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Do you ever find yourself wondering what the most toxic animals, plants, and things on Earth could be? From daffodils to dangerous snakes, here's a collection of episodes about our favorite poisonous, venomous, and generally deadly organisms! Let's go!

Hosted by: Stefan Chin

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Original Videos:
Good News: Daffodils Are The Worst:
The Oversized Invasive Carrot That Can Give You Third Degree Burns:
The Little Apple of Death:
Poor, Misunderstood Poison Ivy:
Behold—Poisonous Snakes! (Yes, You Read That Right):
Can You Drink Snake Venom?:

 (00:00) to (02:00)

-[Stefan] Nature is beautiful but also sometimes very dangerous. Like you might think plants are pretty chill, but some wake up every day and choose violence. And there are critters that wield both poison and venom! And that's just the tip of the iceberg. So keep your hands inside the vehicle because it's about to get toxic.

We'll kick it off with innocent little daffodils; those iconic symbols or spring. Well it turns out these cute little flowers are also cold-blooded killers.

-[Olivia] Aw, daffodils. Those cheery, usually yellow symbols of spring; they're also cold-blooded killers. They're not only toxic to us and our pets, they're toxic to other plants. But turns out there are some big reasons to be thankful for that.

All plants in the genus Narcissus, otherwise known as daffodils are poisonous from bulb to bloom. We've actually talked about their toxicity before because one chemical they have, called lycorine, poses a threat to people and pets. But it turns out flowers also kill their petalled peers.

If you put fresh cut daffodils in the same vase as, say, tulips or roses, you'll notice the other flowers quickly become wilted and their leaves yellowed. And I do mean quickly. A daffodil can reduce a rose's vase life from 11 days, down to 3. Or a tulip's vase life from 7 days to 4.

Florists call this the "vase effect" and it's thanks to the daffodils' stems. They're full of a toxic sap called mucilage. So when the flowers are cut sap flows from the stem. This wouldn't be so bad, except that when they're put in the same vase other flowers use their stems as straws to suck up water.... and whatever's in it. Like poison.

Different parts of the mucilage can kill different flowers too. Roses, for example, are done in by its sugar, though indirectly. See, the sugar is a feast for bacteria in the water. And since rose stems don't have much of a microbiome to protect them, those bacteria can get inside and plug them up. Keeping the flower from getting enough water.

 (02:00) to (04:00)

Meanwhile, species like tulips have to contend with narciclasine. That's an alkaloid so it's in the same class of molecules as caffeine and nicotine. And while it's not exclusive to daffodils, it's still bad news.

Research has shown that it can kill plants in a bunch of ways. It inhibits cell division and protein synthesis, both of which are kind of deal breakers for staying alive. And it can interfere with the plant growth hormone, auxin. So narcislasine can jam almost all of the signals that poor tulip needs to stay beautiful. Luckily florists get around the daffodil's penchant for destruction by putting them in a seperate vase for at least a few hours to dry out the sap. Then when the water is replaced most of the toxic stuff is washed away. More will leak if you cut or otherwise wound the stems again though.

And you might not want to toss the mucilage at all because some plants actually seem to like it. Irises for example live longer with daffodils. It seems that for them narciclasine prevents the production of enzymes and other proteins involved in aging, allowing the flowers to last longer. And irises might not be the only species to benefit from the daffodil's sap.

The father of medicine, Hippocrates, used salves of Narcissus oil to treat cancer, of all things, way back in the 4th and 5th Century BCE. And narciclasine's anti-tumor potential was recognised when it was isolated in the 1960s. So now researchers are taking a closer look to see if its ability to impede cell growth and survival could make it useful for managing and treating cancers.

So yeah, daffodils are surprisingly feisty and that's part of what makes them great.

-[Stefan] Now if you think those daffodils are hard-core just wait until you hear about giant hogweed. It'll give you third-degree burns with just its sap. Here's Michael with the details:

-[Michael] In the roadsides and ditches of New York State lurks a plant straight out of your worst nightmares. It's a relative of the carrot. But this carrot can grow to be over 4 metres tall and if you're not careful it could send you to the hospital with third-degree burns.

Not only is it dangerous...

 (04:00) to (06:00)

... to humans, it's also really good at crowding out native species. It's called giant hogweed and it's one plant you don't want to mess with.

Giant hogweed is native to the Caucasus Mountains in Western Asia. It was introduced to Europe in the late 19th Century, and to the US early in the 20th Century. These people thought it would look cool in their garden.

It can get really tall, has leaf arrays that are up to 1.5 metres wide and white flower heads that can be as wide as three quarters of a metre across. So yeah, I guess you could say it's pretty remarkable looking, but inevitably it busted out of people's back garden plots and started to grow wild, usually along streams and roadsides.

