There would be little point in having the ability to lethally poison a predator if you accidentally poisoned yourself and ended up just as dead.
In the case of poison dart frogs, they dodge being poisoned twice in the process of protecting themselves. Initially, the frogs ingest a toxin from the ants, mites and centipedes they consume, which have been eating poisonous plants. Though research on the subject is ongoing, scientists believe the ant toxins don’t harm the frogs because of a protein in their gut, which is released as the ants are digested and interacts with the poison.
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Essentially, this protein binds to the toxins and carries them through the frog’s bloodstream to the skin, where they end up in structures known as granular glands. These glands produce secretions full of the acquired toxins and coat the frog’s skin: the process is rather like wrapping up the poison molecules in tiny bags and shipping them to a distribution centre before they can do the frogs any harm.
The beneficial effect of having the waste toxins coating the skin is that any predators attempting to eat the frogs risk swallowing a lethal dose that would paralyse their breathing and cause heart failure – just as would happen to the frogs if they didn’t have their special proteins.
This is all well and good, but the frogs must also keep themselves clean and interact with other frogs. So the proteins come into play again to prevent accidental poisoning by the animals directly ingesting toxin from their own skins.
What about venomous animals?
Similar proteins play an important part in the self-protection of venomous animals, too – those that kill their prey by biting or stinging. A cobra, for example, could theoretically accidentally bite itself. More to the point, though, why doesn’t a snake die when it eats a prey animal it has just bitten and pumped full of toxins?
As with the frogs, special proteins in the snake’s digestive system neutralise the harmful substances so they pass out of the body in the normal way, without causing the snake any damage. In addition, if venom ends up in a snake’s bloodstream because of biting itself or another snake of the same species, antibodies in its immune system bind to the venom particles and block them from harming any cells. These now-harmless parcels are conveyed to the kidneys and then flushed out of the body.
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Top image: a pair of blue poison dart frogs. Credit: Getty
