Newton's Slime Cannon - EWTS #010

Senan: Welcome to Enough with the Science.

Joe: Hello there, welcome back. Episode two, season two; and it’s all about goo. See what I did there?

Senan: Oh, you’re a poet and you don’t know it.

Joe: There we are. Thanks Senan. I’m Joe.

Senan: Yes and I’m Senan.

Joe: Maybe you know, maybe you don’t know, but this is the show where we talk about science. Senan researches a topic and I try and basically distract him from his ramblings.

Senan: What do you mean I research a topic? Are you suggesting that I don't actually just innately know all this stuff?

Joe: It’s about time you got the respect you deserve for all the hard work you put in.

Senan: Which is zero.

Joe: He’s like a supercomputer. He just knows all these things. It’s like working with an AI. Actually, I only read this week; is it Inception AI? They’ve made a hundred thousand podcasts just using AI voices in the last six months.

Senan: That’s it, we’re finished. Why are we bothering?

Joe: Before we even began; we're finished. But we’re not finished because we’re here for you, the listener. This is all about goo. We’re talking about mucus; we’re talking about... what's your favourite synonym for mucus?

Senan: For goo? Oh, for mucus; probably snot.

Joe: Snot? Snot is a good one. I think gunk. I like gunk. Gunk is a good word. Get rid of that gunk. Gunk all over the place. Where is that gunk coming from?

Senan: Anyway, we’re going to talk about the wonderful world of slime and mucus which turns a lot of people off and actually, there’s a good evolutionary reason for that because often slime or mucus is a defensive mechanism with some unpleasant chemicals in it and we have evolved an aversion to it as a result of that; to stop us from eating things that have unpleasant chemicals in them.

Joe: But not just because it’s disgusting to see somebody picking their nose when they’re sitting in traffic?

Senan: It’s interesting actually to see what technique they involve; there's so many different techniques out there.

Joe: I think the first technique is the fact that people think they’re invisible when they’re in their car. They just think "Oh, nobody can see me. Here I’m going to investigate. Oh look, what I found in my nose." So it is some sort of goo and some gunk that’s in the nose. But...

Senan: Mucus has evolved again and again in separate scenarios throughout the animal and plant kingdom over billions of years. It's a real example of what they call convergent evolution; which is where the same solution to a particular problem in the environment evolves separately in different creatures.

Joe: So essentially, even though you’re going to explain it in greater detail as we go on, gunk is really important.

Senan: In so many ways. So let’s talk about some of the important properties. So obviously adhesive is one very important property. If you’re a snail and you’re crawling up the outside of my bedroom window, you really don’t want to fall off halfway up.

Joe: Yeah. For us though, we would like it to fall off.

Senan: Oh absolutely, we’d like if it never could stick to the window in the first place. Then there’s moisture retention. If you’re a piece of seaweed and the tide goes out, you don’t really want to dry out and die while the tide is gone out; so you need a nice little coating of mucus on your leaves to stop you from drying out.

Senan: A big one is protective barriers. In all kinds of different ways; at the basic level of trying to protect from bacteria. You can have a thick layer of goo between your skin and the bacteria; not suggesting your skin is gooey for a moment Joe. But creatures in general. And the bacteria essentially, it’s like a barrier that physically prevents the bacteria from reaching you; plus also you can then put antimicrobial chemicals in the goo that attacks the bacteria while they’re stuck in it. That’s one thing.

Senan: Another one is your stomach. Your stomach produces quite strong acid that is used for digestion but you don’t really want that acid to actually digest your stomach itself. So your stomach has a nice coating of mucus on it to protect it from its own acid.

Joe: So obviously fundamental to life, I would venture?

Senan: Then of course there’s lubrication which we’re not going to go any further with examples of that one.

Joe: Until later.

Senan: Until later. Until after the nine o'clock watershed when the kids are all gone to bed. And then there's particle trapping. So if you find yourself in a real dusty environment and you’re inhaling that air that’s full of dust; you don’t really want that horrible dust getting down into your lung and causing pneumonia. So you've got mucus inside your nose and inside your throat that is going to trap some of those particles and eventually it means they get expelled.

