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Tiny Matters
Take a dive into the genes, microbes, molecules and other tiny things that have a big impact on our world with Tiny Matters. Join scientists Sam Jones and Deboki Chakravarti as they take apart complex and contentious topics in science and help rebuild your understanding. From deadly diseases to ancient sewers to forensic toxicology, Sam and Deboki embrace the awe and messiness of science and its place in the past, present, and future. Tiny Matters releases new episodes every Wednesday and is brought to you by the American Chemical Society, a non-profit scientific organization advancing chemistry and connecting the broader scientific community. Tiny Matters is produced by Multitude.
Tiny Matters
[BONUS] A shark’s ‘jelly-filled canals’ and deadly cyanide in clovers: Tiny Show and Tell Us #8
In this episode of Tiny Show and Tell Us, we talk about the ampullae of Lorenzini that allow sharks to detect the electrochemical signals coming from prey. We also cover the fascinating science behind cyanide-filled clovers. Did you know cyanide is actually a very popular poison in the plant kingdom?
We need your stories — they're what make these bonus episodes possible! Write in to tinymatters@acs.org *or fill out this form* with your favorite science fact or science news story for a chance to be featured in a future episode and win a Tiny Matters mug!
A transcript and references for this episode can be found at acs.org/tinymatters.
Welcome to Tiny Show and Tell Us, the bonus series, where you write in with your favorite science story, fact or piece of news and we read your email aloud and then dive deeper. I'm Sam Jones, I'm the exec producer of Tiny Matters and I want to give a big thank you to science writer and chemist Anne Hilden for doing the research for this episode. Today I'm here again with science communicator George Zaidan, who you can also hear on Tiny Show and Tell Us, episodes six and seven. Hey, george.
Speaker 2:Hey, sam, it's great to be here. Before we get into things, just a reminder that Tiny Matters is always looking for you to write in, because that's what makes future episodes possible. You can email tinymatters at acsorg, or you can also click the Google form link that we put in the episode description. So I think I went last time. You want to go first this time? Episode description. So I think I went last time. You want to go first this time?
Speaker 1:Absolutely Okay, so I have a very fun one for you today, George.
Speaker 2:Excellent.
Speaker 1:This is from listener Ian, and Ian writes maybe this is an esoteric and subjective fact, but one of the best named parts of animal anatomy are the ampullae of Lorenzini. Tell me that's not fun to say.
Speaker 2:That's great Ampullae of Lorenzini, named by Italian scientist Guillermo del Lorenzini.
Speaker 1:You're close, I will get into it?
Speaker 2:I really no.
Speaker 1:I mean the like fact that it's an Italian scientist, meaning you're close. Yeah, that was it. That was it really. Ian continues these are the pits in the snout of a shark that are an important part of their electrical field sensory system. Bonus fact these electrosensitive organs were mostly lost during teleost fish evolution, but a few lineages independently re-evolved their spidey senses. Bonus bonus fact, ian, I love these. The ampullae cells are developmentally related to the fluid-sensing hair cells found in fish lateral lines and human ears.
Speaker 2:Oh.
Speaker 1:And one of the genes that's important for both hair cell development and ampullary organ development and may be involved in evolutionary loss gain of these organs. But the details are still. Tbd and messy is the same gene that controls how curved your ribs are. What Evolution's crazy.
Speaker 2:It is wild.
Speaker 1:Ian didn't say that last part, but I think he would agree. Okay, so thank you, ian. I'm excited to talk about this.
Speaker 2:Great set of facts, Ian.
Speaker 1:Yeah, really, really excellent. So Ian did a lot of the research for this and she said that when she first typed ampoula into her search bar, the first word ampoules came up, and apparently in ancient Rome an ampoule was a small round vessel for storing liquid. So it makes sense that, as an anatomical term, ampoules refers to tiny fluid-filled chambers. So let's talk about the ampoules of Lorenzini. They're named after the physician and ichthyologist. That word physician and ichthyologist that word physician and ichthyologist, aka fish researcher, stefano Lorenzini. Love it, not Guillermo Stefano.
