Rough-skinned Newt

The rough-skinned newt (Taricha granulosa) is a salamander of the Pacific Northwest whose skin contains tetrodotoxin, among the most potent natural toxins known. It is a classic example of a coevolutionary arms race.

🧬 Field Guide Specimen: Open Rough-skinned Newt in the CRV Science Field Guide to log the specimen, see its place among the Tetrapoda lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.

The toxin blocks voltage-gated sodium channels, stopping nerves from firing and causing paralysis. A newt carries enough to kill several adult humans, though poisoning happens only if one is swallowed. The animal displays a bright orange belly in an "unken reflex" when threatened.

Common garter snakes (Thamnophis sirtalis) in newt territory evolved mutations in their sodium channels that make them resistant. In some places the most toxic newts live alongside the most resistant snakes, and each escalates in response to the other. Edmund Brodie and colleagues documented the pattern.

The origin of the toxin is debated; it may be produced by bacteria associated with the newt, similar to pufferfish. Amphibian metamorphosis and breeding migrations make newts easy to find on land and in ponds in the rainy season.