Joe: So essentially we are mucus making machines.

Senan: In so many ways, so many parts of us. And it's a defense mechanism in other ways too for various other creatures; not so much for us. Obviously there's bacterial and chemical defense for us but other creatures use it to actually actively repel predators. We'll come back to that later; there's one real cool creature called a hagfish. He's like the king of the mucus creatures.

Joe: I bet you it’s a very ugly fish. It sounds like an ugly fish.

Senan: Yeah, possibly isn't going to win any beauty contests. So how is this stuff actually made down at the molecular structure; how does it work its gooey magic?

Joe: Goo. I thought it was just made of goo. Is that not enough? What is it? It's gunk. Get rid of that gunk. Where is goo on the periodic table of elements?

Senan: GE. What's the atomic weight? How many protons, how many electrons? I don't know. Is it perhaps; does it decay into something else like uranium? So anyway, animals have one mechanism for producing it called glycoproteins and plants have a slightly different one called polysaccharides. But the underlying mechanism is similar enough so we'll just talk about the animal one because we don't have all day.

Joe: To go into great detail.

Senan: They're initially produced; the chemicals or things that make up the structure are initially produced without water. When they're exposed to water, they're actually able to absorb, in a matter of seconds, a hundred times their own weight in water. So essentially mucus is effectively trapped water with some other chemicals in there to make it give it certain properties that are desirable. And because the water is trapped at an individual molecular level it can't flow around in the way that normal water can; so that's kind of why it thickens up as it were.

Senan: It started probably with simple sugars. So sugars play a vital role in this. So sugar has the interesting property of being able to attach itself to water molecules. So sugar is one of the important elements that are used in building the backbone of this goo. Before we got proper mucus evolved in the animal kingdom, bacteria had a very basic version of it which we call now biofilms. So essentially bacteria exude a kind of a sugary coating. And when there's lots of them together in a colony, that coating forms like an umbrella or a shield above the colony and it protects them from outside predators, but it also maintains a nice environment; moist and it's got a nice collection of nutrients.

Joe: Probably some background music.

Senan: Potentially, yeah. Maybe a few nice movies on in the corner, that kind of thing.

Joe: Biofilms.

Senan: Exactly. Biofilms. So how is this mucus actually produced in animals? So we've got these wonderful cells called goblet cells. Not goblin cells but goblet cells. And they're called that because when you look at them with a microscope they look like wine goblets. So it's inside in these cellular goblets that the goo is assembled. So you've got a long, an extremely long protein backbone molecule; so this really long single molecule of protein. Attached along the outside of that are chains of sugar molecules. So one end of the chain of the sugar is anchored in this protein backbone and the other end is free to wave around.

Joe: And essentially for different animals, like the goblet cells are the same, or pretty similar in most animals?

Senan: Well I mean in terms of that fundamental structure they're quite similar. But then there's all kinds of other; like some have more slippery mucus than others, some have more sticky mucus than others. So there's little differences and then of course most creatures that produce a mucus will also produce some kind of useful chemicals that are kind of dissolved into the mucus as well. So they're obviously; as I said each animal has kind of evolved its own specialization of the mucus over millions of years.

Joe: But even in one animal, like for example in the human; so you have goblet cells in your nose, you have goblet cells in your lungs. Are they the same essentially?

Senan: Well they're fairly similar those two because they happen to be part of your respiratory system; although in your nose you tend to get a lot of antibodies, you know. When you get a cold that mucus, goo that comes in your nose and sinuses is part of your antibody system that's trying to protect you against the cold or fight it off. So there's probably less of that going on in your lungs, but you still get mucus production in your lungs. But if you look for example at your digestive system, your tummy or your bowels or whatever; there would be goblet cells there but they'd be doing a fairly different process to what's going on in your nose. So you know, even within the one animal there's different kinds of goblet cells.

