SciShow Tangents - Shells

Episode Date: July 11, 2023

From eggs to tacos to Ninja Turtles, some of the best things in life come in shells. So cozy on up inside the nearest conch as we regale you with tales of shells from all across the scientific spectrum!SciShow Tangents is on YouTube! Go to www.youtube.com/scishowtangents to check out this episode with the added bonus of seeing our faces! Head to www.patreon.com/SciShowTangents to find out how you can help support SciShow Tangents, and see all the cool perks you’ll get in return, like bonus episodes and a monthly newsletter!And go to https://store.dftba.com/collections/scishow-tangents to buy your very own, genuine SciShow Tangents sticker!Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! While you're at it, check out the Tangents crew on Twitter: Ceri: @ceriley Sam: @im_sam_schultz Hank: @hankgreen[Trivia Question]Golden ratio nautilus shellshttps://link.springer.com/article/10.1007/s00004-018-0419-3[Fact Off]Batteries made from crab shells https://www.cell.com/matter/fulltext/S2590-2385(22)00414-3https://www.sciencedaily.com/releases/2022/09/220901135827.htmhttps://www.thedailybeast.com/the-future-of-renewable-energy-may-be-this-battery-made-from-crab-shellshttps://www.sciencedirect.com/topics/engineering/cycle-lifehttps://www.acs.org/pressroom/presspacs/2023/march/crab-shells-could-help-power-the-next-generation-of-rechargeable-batteries.htmlMicroplastics and hermit crab shellshttps://oceanographicmagazine.com/news/hermit-crab-behaviour-affected-by-microplastics/https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0030https://pubmed.ncbi.nlm.nih.gov/32343937/[Ask the Science Couch]Mollusk shell development & secretion into spiral shapeshttps://www.scientificamerican.com/article/how-seashells-take-shape/https://www.scientificamerican.com/article/how-are-seashells-created/https://link.springer.com/article/10.1007/s10126-005-6029-6https://www.pnas.org/doi/10.1073/pnas.0810311106https://www.pbs.org/newshour/science/how-a-snails-shell-gets-its-twist[Butt One More Thing]Wood-boring bivalve that creates fecal chimneyshttps://link.springer.com/article/10.1007/s12526-022-01306-zhttps://www.fieldmuseum.org/blog/down-and-dirty-most-unusual-bivalve

Welcome to SciShow Tangents, the lightly competitive science knowledge showcase. I'm your host, Hank Green. And joining me this week, as always, is our science expert, Sari Reilly. Hello. And our resident everyman, schultz hello i have a piece of uh update you may have heard in our in our credits we talk about faith schmidt faith is going by eve now my grandfather did this too and actually my parents said this to me as i was going to college they were like your grandfather changed his name he like stopped going by his middle name and went by his first name when he went off to

to college so you can totally be bill or will or willie or william or whatever you want when you go off to college like and i was like no i love my name and that's weird that you would think that i would i would want to do that but it's always an option sam who, who would you become? Well, I don't like my name very much. I've gone on record as saying this. I've never been able to think of a better one, but one time I asked David Sedaris. You want me to call you Schultzy? No.

One time I asked David Sedaris what I should change my name to, and David Sedaris said I should be S. Douglas Schultz. I think that's pretty good, right? S. Douglas. Is Douglas your middle name? Douglas is my middle name. I could be Doug, but I don't feel like a Doug. I don't think I'm a Doug. I'm looking at you and I don't see a Doug. Maybe when you're like 70, you could be a Doug.

A Doug, old Dougie. What do you think my name should be? I don't know. Dougie might be all right. Dougie. I'm not a Doug, but I am a Dougie. You're more of a dougie that's a fun name my wife has a theory that all men are either a dan a danny or a daniel everybody's one of those i think i'd be a i think i don't know i'm a danny trending dan i think i wouldn't be a daniel yeah i think so your sun sign is is Danny. Your rising is Dan. I'm a rising Dan.

I'm worried that I might have ended up a Daniel. No, you're a Dan. Okay. Okay. Thank you. Dan Green. I think Daniel is the one who started 20 businesses. Yeah. But you're Dan too. Dan is the one who runs them.

