This squeaky yellow frog may look cute, but it’s not to be trifled with: just a milligram of its venom is enough to kill up to 20 people. The frog protects itself against this toxin in an unusual way.
The terrible poison dart frog (Phyllobates terribilis) rightly bears its name: Its poison, the batrachotoxin, makes it the most poisonous frog species known to date and one of the most poisonous animals of all. Just one milligram of this toxin stored in the frog’s skin glands is enough to kill ten to 20 people. The poison blocks the sodium channels of cells and thus paralyzes the nerves, heart and muscles.
The enormously toxic effect of this poison raises the question of how these frogs, which only occur in a small area near the Pacific coast of Colombia, protect themselves from this toxin. One possibility would be that they have developed sodium channels that are resistant to the batrachotoxin. But that is not the case, as recently discovered by researchers working with Daniel Minor from the University of California in San Francisco. The ion channels do not have a protective mutation, nor are they otherwise immune to the poison.
But how does the frog protect itself then? Further analyzes showed that the isolated sodium channels reacted sensitively to the poison, but if the batrachotoxin is injected into the living animal, hardly any of it seems to arrive at these channels. Minor and his team suspect that special proteins play a crucial role in this. These absorb the small poison molecules like a sponge and bind them to themselves. This will keep the poison away from the sodium channels.
“This keep-away strategy provides the frogs with an overarching method of protection against poison and also helps them protect the processes and tissues required to transport and collect the poison,” says Minor. “A better understanding of these protective mechanisms could also lead to the discovery of better antidotes against such potent toxins.”