Senan: So anyway, you get this; the best way of visualizing these long molecules is a bottle brush. So imagine; you know the bottle brush has got this steel wire thing in the middle that runs the length of the brush?

Joe: I'm just trying to imagine what age demographic has stopped understanding what you're talking about. Under 40? Under 30? Under 40, who cleans bottles? Bottle brushes? I don't know, I don't think so.

Senan: Okay, we better go back to bottle brush 101. It's a long thin wire and sticking out of; kind of attached to the wire are nylon bristles that stick out like hedgehog bristles either side of the brush in a kind of a cylinder. So you've got this cylinder of sticky-out nylon bristles with a wire in the middle holding them all together.

Joe: Very good description, yep.

Senan: And you shove that into a bottle with some detergent and water and you scrub like hell to clean the inside of the bottle. Imagine a really long bottle brush; that's kind of what these molecules are like. And because they're so long they're able to tangle up in each other. And that's essentially what holds all this mucus together.

Senan: So we now need to mention something called Daltons.

Joe: Oh no. Was he the character out of Road House? Was that the name? Dalton? Was he the Patrick Swayze? My god, you’re showing your age now.

Joe: The original Road House, not that travesty that was made with McGregor afterwards. No. I think the character's name was Dalton. Sorry. It's not that one.

Senan: This particular Dalton lived in the 1800s; almost two hundred years ago in fact, he was born at the end of the 1700s. He was an English chemist and he was involved in trying to figure out what atoms were made from. Anyway, he came up with this idea for a fundamental unit of measurement for the mass, or essentially the weight I suppose you'd call it, of an atom. And it's roughly; so one Dalton is more or less what we now regard as the weight of one proton.

Joe: And did he name it after himself? Or was it after he... said "He's done a lot of work let's call it after him"? Or did he go "No, this is mine"?

Senan: Not quite sure what level of narcissism he had so; mine, this is mine! Anyway, he'd be I'm sure chuffed to know that we're still using it. So the average; you know animals, us included, have millions of different kinds of proteins. That's effectively what we're made of in our bodies. The average protein is about 50,000 Daltons in size; so about 50,000 times the size of one proton. That's the individual protein molecule.

Joe: So hold on. A proton is one Dalton?

Senan: Roughly speaking, yes.

Joe: A proton. Not a protein.

Senan: A proton.

Joe: Okay.

Senan: So the average protein molecule that's in an animal like us is roughly 50,000 Daltons, right? These long chain proteins that are in mucus; they're called mucins by the way.

Joe: That's going to come up in a pub quiz. You're going to need that someday. That piece of information is going to save you someday, listeners. Mucins.

Senan: This real long bottle brush molecule is around about 20 million Daltons. So it's 400 times bigger than your average protein. So these are real long strings.

Joe: These are the bullies. These are the protein bullies of the schoolyard.

Senan: Yeah but they're long. It's not a bunch; it's not a round bunch of stuff, it's like a long chain.

Joe: Skinny bullies.

Senan: But and that's how they can tangle up with each other because they're so long. And that's how the mucus all stays together in one blob of goo rather than flowing away like water. So a good way to visualize it is a bowl of cooked spaghetti; the way it's all tangled up together.

Senan: And they have a vast; as I mentioned earlier, when they're still inside the goblet cell they're in an environment where there's almost no water. When they leave that cell and are exposed to a moisture environment, they expand by about a hundred times their original size. That's how much water they're able to absorb. It's pretty phenomenal.

Joe: They're just really, really good sponges.

Senan: And a lot of mucus has a very interesting non-Newtonian property.

Joe: How many rabbit holes do we need to go down for me to explain what that phrase means? Non-Newtonian? Okay, we have to explain what is Newtonian first and then non-Newtonian.

Senan: Well Isaac Newton of course was the father of physics, or at least he was for a long time before the likes of Einstein came along and put the cat among the pigeons. So he came up with theories that described an awful lot about how the world behaves. And so a Newtonian fluid is like how we think of most fluids like water or milk or something. It's splashy, it flows.

