Charmander #004

A newt is a semiaquatic salamander. Newts tolerate both aquatic and terrestrial habitats. Newts undergo metamorphosis. The first stage of the life cycle of a newt is aquatic while the second stage is terrestrial. Adult newts appear lizard-like.

California Newt (Taricha torosa)

Connor Long (CC BY-SA 3.0)

The California newt (Taricha torosa) and rough-skinned newt (Taricha granulosa) and are salamanders native to North American. They are known for producing a toxin found on the skin surface.

The belly of the newt is orange/yellow. When it stands up, the color acts as a warning signal to potential predators. From above, the brown/olive color allows the animal to blend in with its surroundings.

The neurotoxin tetrodotoxin (TTX) produced by this genus is potent. The newt emits an acrid smell to warn predators to avoid it. TTX is also found in harlequin frogs and pufferfish (Striedter et al. 2013). The toxin passes through cell membranes and binds to voltage-gated sodium channels. The TTX molecule clogs the channel, blocking the sodium ions in nerve cells and preventing the electrical signals for nerve function. Inhibiting the firing of action potentials induces paralysis.

This genus has evolved resistance to the toxin. A genetic adaptation provides the newt with protection against TTX. The protein structure of the voltage-gated sodium channel has a slight alteration, which can be traced to a change in the sequence of the DNA. This adaptation allows the newt to survive exposure to TTX (Striedter et al. 2013).

Rough-skinned newt (Taricha granulosa)

The High Fin Sperm Whale (CC BY-SA 3.0)

Striedter, Georg F.; Avise, John C.; Ayala, Francisco J. (2013). In the Light of Evolution: Volume VI: Brain and Behavior. National Academies Press. ISBN 978-0-309-26175-3.