Frogs use molecules that act as tiny fangs to get their poison into predators

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A team of researchers from the Amphibian Evolution lab at the Vrije Universiteit Brussel and the Laboratory of Veterinary Bacteriology and Mycology at Ghent University has deciphered how poisonous frogs manage to intoxicate an attacking predator fast enough to avoid begin eaten. In a newly published article , they report on how frogs deliver their toxins to a predator’s bloodstream by deploying a second set of molecules, that make the predator’s mouth and gut permeable. Their findings show that besides large and obvious structures like a snake’s fangs or a wasp’s stinger, toxic animals can alternatively deploy molecules to administer their toxins.

 

The research started with the observation that many poisonous frogs represent an enigma when it comes to intoxicating another animal. On the one hand, they secrete large toxins (peptides and proteins) similar to those found in snakes, scorpions, and spiders. On the other hand, they lack the sophisticated tools we see in venomous animals for fast injection of toxins into an aggressor. Instead, a frog under attack has to rely on absorption of its toxins in the predator’s mouth. Since this is a very slow and inefficient process for large toxins, Raaymakers et al. set out to investigate how these frogs actually manage to intoxicate their predators in time before they are killed.

They suspected that another component of the frog’s poison could hold the answer. This second component consists of so-called antimicrobial peptides, that, as their name suggests, kill microbes by punching holes into their cell membranes. Raaymakers et al. predicted that these antimicrobial peptides could also create holes in cells covering a predator’s mouth, making it more permeable for toxins. By testing combinations of these molecules in both cell models and live snakes, they could see that the presence of an antimicrobial peptide speeds up toxin absorption, leading to increased uptake to the blood stream.

These results show that a frog’s poison can therefore be regarded as a unique defence weapon with its own "stealth" delivery mechanism, consisting of a battery of "chemical fangs" for rapid predator intoxication.


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