Todays, it's established in parts of Europe, Southern Canada and the US. It's especially wide spread in New York, but it's been spotted in about a dozen states, including all the way across the country in rainy(?) Washington.

What makes giant hogweed so dangerous is its sap, which can which can get on you if you break the stems, the leaves or even just brush up against the bristles on the stem.

The sap contains organic compounds called furanocoumarins that can penetrate your skin cells, getting right up into the nuclei alongside the cell's DNA. If these compounds are then hit by ultraviolet radiation, you know, like sunlight, they can absorb some of the light's energy and trigger two of the nucleotides in DNA, thymine and cytosine, to form cross-links in your DNA strands that really shouldn't be there. Enough of these unwelcome disruptions and the cells stop working.

Hogweed's relatives actaully produce these nasty compounds too, usually at lower levels, though people have reported burns similar to hogweed from contact with carrots, celery, or parsnips, as well as some citrus fruits and figs that also make furanocoumarins.

And that's because regardless of where they come from you experience this DNA damage as a condition called phytophotodermatitis. That's phyto for plant, photo for light and dermatitis for skin problem.

In response to light your skin turns red and can develop nasty blisters and burns which can last for months. You can also end up with dark patches because your skin tries to compensate for the light-induced damage by producing the pigment melanin to absorb some of the rays.

Even after the initial burns heal, the affected skin can be sensitive to light for years. And if all that's not awful enough, giant hogweed isn't just bad news for us; it can spell trouble for native plant communities too.

 (06:00) to (08:00)

Each plant produces more than 20,000 seeds when it flowers, which is does just once. That's a lot of potential baby hogweed plants.

As they grow, they can form tightly packed stands. And once established giant hogweed lives up to its name: hogging all the resources for itself.

It's huge size and giant leaves allow it to shade(?) out and eventually eliminate it's neighbours. And studies suggest it may even poison neighbouring plants by sending toxins through the soil. If so that means it engages in chemical warfare on multiple fronts, but the evidence is mixed.

Given all this, it may be hard to understand why gardeners brought such a horrific plant around the world in the first place but not all non-native plants becaome giant hogweed level menaces so they probably didn't see all this coming.

Scientists are still figuring out why some non-native plants become invasive, meaning they cause serious harm ecologically, economically or to human health, when others don't.

Giant hogweed has some characteristics that are often considered typical or aggressively invasive plant species, like it produces a lot of seeds and grows really fast. But it lacks others, like that those seeds aren't readily dispersed long distances by birds and such.

Of course no one plant has every characteristic that makes it a good invader, and multiple strategies can lead to success in a new ecosystem.

So by studying species like giant hogweed, researchers can better predict what garden favourites will wreak havoc. In the meantime, if you spot something you think might be a giant hogweed take some photos and send them to your local environmental authorities.

In the US, many states have invasive species task forces for this kind of thing. Or, if nothing else, you can talk to someone at the nearest national or state park or national wildlife refuge. And other countries usually have similar people you can inform. Whatever you do, don't try to get rid of it yourself. really, just don't. Trust us.

-[Stefan] So yeah, I definitely don't want to run into any of those. But even hogweeds are kind of tame compared to the world's most dangerous tree. Here's another one from Michael.

-[Michael] If you're ever vacationing in the flamingo section of Everglade's National Park in Florida, beware of the apples. In fact if you're pretty much anywhere from Northern South America to Florida, including the Caribbean and Galapagos Islands....

 (08:00) to (10:00)

... and you see a tall tree growing near water with yellowish greenish looking crab apple fruit, it's probably bets to keep your distance. The fruit might be delicious but it can also be deadly because that tree might be a manchineel, which according to the folks at Guinness World Records is the world's most dangerous tree. 

Every part of the manchineel is toxic. The sap and its wood and leaves cause blindness and blistering, its fruit can cause boils in the mouth and throat as well as severe intestinal damage that can kill you. It's no wonder Spaniards gave it the nickname "la manzanilla de la muerte", or little apple of death.

The tree contains a number of toxins but the worst is probably phorbol. Or should I saw phorbols. Phorbol refers to a family of related organic molecules that have two terpene chemical groups. And they're similar to compounds you have in your body, which is a bit of a problem.

See, phorbols mimic the action of diaclyglycerol, a fatty molecule your body uses in a number of ways, including to activate an enzyme called protein kinase C, or PKC for short.

PKC is a pretty big deal because it regulates things like cell growth and metabolic activity. So when phorbols over activate PKC, cells will increase their expression of genes involved in inflammation and death. This leads to a range of nasty effects like blistering and ulcering.