Joe: Did he use that word? "Water is splashy." Give him the Nobel Prize for science! Water is splashy.

Senan: He won prizes for this.

Joe: Yeah. Well that's only a very small part of his contribution to science.

Senan: Anyway. A non-Newtonian fluid; so there's a well known non-Newtonian fluid i.e. a fluid that does not behave the way most fluids behave, and that is a mixture of cornstarch and water. So there's umpteen videos on YouTube where you can see people experimenting with cornstarch water.

Joe: Or you could if you had nothing to do with your life.

Senan: And they've even invented a name for it; I think it's Oobleck or something they call that liquid. But it's just cornstarch and water. So it's flour essentially; flour and water. Cornflour. It's something to do with the starch in the corn that causes what I'm about to describe next.

Senan: So if you take your finger and you gently scoop it through a bowl of this stuff; you know, your finger moves through it like you would expect and then there'd be a covering of it on your finger when you take a finger out, a bit like say custard, right? But if you ball up your fist and you punch it hard, it's going to feel like punching a solid object. So the fluid is going to momentarily solidify when you apply a sudden force to it by punching it with your fist.

Joe: Now, I'm still not convinced that you're not just winding me up and I'll go home and break my hand in a bowl of cornstarch water.

Senan: I'm going to leave that with you. You're just going to have to make that decision.

Joe: This is non-Newtonian! I'll be screaming in the ambulance on the way to the hospital. "Non-Newtonian he said!"

Senan: So the weird thing about mucus is it's non-Newtonian in the opposite way to cornstarch and water.

Joe: Oh it's reverse non-Newtonian. Oh well why didn't you say so? That's easy.

Senan: So when it's not under pressure; you know when it's just sitting there, it's quite sticky and gooey, right? But when you move it quickly, it becomes slippery and lubricant. So it's weird; it gives it this dual property of being sticky and thick when it's just sitting there not doing anything, but when you want to use it as a lubricant and you want to move, the actual action of the movement is what makes it momentarily get slippery again. So that's like the opposite of what's going on with the cornstarch and water. So that's a very important property of it.

Senan: Let's talk about how some of the ways it's used for defense. So as I mentioned earlier bacteria can get trapped in it and they won't reach your skin but then chemicals that were produced in the mucus will then attack the bacteria and kill them while they're trapped in it. So that's one thing.

Senan: But I also mentioned earlier a critter called a hagfish.

Joe: Is it the ugly one?

Senan: No, they're beautiful. I'm sure their mothers think they're beautiful anyway. This is a deep ocean fish; resembles an eel but isn't actually a true eel, it is a different kind of fish but looks; it's a long thin thing that looks like an eel. Now sharks like to eat them if they can. Sharks are one of the major predators of these guys. But they have a trick up their sleeves. Like these; let's look at the size first of all. This fish is typically about 50 to 70 centimeters long. So somewhere between a foot and two feet in length.

Senan: And if a shark attacks it, within a matter of seconds goblet cells all over its skin will release up to 20 liters of slime. Now for a fish that's less than two feet long, 20 liters is an awful lot of slime to be released in a matter of moments. And it's particularly thick, gooey, stringy; remember we're underwater here so there's no point in releasing mucus that's just going to dissolve away in the water. So this stuff is really thick, gooey and it clogs the gills of the shark that's trying to eat; plus fills his mouth with this sticky goo as well but it finds its way into the shark's gills and sharks can suffocate from it, or at the very least they can have difficulty breathing and it's enough to repel the shark and they'll go away and leave the hagfish alone.

Senan: The really interesting thing at the molecular level is that the protein threads, the bottle brushes that we spoke about earlier; from hagfish, they're a hundred thousand times longer than the bottle brushes that you or I make in the slime in our mouths.

Joe: We're feeling kind of inadequate as bottle brush manufacturers.