Yeah. And then Danny is like the one who humped that fish. And then Danny is like the one who humped that fish. We all, all of us contain three wolves. Dan, Daniel, and Danny. Sarah, what do you think? Sarah, you have such a great name, but I don't know. Where are you at?

Yeah, well, I hated my name because no teacher could pronounce it. Because the full name is? Ceridwen. Is that what they didn't like? Either. Either they couldn't do it. A lot of it was Carrie. A lot of it was Cerie.

Now that the iPhone came out, Siri was a big one. But also there were just so many weird permutations. I got like, my full name was Gerwin once. I got Gary because people just misread the C as a G because for some reason that was more legible. Gerwin? Is that what somebody called you? That's great. Someone called me Gerwin and I hated it. I think you should be Gerwin. It was during a school assembly when I won some sort of like sixth grade award for being a good student. And then they called up Gerwin Riley. And I was like, that simply can't be me.

That's simply not me. That simply can't be. And then my teacher was like, I think it's you. And I was like, Mr. Frank, it cannot be me. And then I cried a little going up. Don't call me Gerwin from now on. Please don't. But so I seriously thought about changing the pronunciation to Carrie when I went to college. I was like, now's a fresh start.

Similar thing. I wasn't prompted by anyone. But I was like, I could just switch it to Carrie and it would be so much easier for everyone. I think I could have pulled off Will. I think I could have lived as a Will. Yeah. I think so, too. Yeah.

So we've got S. Douglas, carrie and will here for your episode of what a weird alternate reality we've created i'd prefer to go under a pseudonym uh if you're watching the video podcast this is not sary riley this is some other person this is a slime monster here yeah carrie just ran a full mile in dress clothes to get here slightly after time because the trains broke. Aw, you could have pretended like she was on time instead of saying she was slightly after time. She didn't even make it. I just made it by running. No, I was late. Well, it's not easy to make mass transit work is what I've heard. I'm glad it's not my job.

Every week here on SciShow Tangents, we get together to try to one-up a maze and delight each other with science facts while also trying to stay on topic. Our panelists are playing for Glory and for Hank Bucks, which I will be awarding as we play. And at the end of the episode, one of you two will be crowned the winner. Now, as always, we're going to introduce this week's topic with a traditional science poem

this week from Sam. Got a baby chicken that needs securing? I think a shell would work quite well. A mollusk in need of a home that's enduring? I think a shell would work quite well. A turtle that wants to not get ate? I think a shell would work quite well. A nautilus that doesn't want to be shark bait?

I think a shell would work quite well. A chocolate candy you don't want melting? I think a shell would work quite well. A candy you don't want melting i think a shell would work quite well a shrimp that needs to take a pelting i think a shell would work quite well so if you've got the chitin to spare and you need some protectant for your derriere by now i think you should be able to tell that a shell would work quite well. That's cute! I love that one. The topic for the day is shells,

which Sam has gone ahead and explored the reality that there's a wide variety. I had not considered the candy shell, but now I am thinking about them, and I love them. No, I searched things with a shell. One of them was a coconut, one of them was an M&M. So, you know. So, Zeri, what's a shell? Is this a hard outside?

Yeah, I think that's it. It's a hard casing or covering in some sort. And they can be made out of all kinds of things. You can have chocolate shell, you can have one made of plant matter in the case of a coconut or like a seed, the husk or the hole is also sometimes called a shell. You shell a pistachio. There are plenty of calcium-based shells. So like mollusk shells are generally some form of calcium carbonate secreted to form those structures. Sam mentioned chitin, which is a lot of crustacean shells are made of that.

Shells can be keratin. In the case of like a, I think an armadillo. The fingernail stuff. Those are like hairs and shells. Yeah. Yeah, The fingernail stuff. Hairs and shells. Yeah. Yeah, the fingernail and hair stuff. Do my fingers have shells?

I think they do. I think they do. Little shells? Finger shells. Yeah. Because they're definitely much more like shells than nails.

Is your skull a shell of a type? Because it has a brain in it. You can't have an interior shell. Can't you though? Some octopuses have made their shells into their bones right but you don't call them shells anymore i think there's something exterior to a shell

because because a turtle shell is made of bone but it's more out than it is what if you had a skull out of the head that still had a brain in it, then would it be a shell? If your skull was like a little umbrella over your head, like a hat, if your skull was a hat. And it could go like that. I've seen some characters in science fiction with this. Yeah, a Frankenstein kind of situation. I don't know how he made his head so flat. I don't either. He was made out of other guys. Did he find a guy with a big flat head? Yeah.

