If you were viewing a list of the world’s most poisonous animal species, you’d be hard-pressed not to see a poison dart frog on it. Although they’re small, just 2 inches fully grown, they contain enough of a lethal toxin to take out at least ten adult humans.
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The toxin causes serious problems when it gets into the bloodstream. Within minutes, it blocks the normal function of nerve cells’ sodium channels, allowing muscles to contract but not relax; this is especially dangerous for the heart, which can stop pumping blood as a result.
The active ingredient in the toxin is a chemical called batrachotoxin. While batrachotoxin is hazardous to humans and countless other animals, researchers have always wondered why it doesn’t seem to impact other poison dart frogs that get exposed to it.
To learn more, researchers from the State University of New York (SUNY) took a closer look at the golden poison frog (Phyllobates terribilis). The findings of their study are published in the Proceedings of the National Academy of Sciences (PNAS).
Because a puffer fish's tetrodotoxin works in similar ways to the poison dart frog’s batrachotoxin, they used what knowledge they could scrape together from puffer fish toxins as a starting point for their research.
Puffer fish’s immunity to tetrodotoxin stems from an amino acid mutation. With that in mind, the researchers studied the amino acids in poison dart frogs to find some clarity into their immunity to batrachotoxin.
To discover if an amino acid(s) was responsible for their resistance, the researchers turned to lab rat muscle for testing. They introduced all five of P. terribilis’s amino acids to the test muscle, and just like that, it became immune to the effects of batrachotoxin.
From this observation, it became apparent that an amino acid (or some combination of the five) was responsible for the poison dart frogs’ immunity to batrachotoxin. Nevertheless, the researchers wanted to pinpoint which of the five amino acids was behind the immunity, so the testing continued.
They later introduced each of the five amino acids to additional lab rat muscles, one at a time, until the resistance began kicking in. Out of the five amino acids tested, only one of them seemed to provide the effects the researchers were looking for: one known as N1584T.
Many initially thought that several factors were behind the poison dart frog's immunity to batrachotoxin, so it was surprising to find that a lone amino acid was behind these anti-toxin mechanisms.
The researchers point out how the results of this study are unlikely to lead to cures for humans impacted by the effects of batrachotoxin, but it was still intriguing to learn about how the animals remain immune to their own toxins through evolution.