Speaker 2:I was so close.
Speaker 1:So close, who gave them an exact description, but he had no idea what their purpose was. So he's like it's these things, they do this thing. Let's name it after me. Slap my name on it, let's go. Let's name it after me. Slap my name on it, let's go. And that was in, I think, the 1600s. Took a while, but fortunately now we know what they do. So these are electrosensory organs that contain specialized cells that can detect small changes in environmental voltage gradients.
Speaker 2:Oh.
Speaker 1:Using ion channels that are molecularly different from those that you see in mammals. Ok, so these are very unique, and so they form a series of tube-like structures just beneath the skin, and I've also seen them referred to as jelly-filled canals.
Speaker 2:Oh gross.
Speaker 1:And one of the oh this is so bad. And one of the scientific book chapters that I perused said quote squeeze the snout. Thick fluid emerges from the ampoules through pores in the skin and I'm like leave that shark alone. Anyway, that's lovely. So these special organs may help sharks find prey, since living creatures generate tiny electrical fields?
Speaker 2:I see I was going to ask, yeah.
Speaker 1:They're able to sense these electrical fields coming off of different things that they want to eat.
Speaker 2:Interesting.
Speaker 1:So the ampullae of Lorenzini have been found not just in sharks, but rays, sturgeons, aquatic salamanders and a bunch of other species. Huh yeah. So researchers have found that electroreceptor systems were present in a variety of ancient fish early on in their evolutionary history. So it seems like some of the groups of fish lost their ability to sense electric fields as they evolved. So this is the more ancient state is like having this capacity.
Speaker 1:So, specifically, the loss happened when teleosts, which are a subclass of bony fish, branched off from sturgeons and paddlefishes, and so most of the fish that we know today are teleosts. And then, similarly, the precursors to mammals actually lost their ampullae of Lorenzini when terrestrial tetrapods branched off from amphibians.
Speaker 2:Interesting.
Speaker 1:Man can't believe we lost those.
Speaker 2:What if people who have sixth sense are really just have the ampullae de Lorenzini?
Speaker 1:Oh, I see a new movie in the works.
Speaker 2:I see dead people.
Speaker 1:No, really, I'm just sensing they're just like growing up and they're just like you.
Speaker 2:Don't have these jelly filled canals like I do oh, that that's actually like a good premise for a horror movie like can you imagine a small child ghost with like jelly coming out right under her eyes?
Speaker 1:awful and then she turns into a shark and it's like sharknado the sharknadoing, or something tonight's dreams brought to you by sam jones oh my gosh, okay, so where was I All right? So sharks and rays. On the other hand, they're cartilaginous fish and they all have ampoules, but both bony and cartilaginous fish of all types have a related system for sensing pressure changes in their environment, and this is called the lateral line system, which I think a lot of people have heard of. Have you heard about this?
Speaker 2:people have heard of have you?
Speaker 1:heard about this? Never. I have never heard of this. Okay, I don't, I'm a dork, okay, so, since it consists so it consists of a line of pores that run down either side of the fish's spine and then they have more pores around their face. The sensory cells at the bottom of these pores have cilia, or hair-like structures that create neural signals according to the movement of fluid in the canal. It's really cool, I would say. Generally, aquatic creatures have all of these like really cool adaptations for sensing their environment.
Speaker 2:Yeah.
Speaker 1:We do not have.
Speaker 2:No, we don't.
Speaker 1:Yeah.
Speaker 2:They live in 3D, we live in 2D, basically.
Speaker 1:Yeah, that's a good point.
Speaker 2:We can't go up when we feel like it. We have to take the stairs or something. Yeah.
Speaker 1:No, that's true. So in this paper that Anne found, which side note was actually published by scientists that I worked with over a decade ago before I started- my PhD because science is so, so small.
Speaker 2:That's cool.