He was a normal head for that. This would be the perfect flat head. Yeah. They could have packed extra flesh on too, kind of like built it up. Have you ever done pottery? You make mistakes all the time. You're just squishing on. Oh, yeah.

Frankenstein. Dr. Frankenstein just kept messing up and he was like, okay, I'll cover that. Yeah. Let me just add a little bit more there and I'll make it look, it's fine. That's probably what happened. The other shells that came up when I was looking this up in relation to science is electron shells, which are like the layers, the energy levels that are mostly just helpful tools for us to picture. Like the word electron shell is more of a...

More of a concept than like an actual thing that you could hide under to protect yourself with. If you were tiny, tiny, maybe. It's still a use of the word shell to mean a kind of casing. But in this case, a much more metaphorical or visual aid as opposed to an egg that you can pick up yeah it that's not a shell that's just an idea that we needed a word for and boy do i not want to talk about electron shells yeah i've done it enough i wanted to mention it so we didn't get called out but i also do not want to try and define an electron shell because I feel like I'll just get in trouble from the real chemists or the quantum physicists.

The science police will come after you. Yeah, they're not even chemists, those folks. And do we know anything about this word? The origins of the word shell are just as varied as the many uses of it nowadays, where we just needed a word for something. And we use the word shell or the root word of it, which is the Proto-Indo-European skel, S-K-E-L, which does not inform skeleton, but is more like scale or shale or shell. And so we used it for anything that kind of had a scale or a rind or a bark or an outside thing, both in the like a hard outer covering that you saw in nature as you were cooking. covering that you saw in nature as you were cooking. And then when you were specifying like shells on the beach, all of those, you used a very specific word. So you'd say there's a cockle shell or a muscle shell or an oyster shell or a scallop shell in the same way that we still

call out those specific organisms when we're talking about their specific shells. But I think nowadays there's a connotation of when people think of shell maybe one of the first thing they think of is like seashell in general but back then it was very much like it's an outside thing you could call any outside thing that you needed to remove or deal with a shell i've looked this up and skull is actually related to shell so maybe the skull is a shell at least etymologically so boom well done sam once again what a champion well here's the thing check this out if you have a candy shell but it's cold and then you do a chocolate shell on top of it that's now a chocolate candy shell. That's like what the skull is.

But instead of you've got like the the candy shell is the skull and then the chocolate on top is the skin. Right. Not an effective shell. It's like kind of a

goopy outer layer. Yeah. So it's more like a candy shell with hot fudge on top because it's not two shells. Yeah. It's a candy shell with hot fudge on it.

And if I was a giant and I ate people's heads, I'd probably think of it as having a shell. What a little treat. A little crunch to it. It would crunch. Maybe that's the new definition of shell. If it crunches, it's a shell. That was already the definition of crust.

So that can't be the definition of shell too. This is why we're not in charge of defining words i'm so happy for it and since now i think i mostly know what a shell is it's time to move on to the quiz portion of our show this week we're going to be playing shells truth or fail there are many peculiar things going on in our universe that involve shells but only some of the things that we think about with shells can actually be achieved. So today we're going to be playing truth or fail shell edition. There's three stories featuring shells. Only one of them is true. It's up to you to figure out

which one is true. It could be story number one. Scientists developed an app called snail snap that allows people to upload pictures of snails so that researchers could learn more about how the color of snail shells is changing depending on their location. So it's like Snapchat, but it's just snails. Snailsnap. found a rare type of exoplanet that they call conch planets because their winds run in a distinct cycle that stirs rocks on the surface into a spiral pattern similar to the spire on conch shells. Or it could be fact number three. Archaeologists were using a CT scan to study the wrappings of an Egyptian mummy when they found a layer containing an elaborate design made with shells of large foraminifera, a type of amoeboid protist. So is it Snail Snap, story number one,

an app that lets users help snails take their shelfies? Or story number two, a rare exoplanet that's been found to have distinctive spirals similar to a conch shell? Or story number three, Egyptian mummies wore amoeba shell jewelry. Wouldn't an amoeba shell be like infinitesimally small? Yeah, they're super small. They like collect all together into big piles. So you can, I had a roommate in college who studied 4M fossils.

