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Venomous snakes produce some of the world’s deadliest substances, so they have to be pretty careful about how they use it. But what happens if they accidentally inject themselves with their own harmful cocktail?

Hosted by: Rose Bear Don't Walk

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Go to Brilliant.org/SciShow to learn how to take your STEM skills to the next level. [♪ INTRO] . Snake venoms are some of the world’s deadliest substances.

So snakes have to be super careful with them. I mean, if you have giant muscles, you don't want to punch yourself in the face. And obviously, if you have potent venom, you don't want to accidentally bite yourself… or, so you’d think.  But actually, in most cases, if a snake bites itself, it's pretty anticlimactic.  We've known this for a long time.  Over the centuries, a not-so-small number of perhaps ethically-questionable scientists have found themselves overcome with morbid curiosity.   So they’ve injected snakes with their own venoms to see what would happen.

And, the short answer is usually: very little, if anything at all. Most venomous snakes simply aren’t a danger to themselves, even though, in other animals, their venoms do some serious damage. Snake venoms are full of toxic peptides and proteins, molecules that cells make that cause all sorts of horribly, horribly unpleasant things.

Like, neurotoxic venoms mess with neurons and keep them from sending signals properly.  And that means, at their worst, they can cause life-threatening paralysis. Meanwhile, hemotoxic venoms do terrible things to your circulatory system, like preventing blood clotting and causing uncontrolled bleeding. Some snakes even wield cytotoxic venoms: ones that kill cells and can cause parts of your body to simply die.

All of these toxins tend to do their nefarious work using elements of cells that are found across vertebrate lineages, and even in invertebrates like bugs. Essentially, you can think of the toxins as keys that unlock really standardized doorknobs found in all sorts of buildings. That’s why they’re dangerous to us, even though we’re not the buildings they’re trying to break into.  And why it’s weird they’re usually not dangerous to themselves, even though they have the same kind of doorknobs.  Ok, the analogy might be getting a little strained, but I think you get the picture.  We didn’t figure out how the snakes were surviving their toxic cocktails until somewhat recently.

And, it turns out, they can each have several strategies. For starters, even though venom toxins tend to attack really important pieces of our biology, some snakes are able to tweak their versions of these targets. It’s the molecular equivalent of changing the locks.  For example, since neurotoxins are positively charged, they’re attracted to negatively charged parts of receptor proteins on nerves.  But certain species of snake have just, you know, reversed the polarity of their receptors.

See that trick isn’t only useful on the Starship Enterprise! Instead of negatively charged receptors, they have positively charged ones that literally repel the positively charged toxins. And this isn’t just seen in venomous snakes that need to protect themselves.  Some non-venomous snakes have similar tweaks to their receptors, presumably to help stay off their cousins’ menu.

Other snakes, like the Egyptian cobra, are able to tack sugars onto their nerve receptors, which physically block the toxins from reaching their target. But it’s not always possible to modify the stuff toxins attack.  Changes can mess things up, and remember, these are super important parts of our bodies, so trying to toxin-proof them could be life-threatening all on its own. So, some snakes have built-in antivenoms.

Biologists have suspected venomous snakes essentially “leak” toxins into their bodies constantly. This lets their immune systems develop targeted defenses, much in the same way a vaccine prevents you from coming down with a disease. But some take this idea one step further.

They’ve evolved anti-toxins that they keep in their bodies all the time. That way, if some of their venom gets where it doesn’t belong, the most dangerous bits are shut down before they can cause real harm. For instance, some snakes produce proteins that bind and inhibit their venom’s phospholipases: enzymes responsible for a lot of the nasty effects of hemotoxic and cytotoxic venoms.  These versatile enzymes can do a range of awful things, like prevent blood clotting and kill cells.

So it’s no wonder that snakes like the short-tailed pit viper have several different phospholipase inhibitors in their blood. What’s extra cool about natural inhibitors is that they could help us develop better antivenoms.  Modern antivenoms save a lot of lives, but they’re not perfect. They’re expensive, only cover a limited number of snakes, and generally require cold storage, which means it can be hard to get them to the people who most need them.

So doctors would love to find a good alternative, and the snakes’ own natural inhibitors hold a lot of promise.  Before we wrap this up, it’s worth noting that not all snakes have these built in protections. Some can and have killed themselves with a misplaced bite. Like, in 2016, Australian researchers witnessed the unfortunate death of a brown tree snake that bit itself, which suggests that brown tree snakes aren’t immune to their own venom.

And even ones that are may not survive the bite from other members of their own species, since there can be a lot of toxin variation between individuals.  Like, in 1932, scientists made a couple of black-tailed rattlesnakes bite each other, and let’s just say that things did not end well for either rattlesnake. In many cases, though, the animal’s built-in venom defenses can prevent personal tragedy. So while I imagine it’s super embarrassing for a snake to accidentally bite itself, most can slither away mumbling “I meant to do that.” If you liked this episode of SciShow, and want to learn more about the world around you, you might like the courses offered by today’s sponsor, Brilliant.

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