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Why poison frogs donít poison themselves

Phantasmal poison frog <em>Epipedobates anthonyi</em>

The phantasmal poison frog Epipedobates anthonyi is the original source of epibatidine, discovered by John Daly in 1974. Epibatidine has not been found in any animal outside of Ecuador, and its ultimate source, proposed to be an arthropod, remains unknown. This frog was captured at a banana plantation in the Azuay province in southern Ecuador.

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Although tiny, dappled in cheerful colors and squishy, poison frogs in fact harbor some of the most potent neurotoxins known to man. Now, researchers from The University of Texas at Austin (UT Austin) are a step closer to answering the question: How do these frogs keep from poisoning themselves? The answer has potential consequences in the fight against pain and addiction.

The research answers this question for a subgroup of poison frogs that use the toxin epibatidine. The frogs use the toxin to keep predators from eating them. Epibatidine binds to receptors in an animal's nervous system and can cause hypertension, seizures and even death. The researchers found a small genetic mutation in the frogs -- a change in just three of the 2,500 amino acids that make up the receptor -- prevents the toxin from acting on the frogs' own receptors, making them resistant to its lethal effects. They found that precisely the same change appeared independently three times in the evolution of these frogs.

"Being toxic can be good for your survival -- it gives you an edge over predators," said Rebecca Tarvin, a postdoctoral researcher at UT Austin and a co-first author on the published study. "So why arenít more animals toxic? Our work is showing that a big constraint is whether organisms can evolve resistance to their own toxins. We found evolution has hit upon this same exact change in three different groups of frogs, and that, to me, is quite beautiful."

Read more about this research in the UT Austin news story Why Poison Frogs Donít Poison Themselves. (Date image taken: August 2017; date originally posted to NSF Multimedia Gallery: July 20, 2018)

Credit: Rebecca Tarvin/University of Texas at Austin
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