How do poisonous animals like the hooded pitohui, a small, drab bird whose orange and black feathers are laced with poison, keep from poisoning themselves? For decades, the best theory has been that the birds and frogs evolved specially adapted sodium channels. But a study in the Journal of General Physiology overturns that notion. The researchers provide evidence that pitohui and poison frogs have what they call "toxin sponges," or proteins that mop up the fatal toxins before they cause damage. Rebecca Tarvin, an evolutionary biologist at University of California, Berkeley, who has researched how poison frogs tolerate another neurotoxin called epibatidine, is impressed by the results. "Especially given my line of research, I was very surprised to see that the sodium channels of (poison frogs) are not sensitive to batrachotoxin, which is not what we had predicted," says Tarvin, who is also a National Geographic Explorer. But she also cautioned against overgeneralizing the results. "This is only one of the many toxins that the frogs have," she says. "But for the case that they tested, I'm convinced."
August 5, 2021