Manchineels have phorbols everywhere, which is why you shouldn't touch any part of them.

Oh, and here's a not-so-fun fact: phorbols are very soluble in water so it's not a good idea to stand under a manchineel when it's raining either, which you know, it does in places like the Everglades. A lot.

What's not entirely clear is why this tree went so over kill on the toxicity. It may be that since the manchineel typically grows in areas where there are lots of other toxic plants, it has such overdeveloped defense mechanisms to stay competitive.

And it can get away with having toxic fruit because it doesn't need animals to spread its seeds. It lives by the ocean so it's fruit can bob along on the waves to move to new lands.

Though it may get more love from critters than you'd think. Some reptiles seem to eat the fruit with no ill effects and black spiny-talied iguanas will even live in the trees.

 (10:00) to (12:00)

How remains a mystery.

And even our species doesn't always keep away. Because the trees live in places like Florida, where there are lots of strong winds, and you know, hurricanes every so often, their wood is really hard. So cabinet makers love it, though they have to carefully cut and dry the planks for several days to let the phorbol-laced sap evaporate out.

And the trees aren't just hard. Their deep roots and thick branches help protect coastlines from damaging winds and waves. That means while they may be toxic to touch, they help protect us and coastal ecosystems during storms. So if you do see a manchineel while you're strolling along the beach, you can smile and appreciate all it's doing for the plants, animals and people who live nearby.... and then give it a wide berth.

-[Stefan] Well, no wonder they've got such a bad reputation. Though not every toxic plant deserves its bad rap, like the slightly misunderstood poison ivy.

Nothing can ruin your vacation quite like an encounter with one of nature's purveyors of itchiness. Of course I'm talking about poison oak, poison ivy and poison sumac and their notorious relatives.

Yes, these botanical nightmares are clearly out to make camping and hiking as miserable as possible... but maybe they're not?! Maybe they were just hanging out in the forest enjoying the fresh air and trying to keep harmful microbes at bay until you and your overeager immune system happened to come along.

Poison ivy and the like are innocent. These plants all produce an oily resin called urushiol, and it isn't just in their leaves; it's in every part of them and it remains even after the plant has died.

This urushiol is what causes that notorious itchy rash you get, or what doctors call urushiol-induced contact dermatitis. Now the leaves have to be crushed or somehow damaged in order for the urushiol to actually contact your skin, so you won't get it just by touching the plant.

Of course leaves and such are easily damaged by insects, passing animals or a stiff breeze, so just because you didn't damage teh leaves yourself doesn't meansomething else didn't get there first.

In fact because urushiol causes such a violent rash in people, there's this pervasive idea that the resin evolved as a defense mechanism against large mammals like us...

 (12:00) to (14:00)

But that's not true.

Or at least if it was a defense mechanism, it would be a really lousy one, since urushiol doesn't bother most animals that encounter it, just us and apparently hamsters.

But it has no efffect on the animals that actually feed on the plant, like deer, insects and birds. That's why scientists think it's more likely that urushiol eveolved as an antimicrobial. It's quite effective against much smaller plant pests.

There's even been some speculation that birds that eat the seeds actually benefit from urushiol's antimicrobial and antiparasitic properties. It's simply an unfortunate accident of evolution that makes these plants in compatible with humans, so the rash, oozing blisters and relentless itching, it's all pretty much down to cosmic unfairness.

Urushiol interacts with your skin cells; specifically, ones that express a protein called CD1a. CD1 proteins help the body spot invaders and sick cells. They bind to specific fats, then show those fats to the body's immune cells.

Except human CD1a has the unfortunate tendency to set off attacks in response to things that aren't pathogenic. And it just so happens that urushiol is one of those things.

Urushiol-loaded cells activate the body's T cells, those vigilant warriors of the human immune system. Then the T cells release two proteins called interleukin 17 and interleukin 22, and they're what make you itch.

The redness, swelling and blisters all occur because your immune system harms your skin cells in its attempt to eradicate a bit of harmless oil.

Now of course, this doesn't really apply to those 10-15% who don't seem to be affected by urushiol at all. For some reason nature has seen fit to spare some people from the horrors of urushiol, but there hasn't been a lot of scientific research into why that is. It might be because urushiol-induced contact dermatitis is basically an allergy and allergies occur when the body mistakes a harmless substance for something harmful.

And like with other allergies, some people's immune systems just go haywire when encountering urushiol while others don't. It's just that most people are allergic to urushiol. But also some of the people who say they're immune probably aren't really immune.

Most people don't react to urushiol the first time they're exposed, so a person might believe they're immune when in fact they could go on to develop an allergic reaction....