But you could be out in the world and see one. You would usually see a bunch all okay okay i feel like pictures i've seen they're like a sand on a beach almost you just find like a pile of them hmm that doesn't sound jewelryable to me but i guess you could roll the mummy in it you know get them nice and coated up i think that the idea is that uh it's like uh imagine like glitter paint situation oh you like put the paint on and then you put the and then like then blow it off right okay okay yeah exactly like that i love the idea of snail snap yeah i want to be on there instead of other social media i'll trade it all i'll trade all my 5 000 twitter followers for snail pictures do you need a special app for the snails though

couldn't you just tell your friends to send you pictures of snails there are a lot of these apps already that that sort of do citizen science stuff okay they're like plug into an existing thing i haven't made any progress so far. You're shooting down all my ideas. Well, what do you think about exoplanets? I think that's wrong. Cause I think that when I was searching for a fact for this episode, I saw another kind of exoplanet named after another kind of shell that this

one is a, is a embellishment of. That's very metagamey of you. Well, it's not, I've saw it. It's not metagame-y of you. Well, I saw it. It's not metagame-y. It's just lived experience. I guess. This is your science self. You now know a thing,

and that's a different shell planet exists. Yeah. I think I'm going to go with the shelfies, the snail snap app, because I don't know where foraminifera fossils are. I feel like I've seen them by the ocean. I haven't personally seen them. I've seen pictures of them or read about them by the ocean. So I think the snail

snap app is the most likely of these three. Is Egypt not by the ocean in some places? Got a lot of ocean. That's very embarrassing for me. No, no. I'm going to go with the 4M and Nifero

one because I think that just is like evoking an image in my head of a bedazzled mummy. And I'm going to go with the Snail Snap app because I want it to exist. I want researchers to be like, hey, let's take colorful pictures of snails and understand where they're from. I'm leaving

in that you don't know where the ocean is i'm sorry i ran here i am really bad at geography i am sarah palin levels of bad at well researchers in the netherlands wanted to see if they could develop a citizen science method to study evolutionary change in urban centers. And thus, SnailSnap was born. Damn. It's real. SnailSnap is real. It's linked to an existing Dutch citizen science platform called something in Dutch.

Users have to upload pictures that they found, but they didn't need to add any data. The app was downloaded over a thousand times and received almost 10,000 images of the particular snail they were trying to study. After removing certain pictures that couldn't be categorized, they had like maybe almost 8,000. And they could sort that by habitat type and shell color. And they found that shells in urban environments were more likely to be yellow. Snails in non-urban were more likely to be pink. And that supports the results of experimental work that's shown that yellow snail, yellow shell snails seem to survive better in hotter temperatures.

And pink have a higher body temperature compared to the yellow snails. One possible explanation is the yellow shells are able to just reflect back more solar radiation, and that keeps them cooler like wearing a white shirt on a hot day. Good job, guys. Everybody worked together to find out things about shells. And Sam, you were absolutely

right about eggshell planets. So there is a rare type of planet called an eggshell planet that has a thin crust that's super brittle, no mountains, no plate tectonics. And scientists described a method to use a planet's size and age and distance from its star to identify whether it is an eggshell planet as those factors impact the thickness of the planet's lithosphere. There is also apparently a list of almost 3000,000 nearby exoplanets fitting certain parameters that was published in 2014. And the list is called Conch Shell, which stands for Catalog of Nearby Cool Host Stars

for Habitable Exoplanets in Life. Great. That's a good one. And I promise you, you will not be able to find all of the necessary letters, but they have found them somewhere. I know astronomers sometimes do a little stretch. That one is a doozy. It's a big stretch.

I would say. There's a lot of extra letters. They got kind of part of the way there. They're like, well, this is too fun not to do. So that leaves Sari with one point and Sam with nothing. Next, we're going to take a short break. Then we'll be back with the Fact Off. All right, everybody, get ready for the Fact Off.