Senan: Yeah so these hagfish, they're like the kings of slime. And then you've got ones that actually weaponize it. So these are the velvet worms. And these guys actually use slime for hunting. So you're talking about a worm that's only a couple of inches, like maybe four or five centimeters long, small little creature. And they're able to shoot slime out of; they have a gland that we'll call a slime cannon.

Joe: [Laughter] There's going to be a superhero out of this. There's got to be a superhero.

Senan: Yeah imagine he could have a velvet cape and velvet skin-tight pants.

Joe: A slime cannon. All he needs is a slime cannon. He wears what he wants. If he's got a slime cannon...

Senan: And he has slime cannons on his shoulders. Anyway, these guys can shoot this stuff out 30 centimeters which in itself is a bit of a wonder. And they don't just shoot it out in a straight line; they're able to oscillate the slime cannon backwards and forwards like several times a second, so they shoot it out in a kind of a cone of spray. And it travels at five meters a second which is pretty bloody fast for a small little creature like that.

Senan: But its real strength is what happens after it gets sprayed out. So they're using it to try and catch something they want to eat. So when it's getting sprayed out, it's a nice flowy liquid; it's able to spray out in a nice fine spray. But the mechanical, the sudden mechanical jolt that's caused by it being shot out of the cannon at such a fast speed causes an actual change in the properties of the proteins that are in it and it becomes semi-solid in mid-air as it's traveling towards the predator or the prey.

Joe: Is this reverse non-Newtonian stuff again?

Senan: Yeah there's something like that going on. But so when it hits the prey, it's like this sticky spider's web has landed on them. It's a solid web of stuff and they just get all tangled up in it.

Joe: What is the prey? Like water buffalo or kind of a hippo?

Senan: I think it's reindeer and polar bears.

Joe: Reindeer and polar bears.

Senan: But yeah, so it's weird the way some of these things work when you get into the kind of low-level molecular stuff.

Joe: Well I know I mean we have several regular listeners in the Department of Defense whose ears pricked up once you said "weaponize." I'm sure people must be examining these properties and kind of going "How can we weaponize that?"

Senan: Deploy the slime cannon.

Joe: Slime cannon. Someone is probably patenting that as we speak.

Senan: Right. We need to talk about the brainy mucus.

Joe: Is there brainy mucus?

Senan: Well there's a mucus that kind of has some kind of intelligence associated with it and this is slime molds. So they're a single cell creature and even the way they move, which has nothing to do with slime, is interesting because they move really, really slowly but how they do it is the external membrane of this single-celled creature is kind of flexible and they're able to vary, increase and decrease, the pressure of the liquid inside in the cell contained inside the membrane; their internal body as it were is mostly liquid. And they're actually able to pump or compress that to increase its pressure briefly and then release it again. So they go through these pulses of increasing, releasing, increasing, releasing pressure and it essentially squeezes their flexible membrane in the direction they want to go in. So that's kind of how they move which is cool enough before we even get into the slime.

Senan: But they do release this slime trail a bit like a snail behind them as they're going along. And there are biochemicals in that which they're able to detect if they pass over it again. So they know where they've been already and if they're exploring a new area looking for nutrients or whatever else it is that slime molds are looking for, they know where they've been already so they can efficiently explore an area without doubling over.

Senan: But the really interesting part is that the slime trails they leave on the ground behind them are actually able to conduct some tiny amounts of electricity; it's known as an ion channel. And they're actually able to use that as a kind of a very rudimentary form of thought. So it's to do; they can send signals back through the slime trail from one part of the cell to another. So if the cell is lying on different parts of the slime trail, the signals can go over and back through the trail. And this actually assists with their ability to navigate efficiently to find whatever they're looking for. And like they've done experiments, experiments have been done in laboratories where they've made these things go through mazes, where maybe the exit from the maze has some nutrients they need or whatever, and they're actually able to navigate through mazes really efficiently using a combination of the fact that they can detect their own slime trail and this chemical or electrical signaling that goes on in the trail. It's weird.

Joe: So essentially when they go into the maze, or anywhere out in the open, they can head off and find a dead end and then return and then head off and find another dead end and come back; but the ion trail will let them know that they've been down that way before and they don't need to go there again?

