Monday, October 9, 2017

Why do not venomous animals poison themselves?

Just as we store lethal acids in the digestive tract, some animals isolate their own venom so it does not affect them. Others, however, ooze it from the skin. How do they manage not to be poisoned then?

That the snakes and the snakes do not perish at the hands of their own venom has a relatively simple explanation: its homicidal cocktail is manufactured and is kept in glands that never reach to touch the rest of organs of the animal.

Just as in the human stomach acids and enzymes are made that could digest our own flesh were it not that they are isolated by the gastric wall, lethal brews of snakes do not pose a danger to these animals because they are isolated.

That works clearly when that isolation occurs, but ... what mechanism protects creatures that secrete venom through the pores of the skin?

This is the case of the ghost arrow frog (Epipedobates anthonyi): dressed in colorful red and white stripes, it is a walking arsenal of epibatidine, a neurotoxin so powerful that if an animal comes in contact with it it would increase the tension of blow, it would suffer convulsions , would have difficulty breathing and could fall lifeless in a short time. And yet, the killer frog does not even bother. Her own venom does not tickle her. How is it possible?

Scientists at the University of Texas have also solved this piece of the puzzle. He apparently owes his immunity to a tiny genetic mutation in only three of the 2,500 amino acids of a receptor in his head. A tiny change in the letters of his genome that does not block any of his brain functions but protects it from the lethal cocktail. What is interesting is that this small but vital change has appeared at least three times independently in the evolution of these amphibians. Sign that the formula works.

"Being toxic can be a great advantage to survive, because it keeps away potential predators," says Rebecca Tarvin, lead author of the article, which has been published in Science. So why are not there more poisonous animals? Because it is difficult to develop resistance to one's own toxins. Hence the effort to study the amphibians that have succeeded.

Interest does not end there. It turns out that the receptor on which epibatidine acts is also present in humans, with an important role in both pain perception and nicotine addiction. In fact, it is attributed an analgesic activity 250 times more powerful than that of morphine, and without side effects. The only thing that prevents it from being applied is that it is too toxic.

That, however, could be avoided if we were able to emulate nature by editing some letters of the DNA to immunize us in front of the poison and remain only with its advantageous properties.

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