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Some of the world’s most poisonous animals are small and colorful frogs called poisonous frogs, from the Dendrobatidae family, which live in the tropical rain forests of Central and South America. A single frog carries enough poison to kill 10 adult humans. Interestingly, these frogs are not born poisonous – they acquire their poisonous chemical by eating insects and other arthropods.
But if this poison is so deadly, why don’t the frogs themselves die when ingesting it?
The ability of these frogs to prevent self-poisoning has long puzzled scientists, said Fayal Abderemane-Ali, a researcher at the Cardiovascular Research Institute at the University of California at San Francisco and lead author of a new study. on the Journal of General Physiology which explores this phenomenon.
Related: What to do if you are bitten by a poisonous snake?
In the new article, the researchers studied poisonous frogs of the genus Phyllobates which use a toxin called batrachotoxin, which works by disrupting the transport of sodium ions entering and leaving cells – one of the most important physiological functions of the body. When your brain sends signals to the body, it sends them through electricity. These signals send instructions to parts of the body, such as your limbs to tell them to move, to muscles to tell them to contract, and heart to tell him to pump. These electrical signals are made possible by the flow of positively charged ions, such as sodium, through negatively charged cells. Ions enter and exit cells through protein gates called ion channels. When these ion channels are disrupted, electrical signals cannot pass through the body.
Batrachotoxin causes ion channels to stay open, resulting in a free flow of positively charged ions into cells, Abderemane-Ali told Live Science. If these fail to close, the entire system loses its ability to transmit electrical signals.
“We need these channels to open and close to generate electricity that runs our brain or heart muscles,” Abderemane-Ali said. If the channels just stay open, “there is no cardiac activity, there is no neuronal activity or contraction activity.”
Basically, if you ingest one of these frogs, you die almost immediately.
So how do these frogs and other poisonous animals avoid suffering the same fate? There are three strategies poisonous animals use to stop self-poisoning, Abderemane-Ali said. The most common involves a genetic mutation that slightly changes the shape of the toxin’s target protein – the sodium ion gate – so that it can no longer bind to the protein. For example, a species of poisonous frog called Dendrobates tinctorius azureus carries a toxin called epibatidine that mimics a beneficial signaling chemical called acetylcholine. According to a 2017 study published in the journal Science, these frogs developed adaptations in their acetylcholine receptors that slightly altered the shape of these receptors, making them resistant to the toxin.
Another strategy, used by predators of poisonous animals, is the ability to completely get rid of the toxin from the body, said Abderemane-Ali. This process is not necessarily the same as avoiding self-poisoning, it is just another way for animals to avoid being poisoned by the things they eat.
The third strategy is called “sequestration”.
“The animal will develop systems to capture [or] to absorb the toxin to make sure it doesn’t cause problems for the animal, ”said Adberemane-Ali.
In Adberemane-Ali’s study, he cloned sodium ion channels from Phyllobates frogs and treated them with the toxin. He was surprised to see that the sodium-ion channels were not resistant to the toxin.
“These animals should be dead,” said Abderemane-Ali. Because the sodium-ion channels of the frogs did not resist the disruptive effects of the toxin, the frogs should not be able to survive with this toxin in their bodies.
Based on these results, Abderemane-Ali suspects that these frogs most likely use the sequestration strategy of avoiding auto-intoxication by using what he calls a “protein sponge”. Frogs are likely producing a protein that can absorb and hold the toxin, which means the toxin never gets a chance to reach these vulnerable protein channels in the first place.
American Bullfrogs (Rana catesbeiana) also use forcible confinement, said Abderemane-Ali. These frogs produce a protein called saxiphilin, which can bind to and block the saxitoxin toxin. Saxiphiline is currently being investigated as a potential solution to neutralize toxins introduced into our water supply by harmful algae blooms.
Originally posted on Live Science.
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