Senan: Yeah, yeah. So they don't have anything like a brain or consciousness but yet there is some kind of rudimentary intelligence going on there that's utilizing that electrical current through the trail, yeah.

Joe: But this is a single cell that is visible?

Senan: I think; I'm not sure of the scale of them but I think possibly they might be visible. Because if you look there are videos online of them actually; that pulsing I spoke about earlier for how they move, they have you can take a video and then speed it up because normally the pulsing is so slow we wouldn't notice it and so they must be reasonably big if there's videos of it, you know?

Joe: And also you don't really want to get mixed up between a mucus mold and a jelly mold.

Senan: [Laughter] Very different things. You do not. They're also spelled differently I think.

Senan: Anyway, we would be remiss without mentioning of course one of the very important functions involving mucus and that is reproduction.

Joe: Here we go. This is it. Children, time for bed. Go get a full fat Coca-Cola.

Senan: Yeah or go and look at SpongeBob or something. No, on second thoughts don't go and look at SpongeBob.

Joe: Anyway.

Senan: So female mammals have something called a cervix which is involved with reproduction and there is mucus produced by that called cervical mucus. In sperm there's quite a lot of abnormal, physically abnormal sperm; like they're not nice and straight and streamlined, they're maybe bent or they've got two tails or two heads or whatever. So the cervical mucus is like at the microscopic level is like a mesh net and the holes in the net are only big enough to allow the nice straight streamlined sperm to get through. So that filters out 99% of the abnormal, of the physically abnormal sperm to stop them from trying to fertilize an egg.

Joe: Quality control.

Senan: Exactly, quality control. But there's also the constituents of the mucus changes depending on what part of the woman's ovulation cycle is, you know what time of the month it is effectively. Because there are certain periods during the ovulation cycle where it's the best time to conceive; it's most likely to conceive. And the mucus becomes more friendly to sperm; it's a nicer environment for sperm to swim through and it's easier physically for the sperm to swim through it at those times in the woman's cycle.

Senan: And then there's the whole pheromone part of it. So pheromones are essentially chemicals that we can detect unconsciously by with our sense of smell; we're not conscious of them but they do have an action in the subconscious part of our brain. So at the right time in a woman's monthly cycle the pheromones change to make that woman more attractive to males. So it's a really interesting use of mucus that has so many other functions as well.

Senan: And then we could talk about, seeing as we're on the reproduction front, we might as well talk about plants.

Joe: That's a hell of a segue.

Senan: Plants; gardening. Plant reproduction.

Joe: So plants, just like animals, like to propagate the species onto the next generation.

Senan: Seeds. Some seeds have a coating of sticky mucus. So when an animal passes by it sticks to the coat of the animal; the animal walks off and then later on that day maybe the mucus dries out a bit and it's not sticky anymore and the seed falls off and that seed is dispersed to a different place. Then there's a lot of seeds of course like to be moist for germination; while they're going through the germination stage they can't dry out. And some of them have this nice coating of mucus on the outside to keep them moist while they're germinating. Chia seeds are an extreme example of that. Some of our listeners, I know you aren't cause you're a very conservative eater but some of our listeners might observe what happens to chia seeds and the mucus that protects them.

Senan: If you dump a spoonful of them into a glass of water and wait a couple of minutes you'll see they've suddenly; they've turned into nearly frog spawn, there's so much goo on the outside of them.

Joe: And what do you do with that then? Do you drink it? Or is this just an experiment?

Senan: Well that's part of the reason why people eat them because they're very high in insoluble fiber which is good for your digestion. And that mucus is effectively the insoluble fiber that they're high in.

Joe: This program is sponsored by chia seeds.

Senan: And of course then you've got; moving away from reproduction but staying with plants, see what a good segue that was.

Joe: That's another little segue. You realize if they're good segues we shouldn't need to point them out.

Senan: Well you know we have to kind of train our listeners you know. There are certain procedures we need to make our listeners familiar with.