Speaker 1:Yeah, so it says that in fish that have electrosensing cells, those cells develop from lateral line cells while the fish are embryos. So it also says that electroreception has independently evolved at least twice within teleosts, although electroreceptors and teleosts are shaped really differently and may have more active uses like communicating with members of the same species. So pretty cool.
Speaker 2:Super cool.
Speaker 1:Fish are great Mammals. We've got some work to do. Humans. I really am talking about humans, yeah, yeah.
Speaker 2:Some mammals are awesome. Dogs are great.
Speaker 1:That's true. We already established that a couple episodes ago, so dogs are great.
Speaker 2:That might be my favorite one so far is that dogs love you. But of course it would be.
Speaker 1:Yeah, yeah, we're biased.
Speaker 2:We're biased, so I have a fact about clovers from Clover, so we checked on this. It's a listener named Clover, hi Clover.
Speaker 1:Hi Clover and.
Speaker 2:Clover writes in a fact about white clovers and they write white clovers. Trifolium repens are easily identifiable by white stripes on their leaves. Those stripes contain cyanide in them that the clovers release when the leaves are damaged as a defense mechanism. And Clover ends with an exclamation mark which I think is very appropriate given the awesomeness of that short but sweet fun fact. So yes, I want to start with the obvious fact that four leaf clovers are scientifically proven to confer luck on people, so I don't know why this is still disputed. It's obviously true.
Speaker 2:And just moving on from.
Speaker 1:There.
Speaker 2:But seriously, though, when you think of a four-leaf clover, you are probably thinking of this exact species white clovers. If you go on Wikipedia and find the page for four-leaf clover, you will see a Trifolium repens four-leaf clover. Okay, now to the real meat of the fact, which is plants make cyanide, which is fascinating. And it's not just white clovers 2,000 plus species of plants produce cyanide.
Speaker 1:Whoa, okay, that's shocking to me and you know I love talking about poisons. I don't know if you remember that.
Speaker 2:I have been a tiny matters listener for a while, so I am aware.
Speaker 1:How did I miss this? Okay, all right, please continue.
Speaker 2:So, as you probably know, cyanide is toxic because what it does is it interferes with cellular respiration and, to make a really long story short, it prevents your cells from using oxygen, even if you are breathing in all the oxygen that you theoretically would need. And the analogy I like to make here is that it's as if you are dying of thirst in a pool. There's water all around you, but you cannot drink it, so you die of thirst. Cyanide is very toxic. So I weigh about 170 pounds. Half a gram of cyanide is plenty, like more than enough to kill me.
Speaker 2:So two questions One, why do plants produce cyanide? And two, the more interesting question is how do they produce it without also poisoning themselves? So let's, we'll start with the why and then we'll get to the how. So the why is that? We're not 100% sure because we can't ask a plant, but most scientists think that they do it as a defense mechanism, and the reason is that plants can't run away Like if something's trying to eat a plant. It has two options it can do a mechanical defense, like a thorn, or it can do a chemical defense, like cyanide. Another reason they produce cyanide in particular, we think, is because metabolically it's pretty cheap. It's a carbon triple bonded to a nitrogen, and that moiety can either be bonded to a hydrogen or something like sodium or potassium, so it's three atoms. It's easy for a plant to produce and it is toxic to a wide range of living things. So you produce this one poison and you're likely to hit most of the things that would try and come by and eat you.
Speaker 2:Okay, so now the how? How do they make this poison without also poisoning themselves? And this is totally genius. So what they do is they do not produce cyanide by itself, because if they were to, they would poison their own mitochondria. What they do is they attach the cyanide to something harmless like a sugar. So now you have a sugar that is covalently bonded to a cyanide molecule, and this combo molecule, which is called a cyanogenic glycoside, is totally non-toxic because the sugar is so big that it prevents the cyanide from doing what it would otherwise do, and they're bonded together. So that's it. That bond is not going anywhere.
Speaker 1:So can I ask a question, and maybe you're going to get into this Please. So if I ate clover would I get cyanide Like would I experience cyanide poisoning?
