To the Death

The super-toxic newt (Taricha granulosa) in this picture may appear to be losing the fight against one of its only predators - the garter snake (Thamnophis sirtalis).  But at the molecular level, the prey may be calling the shots.

The newt carries a poison in its skin called tetrodotoxin (TTX).  This paralyzing substance is also found in puffer fish and octopuses, and there are claims that it is the voodoo "zombie" drug. 

One-thirtieth of the TTX normally found in T. granulosa is enough to kill the average human being.  The toxin interferes with vital sodium channels in nerve cells.  The only organisms on Earth that can eat the newts and survive are some garter snakes.

"Sodium channel genes in different vertebrates are virtually identical to each other, but not in these snakes," said Edmund Brodie III from Indiana University. "We're finding a molecular arms race is driving rapid and repeated changes in the gene within this group of beasts."

Brodie and his colleagues believe that over time the newts have increased their toxin levels - forcing the snakes to restructure their sodium channels in a deadly game of poison/antidote one-upmanship.

The results were published in the April 7 issue of Nature.

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 -- Michael Schirber

Credit: Edmund Brodie III