 (14:00) to (16:00)

... if they touch it again. And even if they've had a couple of exposure with no reaction, they could still develop a sensitivity later in life.

Increased exposure is thought to increase the likelihood of developing sensitivity, so if they roll around in a bunch of poison ivy to show off to their hyper-allergic friends, they might end up experiencing some itchy, itchy karma.

Though wierdly enough, sometimes sensitivity to urushiol fades as people get older. Scientists aren't really sure why, but it might have something to do with the fact that your immune system weakens as you get older. And a weaker immune system may not mounth as strong a defense against urushiol. So, that's one advantage to getting older.

At any rate, whether you think you're immune of not, or may have become less sensitive over time, you probably don't want to push your luck. Urushiol-induced contact dermatitis is miserable at any age, so it's always a good idea to avoid which ever version of poison whatever is in your neighbourhood.

Now, speaking of misunderstood organisms, you often hear people talk about poisonous snakes, and while that's usually wrong, it's not always.

Some species are poisonous and venomous, so double the danger. Here's Hank with more:

-[Hank] If you've ever called snakes poisonous around a herpetologist, you know that friend of yours, you know which one I mean, there's a good chance you'll receive a lecture about the difference between venoms and poisons. And it's true that most snakes aren't considered poisonous but nature loves an exception.

Meet the tiger keelback. They've got the best of both worlds: poison for their predators and venom for their prey.

It can be easy to confuse the terms venom and poison but the difference does actually matter. Both are made up of toxins, biological chemicals that mess with body functions in small amounts. The technical difference has to do with how they get into a victim's body.

Poisons enter passively, by being eaten, breathed in or absorbed through the skin. And because of that, they're usually defensive; an organism's way of saying "Hey don't touch me. You will regret that."

Venoms, on the other hand, are actively injected into the body, like via a pair of pointy snake fangs....

 (16:00) to (18:00)

... for example. Venom can certainly be used defensively, but often, venomous animals are predators that use their toxins offensively, so they can enjoy a meal without all that troublesome struggle.

Sicne venoms and poisons tend to be used differently, they usually contain different kinds of toxins. So a doctor would want to treat a snake poisoning differently than a snake bite, or what's known as envenoming.

And the distinction is particularly important if the snake in question is a tiger keelback. These snakes can be found across South-Eastern Asia and they belong to a huge and diverse family of snakes called the colubridae.

These are sometimes referred to as "rear-fanged" snakes because unlike rattlesnakes or cobras which pump venom forcefully through hollow fangs in the front of their mouths, colubrid fangs sit further back in the jaw and deliver venom along open grooves. They kind of have to chew on their prey a bit to get the venom moving.

Most of the time, tiger keelbacks use their venom to take down tasty fish, tadpoles and their favourite: frogs and toads. They rarely bite humans but when they do, it's not a fantastic experience for the human.

The venom can cause hemorrhaging and mess with blood clotting, leading to excessive internal and extrenal bleeding and in several known cases, death. Thankfully antivenom is usually an effective treatment, if delivered in time.

Now all this talk of killer snake bites might sound scary but it's important to remember snake don't want to bite you. Really they don't. They'd much rather svae their venom for their prey; they don't want to waste it on something they can't eat.

And that may be partly why the tiger keelback usually fends off threats another way. on the back of these snakes' necks are several pairs of nuchal glands. I the right pressure is applied, these glands crack open and spew out a stinky, toxic, yellowish pus.

The poisonous nature of this stuff was first noted in 1935 when a scientist who was dissecting a keelback cut into its nuchal glands accidentally spraying the poison right into his eye. Which is just one of the many stories that science teachers have heard...

 (18:00) to (20:00)

... and why they get so fussy about you wearing your safety goggles.

The poison contains bufadienolides which can cause acute pain and temporary damage to the cornea if they get in your eyes. When ingested or inhaled, they can irritate any tissue they touch and even cause heart problems.

And the snakes know how to use their poison. When confronted with danger, they assume an arched posture and aim their neck towards the threat. Sometimes they'll even swing their neck at an attacker, poison glands first, in a manoeuvre that scientists have delightfully named a "neck butt".

Maybe the most interesting thing about his poison is that they don't make it. They pick it up from the toads they eat.

Research has shown that tiger keelbacks living on toad-free islands don't have these poisons but they can become poisonous if given toxic toads. And you'd think that a lack of poison would be a problem for a new-born snake but it turns out mama keelbacks can pass toxins along to their young.

It's unclear if she adds it to the yolks or just bathes her eggs in the stuff. Experiments have shown that keelback babies absorb toxins through their eggshells. Either way, by the time the baby keelbacks hatch, they are ready to defend themselves.

