression. The current Nature report shows that snakes' ability to detoxify TTX involves changes in the sodium channel gene.
"That is generally the story as it is developing," Brodie said. "Ecological arms races that go on between predator and prey are really driven at the molecular level. We have no evidence, nor reason to believe, that TTX is changing too, but rather that the toxin responds in quantity. Pour on more toxin, change the snake's sodium channel. Add more toxin, force further changes in the channe