Among mushroom foragers,  the Death Cap is infamous.

It's the most poisonous  known mushroom in the world, and just half of one contains  enough poison to kill you. This little guy may look  unassuming, but it's responsible for 90 percent of poisonous mushroom deaths globally.

So you might assume that it's  about as bad as it could be. But you would be wrong. Because recent research shows that the Death Cap is developing new toxins that  may make it even deadlier. [♪ INTRO] Meet Amanita phalloides,  commonly known as the death cap.

Appearance-wise, they’re pretty innocuous. With a white stem, a yellowy-brown cap,  and beautiful gills along the underside, they look pretty much like any  basic drawing of a mushroom. But they have that ominous name for a reason.

They pack a double punch of being  easily mistaken for friendly snacks like the puffball or straw  mushroom, and having some of the highest toxin levels per gram out  of any other species of mushroom. With these guys, there’s not  mush-room for error... I’m sorry.

Death caps have allegedly been behind  the deaths of many historical figures, including the accidental  poisoning of Pope Clement VII, and the murders of Holy Roman Emperor Charles VI and Roman Emperor Claudius. Now, we don’t generally tell  you what to do here at SciShow, but if you are a Roman emperor,  just stay away from mushrooms! Death caps are tough to neutralize, too.

Unlike some other mushrooms, even cooking or drying does not keep you safe from their toxins. Don’t believe me? Ask the family of a woman  in Australia who, in 2023, cooked up beef wellington made with death cap mushrooms that had been dehydrated.

Oh wait. You can’t. It turns out she did it on purpose — they  are dead, because they where murdered.

It probably seemed like the perfect crime, because you might not notice that  something is wrong right away. The first symptoms only start  about 6 hours after your meal, and then it’s nausea, vomiting,  and diarrhea for up to 36 hours. You’ll even start to feel better for a while.

If you go to the hospital for your  early symptoms, you might be discharged. But in the background, the death cap toxins  are settling into your kidneys and liver. Ultimately, that’s what kills you: liver  failure 3-5 days after eating the mushroom.

So, yeah. These mushrooms are definitely deadly. A. phalloides jams your system  with three main types of toxins, but the one that’s the worst  for humans is called amatoxin.

Amatoxin permanently binds to an  enzyme called RNA polymerase II and stops it from doing its very important job of transcribing all of your genes into proteins. And it works so fast that when your liver  and kidneys try to do their usual work of filtering toxins out of your body,  they can’t clear it out and end up getting stuffed with the very  poison they’re trying to get rid of. But even after all of that, the  survival rate of death cap poisoning is still estimated to be around 80-90%.

So odds are a quick brush with death  cap will not be the end of you. But to boost your chances, it’s important  to get treatment as soon as possible. While there are still no official  antidotes to amatoxin poisoning, doctors can give you activated  charcoal to soak some of it up, or certain medications to try to prevent  too much amatoxin from reaching your liver.

And you want to do that soon, because once enough of your  liver and kidney cells die off, that damage is permanent. In some situations, even people  who survive death cap poisoning might need a liver transplant or kidney dialysis. But before I get to the part about this  toxic mushroom gaining even more toxins, I need to pause for a quick break.

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They’re also giving you unlimited daily access to everything on Brilliant with 20%  off an annual Premium subscription. Now, we could not get a death cap  to speak with us on the record, but it doesn’t seem that  they’re targeting us on purpose. Humans are probably just unlucky victims as this mushroom adapts to its environment.

Remember that 6 hour delayed toxicity? It doesn’t stop humans from eating  the mushroom in the first place, so that gives us a pretty good idea that  death cap poisons aren’t really all about us. In fact, people who have eaten a death cap and lived to tell the tale have reported  that it’s actually pretty dang tasty.

But not worth it. Don’t eat death caps So if they’re not deterring us, some  scientists think that the death cap’s toxins help ward off smaller predators,  like pests and rival fungi. This would mean that A. phalloides might have developed amatoxin as a defense  against mushroom-eating insects.

Now, some species of the Drosophila fly  have developed a resistance to amatoxin, so it’s not a perfect defense. But the flies wouldn’t need to evolve a specific resistance to it if the toxin  didn’t affect them significantly. So this makes some researchers  support the insect deterrence idea.   Another possibility is that  these toxins help death caps establish a symbiotic relationship  with the trees they grow on.

The thing is, because of that relationship, A. phalloides are difficult  to study in a lab setting. Not too many labs have extra  room for a bunch of trees, however nice the atmosphere would be. So while we know for sure that  they’re toxic to humans and dogs, studies on toxicity in other  species are spore-adic at best.

Sporadic? SPORE-adic? And that’s not great because these mushrooms have started invading new territories.

They used to be European exclusives, but now they’ve spread their deadly  poisons across North America and Australia. And a 2023 publication found that as A. phalloides adapts to new environments,  it’s coming up with new toxins. They’re killing it out there!

Sometimes literally. This was studied in 88 death caps  across California and Europe. Researchers were specifically assessing  a group of genes called MSDIN genes, responsible for coding the most  potent of the death cap toxins, including the ones most deadly to humans.

They found that these MSDIN  genes have become significantly different between the US and European varieties. And they seem to be undergoing  very strong natural selection. See, each individual mushroom has a  slightly different sequence of MSDIN genes.

But, despite that variation,  some regions of the genome stay pretty much the same no matter  where the mushroom is growing. The fact that some of the genome has stuck around, despite other parts being different,  suggests that those retained parts of the MSDIN genes, and the amatoxins they  encode, probably aren’t just a coincidence. Death caps are probably developing  new poisons in new environments because something about those toxins is helpful for keeping the next generation thriving.

So it’s quite possible that these  selectively-refined toxins have helped A. phalloides successfully  sprawl across the globe. Caps off to evolution as always. And that’s just what we know from the  few death cap genomes we’ve looked at!

There’s a huge diversity of  MSDIN genes among A. phalloides, so they’ve made many new toxins  that we humans have yet to study. So, the moral or perhaps  morel of the story is not to eat anything that you have  foraged unless you are 100% sure. As for me, I’ll probably stick to  the ones I can buy in the store. [♪ OUTRO]