Joe: It's so seldom we get a good segue we need to advertise it. We need to advertise it when there's a good one.

Senan: Carnivorous plants.

Joe: Oh yes.

Senan: So sundews of course are; they look like sticky dandelion seeds. They've got all these little spikes I suppose with little droplets of goo on top of them. And they, you know, a fly likes the smell; there's some chemical the plant exudes that's in that goo that's on the spikes and it attracts flies. They think it smells nice and they land on it; they immediately get stuck. And then there's digestive enzymes in the goo they've just landed on and it slowly digests them alive.

Joe: Oh god. From the legs up.

Senan: For the benefit of the plant. Well they start struggling and of course before long it's all over their bodies as well and from every direction.

Joe: That doesn't make it any better.

Senan: And a related plant of course is the Venus flytrap plant which is a bit more active cause when a fly lands on it, it claps shut on top of it. But there is goo in that one as well that helps to digest the fly. So there's so many different compounds and properties that mucus is used for by different creatures. It's like mind-boggling and it's also so important to life on earth; despite how disgusting we find it otherwise.

Senan: I'm going to mention one last one before we go. And it's an insect this time; we haven't spoken about insects yet. Spitfire sawfly larvae.

Joe: [Laughter] The name alone is enough. We don't have to say anymore.

Senan: That's it. We'll just leave that with you. Look it up. So yeah, so they eat plants and the plants they eat contain small amounts of toxins that doesn't really affect, doesn't poison the spitfly. But they're able to collect those toxins in a little reservoir in their body and as they eat more and more of these plants they build up quite a concentration of these toxins in this little tank they have inside in their body. And then they're able to mix it with a foam mucus that they produce themselves. And a bit like our friends the velvet worms earlier on, they have a mucus cannon and when something threatens to eat them they spray this now quite toxic goo into the eyes or into the mouth of whatever it is that's trying to eat them and it repels them.

Joe: So essentially they're producing poison from plants inside themselves?

Senan: Yeah. Instead of having to go to the trouble of producing it themselves, they just piggyback on this poison that's available from plants they eat and concentrate it within themselves and then fire it at predators.

Joe: I wonder is it one plant? Or is it like, "No I need two of those leaves and one of them and half one of them"?

Senan: Yeah good question. We're getting beyond my level of knowledge now.

Joe: I would imagine it's one plant.

Senan: So on that note now that we have reached the limits of my knowledge I think it's probably a good time to end this episode.

Joe: Gunk. The gunk episode is finished. We actually made it through.

Senan: Yes, we're sticky and we're slippery.

Joe: It's just because it is so disgusting and you go "gunk" and kids go "Yay gunk" and goo and slime and all of those things and but it is interesting that we really wouldn't be here without it.

Senan: Without it. And of course the fact that we find it disgusting is all part of evolution too because we find, it's a lot of the things we might want to eat; if they have unpleasant goo on them that probably is toxic to us or poisonous to us or something we don't really want to eat. And we have evolved to dislike it because that's a way of us avoiding eating something we shouldn't be eating.

Joe: But how have we evolved to despise people who pick their nose?

Senan: Well I suppose we see parallels.

Joe: That's not evolution, that's cultural.

Senan: Cultural evolution we call that.

Joe: Cultural evolution. Not evolution evolution.

Senan: There's essentially two kinds of people on the planet. The ones who pick their nose in public and the rest of us who do it privately.

Joe: Or get away with it. The rest of us who get away with it. Well that's it for another episode of Enough with the Science.

Senan: Yes I'm Senan and don't forget to like and subscribe. You'll get sick of hearing me saying that.

Joe: No, no. We need likes, subscriptions and large bags of money.

Senan: In brown envelopes; this is Ireland. Historically and traditionally it's brown envelopes here in this country.

Joe: And try chia seeds. The best seeds for that stuff he was talking about.

Senan: And don't forget to punch a bowl of cornstarch while you're at it.

Joe: Okay, see you next week. Good luck.