Speaker 2:What a great question and the perfect segue into the next. So, yes, you would. And here's why Because the clover and all the plants that make cyanide also make an enzyme that cleaves the bond between the cyanide and the sugar, cuts that bond, that releases the cyanide, and at that point that cyanide can be poisonous and is poisonous. And so when a clover is just sitting around, the enzyme and the cyanogenic glycoside don't ever come into contact with each other. But if you were to chew it, breaking up the cells, smashing all the vesicles inside, mixing all the components, they do come together and that's when the enzyme breaks the bond, cyanide is released, and by that point it's in your stomach, it's in your intestine, it's inside you. It's going to be toxic. So that is total genius.
Speaker 1:There must be so many fictional novels back in from like the 1800s, where these I I want to say women, because I feel like it's like a little bit more stealth, smarter. So I might say yep um, and so I wonder, like how many stories there are of some female character collecting clovers to poison her terrible husband or whatever?
Speaker 2:so actually that's a that's a great point. I didn't look into how much cyanide clovers particularly produce, but there are definitely plants that produce enough where if you eat it as a human, it's going to be toxic to you. There are some species of yucca I think it's yucca that produce enough cyanide that you have to. You have to process the thing before you eat it and, again, the way that you would do that is by simulating chewing. So what people do is that they grate I think it's cassava actually. They grate the cassava and that causes the cyanogenic glycoside to mix with the enzyme and then they just leave it out to dry. Cyanide all evaporates away, or they wash it with water, or maybe they do both, and at that point you have a safe to eat food that has been rid of most of the cyanide.
Speaker 2:And what I really found interesting about this is that I think we've heard often that evolution is this sort of cat and mouse game, and this is a perfect example of this. Like there are some animals that have evolved anti-cyanide defenses so they can eat basically as much cyanide containing plants as they want, and this leads to what ecologists call the Red Queen hypothesis, which is the idea that species need to constantly evolve defenses and counter defenses and counter counter defenses just to avoid going extinct. And the reason it's called the Red Queen hypothesis is that it's from Lewis Carroll's Through the Looking Glass. So the Red Queen says to Alice here you see, it takes all the running you can do to keep in the same place. So you evolve these defenses and counter defenses and counter defenses and counter, counter counter defenses and you end up the like reward you get for that is just not surviving, yeah exactly so I thought that was awesome.
Speaker 2:Thank you, Clover, for sending in a fact very appropriately about clovers.
Speaker 1:Yeah, I love that Also, like when you were talking about the cassava and people grating it, leaving it out. You have the cyanide that actually just vaporizes. It made me think a lot about the number of people that died just trying to eat something. And then they're like well, we can't do it like that. What about if we roast it? Nope, that person still died and the cassava is like got them, just keep going. And then it's like all right, we found a thing. And everyone's like do we have to try a new food? Yes, we have to try a new food. Who's up for it?
Speaker 2:Yeah, and I mean, the really interesting thing about the cassava thing is that you'd think like, well, why do people even grow this? What's the point of growing a toxic food? The answer is that you can grow it, leave it in the ground Animals can't steal it from you because it's toxic and then if you ever have a famine or you're short on food one week, you can harvest some and boom, you can process it and eat it and it's like a safety food. Yeah, that's one way that people use it.
Speaker 1:Oh, that's really cool. Didn't know that Interesting you learn so much in a tiny show on TELUS.
Speaker 2:You do.
Speaker 1:It's really the gift that keeps giving.
Speaker 2:It is, and we learn so much.
Speaker 1:Yeah.
Speaker 2:How much of this did we not know before we started?
Speaker 1:Almost all.
Speaker 2:Yes.
Speaker 1:I knew what a lateral line was.
Speaker 2:I didn't.
Speaker 1:All right, so all.
Speaker 2:All right. Well, thank you for tuning in to A Tiny Show and Tell Us a bonus episode from Tiny Matters, a production of the American Chemical Society.
Speaker 1:To be featured in a future episode. Send us an email with your tiny show and tell at tinymattersatacsorg, or click the Google form link in this episode's description. We'll see you next time.
