Tetrodotoxin and Evolution

Interesting article by Sean Carroll of the NY Times about tetrodotoxin, the poison that makes puffer fish (fugu) and several other species of unrelated animals deadly. The puffer fish, newts, and toads don't make the poison, but rather concentrate in their organs bacteria that make it. They can do this because they have evolved resistance to the poison, and biologists have now identified the precise chemical mechanism of the resistance and the exact gene mutations responsible for it.