Our panelists have all brought science facts to present in an attempt to blow my mind. And after they've presented their facts, I will judge them and award them with Hank Bucks any way I see fit. But to decide who goes first, I have a trivia question for you. So the nautilus, you've heard of it. It's a cephalopod with an external shell. And you may have seen it used over and over again as an example of the golden ratio at work. And according to this idea, the nautilus shell forms that golden ratio spiral means that with each quarter turn, the spiral gets wider by a factor of five, which is approximately 1.618. But does it? does it in 2005 a mathematician was like i don't think it does and got some shells at the california academy of sciences and found that the ratio was 1.33 and then a feud began and an art professor

was like you didn't look at very many shells i'm gonna look at more shells than you and he worked with the the smithsonian national museum of natural history to get a bunch of different shells how many shells did this guy in his uh in his feud it's not a feud i'm sure they got along fine but anyway how many shells did he measure wow the gold that being the golden ratio is the only thing i know about anything i know it's very it's not true the golden ratio i don't know we're about to find out he's's going to measure more shells. And at the end of the, when you guess, we're going to find out. It's going to be great. Okay.

Okay. Okay. He measured, gosh, professors are probably so stubborn. He probably measured 800 shells. He probably measured a thousand shells. I changed it to a thousand. I think, I think he measured like 700 shells. Yeah, you don't think he measured a thousand shells.

Not quite a thousand. Sari's our winner because it was only 80, which was still a lot more than the other guy measured. What a quitter. I know. He might still be wearing Big Talk to be like 80. All of that, and he measured 80. And at the end of that, he measured 80 and at the end of at the end of that he measured 80 and his was even smaller the average ratio was 1.31 no the golden ratio as a i guess it's not a lie but

yeah the golden ratio continues to be real but uh this is not an example of it none of the species that he looked at matched the golden ratio uh the ratio spirals of the crusty nautilus were about 1.365 which is a roughly four to three ratio which is a close approximation of the meta golden ratio bartlett's words quote it is a pleasing mathematical number with notable generative geometric properties just as the golden ratio so he's like this one's also good this is very close this is one of the saddest things i've learned on sci-show tangents i hate this it's wild it's the nautilus is the thing you see yes it's the only thing you see basically well i think like there's like that cauliflower that like fancy cauliflower got that golden ratio

going on that's true i bet that doesn't either i bet some scientist is like no no one even checked yeah i love that no one checked like finally someone was just like but i don't know that like i looked at a picture and it doesn't really line up all right sarah that means you get to go first today i would like to introduce to you the crabattery a battery made with crab shells this name is me editorializing because i want to fail because it's not this one uh this is me editorializing because i want to have fun i'm not a coward uh like these scientists but the battery in question is more broadly made with chitosan, which is a more water-soluble derivative of chitin, which is a structural polysaccharide in crustacean shells, but also fungi and insects. And the basic structure of any battery is that there is a positively charged terminal called the cathode, a negatively charged terminal called the anode, and then some stuff in between to help electrons move around. terminal called the anode and then some stuff in between to help electrons move around the stuff which is called an electrolyte can be a liquid a paste or a gel or a crab or a crab uh well a

derivative of a crab shell uh in a lithium ion battery there's a liquid electrolyte that helps lithium ions move between the two ends but in a crabattery uh there is a firm gel electrolyte that helps lithium ions move between the two ends. But in a crabattery, there is a firm gel electrolyte made with chitosan that helps zinc ions move between the two ends. My understanding is that zinc ions have been trickier to work with in general in batteries because they tend to clump up in a liquid electrolyte and form little growths called dendrites that can short circuit the battery if they get big enough. But this chitosan gel actually stabilizes the zinc enough to prevent this problem. And according to a 2022 study from the researchers that created it, the Crabattery is 99.7% energy efficient after 1000 battery cycles.

And I think that's on par with many battery goals. Hank is nodding and he's done more eco type research than me. He's the eco geek himself. Yeah. The hashtag eco geek. But just to give everyone else some context, from what I could find, batteries kind of run the gamut of trying to stay more than 80% efficient for anywhere from 500 to like in the extreme cases, 9,000 cycles, depending on what I read. And on top of that, this crab shell-infused electrolyte gel is also biodegradable. When the team took the gel, buried it in soil, microbes broke it down over the course of around five months