And here's something super weird: the snakes are more likely to flee from threats than face them neck on if they've been deprived of toads, suggesting the animals somehow know when they're poisonous. Also the snakes don't just take the toad poisons as is and stick them in their glands. They actually modify them chemically to make them even more potent.

The tiger keelback is definitely the most well-known example of a poisonous snake, but it's likely not the only one. Other related species have nuchal glands, they might have poisons of their own that simply haven't been studied.

Research has found that other snakes, like garter snakes, can eat so much poisonous prey their organs become toxic to predators. Since most people don't usually eat snakes, there could be a number of species that would make us sick, that we just don't know about.

So future studies may reveal that the tiger keelback isn't that much of an exception after all. In the mean time you can tell that pedantic friend of yours that there definitely are...

 (20:00) to (22:00)

... poisonous snakes, so bleh.

-[Stefan] See poisonous snakes is correct... at least sometimes. Take that science pedants!

But speaking of pedants, you might've heard that because venoms and poisons are different, venoms are safe to drink. But ummm.... allow me to explain.

If I were to ask you whether it's safe to drink snake venom, you'd probably have a very firm answer right away. Either you'd automatically say no, because snake wield deadly poisons, or if you're a science pedant you might unequivocally say yes, because snakes wield venoms not poisons. Well, I'm here to tell you that, actually, both of those answers are wrong. And at best, the correct answer is maybe?

Let's start with the sure-fire no. The science pedants out there are right when they point out that venoms and poisons differ, namely by the route or administration. Both fall under the broader umbrella of toxins, meaning they cause problems in relatively small amounts.

But venoms get into you via wounds, like a snake bite, while poisons are either inhales, swallowed or absorbed through the skin. And yes this difference matters when it comes to how toxins affect you.

Since venoms go directly into your bloodstream, it doesn't need to be able to survive a trip through your stomach. So venoms often contain big, somewhat delicate molecules that can be inactivated or destroyed by your digestive juices.

But before you run out to do a shot of snake venom, let's move onto the misconception behind that solid yes answer.

See, there may be no evolutionary reason for venom toxins to work when consumed, but that doesn't mean that they never do. What you really need to know is the venom's oral toxicity, how different amounts affect you when injested.

And oral toxicities tend to be lower than injected ones. That's in part because of those digestive juices we mentioned. Also there's the physical barrier of your gut lining, so odds are, some of the stuff just passes through you without getting absorbed.

That doesn't mean venoms are guaranteedly drinkable. For instance the venom of the blue-ringed octopus contains the potent paralytic, tetrodotoxin...

 (22:00) to (24:00)

.. which is roughly 40 times less toxic when swallowed than when injected. But still it's a super deadly poison, so if you did somehow manage to obtain a shot glass full of venom from these golf ball-sized octopuses, you definitely wouldn't want to drink it.

I can't actually say that it would kill you because we haven't tested this venom's oral toxicity but that's kind of the thing. We haven't tested most venoms that way. There simply hasn't really been a reason to. So we don't know if they're safe to drink, though we do have some evidence to suggest that they aren't.

For instance, in a study published in 2015, rats that ingested cobra venom ended up with damage to their livers reminiscent of what happens after a regular bite. Plus, there's been at least one case where someone almost died after drinking snake win, a beverage prepared by steeping an entire venomous snake in alcohol.

And this guy wasn't suffering from run of the mill alcohol poisoning. He was admitted to the hospital because his blood had stopped clotting properly, a symptom often caused by snake venoms. And he got better after receiving anti-venom.

Researchers in Australia are actually hoping some venom toxins work orally, on insects that is, that way they can be more easily used as pesticides. And so far, 70% of the spider venoms they've tested killed the fruit flies that ate them, which sounds promising as far as pesticides go.

Now, that doesn't mean they're dangerous for us to drink but still the research is further evidence that venom toxins can do their nefarious work when ingested.

So, can you drink snake venom? I mean, maybe? It could depend on the species of snake, but we haven't done the tests to find out. And making assumptions based on the difference between venoms and poison is a terrible idea.

Yeah, we al probably should've figured that was a bad idea. But I think we can all agree that nature is amazing, and also kind of dangerous. And the science of toxins is endlessly fascinating.

If you want to dig deeper into how other toxins work, and the cool stuff they do, I am pleased to inform you there is so much more. We have episodes on poisonous house plants, and the deadliest substances on Earth, just to name a couple so...

 (24:00) to (24:18)

... be sure to check those out. And as always: subscribe and ring the bell to keep up with the latest episodes of scishow. Thanks for watching.