because they can break down chitosan, and zinc is relatively non-toxic, which isn't the case for many batteries out there that need to be specially disposed because they contain amounts of toxic metals. And of course, with research like this, it's hard to tell exactly what's going to be mass produced out of it, but the fact that it exists and researchers are experimenting with turning crab shells into all kinds of batteries i found another group after this that are working on making crab carbon anodes uh for a different kind of battery these crabs better watch their asses we're after all yeah right we're happy i am like i'm looking at these pictures and it's also kind of making me a little hungry yeah crab gel sounds delicious you guys too

much to offer us yeah you got the meat you got the electrical engineering you got everything but yeah it's a fun way to talk about electrical engineering and use the waste products when you eat those big old crab legs instead of tossing them turn them into batteries put it in the gas tank of your car and you can drive yeah i love the idea that people who run crab restaurants are just gonna have this like tremendous new income stream they'll be the richest people in society suddenly it's like why is this place so cheap and it's like no it's just we're really just a uh just a house for crab shells yeah crab crab battery do they call it a crab battery

no that was made that up because she's a genius i just wanted to add something they call it a Crabattery? No, that was all me. She made that up because she's a genius. I just wanted to add something. They call it a... Gerwin Riley. They call it a sustainable chitosan zinc electrolyte for high-rate zinc metal batteries. I just feel like... Some days I feel like the world that we inhabit is just so technologically advanced. And some days I feel like it is just so far behind. Does the crab battery make you feel advanced

or like we're making batteries out of crabs? It makes me feel like in the future, batteries are going to be really amazing. And actually right now, all these amazing batteries that we think we have are terrible. All right, Sam, what do you got for us? Hey, I don't think we can do an episode

about shells without talking about one of the unofficial mascots of SciShow Tangents, hermit crabs. Hermit crabs, as we all know, are cute, weird little crustaceans that have evolved to squeeze their weird butts into discarded mollusk shells. And accordingly, their whole lives revolve around these shells, finding new ones when they get too big, trading shells with other hermit crabs, fighting other crabs for the shells. new ones when they get too big, trading shells with other hermit crabs, fighting other crabs for the shells. And fittingly, a lot of their brain space is devoted to being able to tell when one shell is better than another. They touch the shells, they weigh the shells, they check them for damage, and then they compare those new shells to the shells that they're currently living in so they can make the decision about which one's better so that they can live their best little hermit crab lives. So, you know, it'd be really sad and sucky if there was something that hindered

their ability to select the best shell, especially if it were something ultimately caused by humans being humans. Well, in a 2020 study, a team of researchers studying the effects of microplastics on ocean life exposed a tank of hermit crabs collected from a beach in Ireland to microplastics for five days. They then removed the hermit crabs from their shells and put them in new shells that were 50% too small for them. After a couple hours of acclimating to their new bad shells, they were placed in a tank mere centimeters away from a new perfectly sized shell. And compared to a control tank of crabs not exposed to microplastics, the plastic exposed crabs were less likely to investigate the

perfect shell. And then when they did check it out, they were less likely to trade it in for their crummy too small shell, even after investigating it for like as long as the control crabs were investigating the perfect shells that they ended up moving into. And a related study pitted hermit crabs against each other to fight over shells and found that plastic exposed hermit crabs were slower and had less energy than non-plastic exposed crabs. So the researchers concluded that something about the microplastic exposure was hindering their ability to assess the shells, but it's not really clear totally how. So it could be something like damage to the brain, but other studies on crustaceans and microplastics have shown that they induce feelings of false satiation in crustaceans so that they don't eat as much and they don't have as much energy to spend on searching out a new shell, maybe is one of the thoughts.

And the hermit crabs weren't seen eating the plastic either. So it's just like being near microplastic is messing up. Poor little hermit crabs. So in conclusion, mankind has gone too far this time we can't hurt those guys this isn't good because i spend so much time around but all kinds like macro and microplastic i yeah everywhere yeah and if it's if it's making it so that crabs can't make good decisions i definitely am not making good decisions oh that's a good point i didn't even think about that.

But yes, probably. Maybe they can make fine decisions. They just feel fine. It's just like an anti-anxiety for them. That's what I thought at minute first. But it's good enough. Yeah. Feelings of satiation.

It's like, eh, whatever. I'm doing all right. I'm giving them a little ennui. They're probably feeling ennui just from my personal experience because that's like the main emotion yeah so it's either going to be the crabattery or the microplastics making poor innocent hermit crabs worse at picking out shells i am i don't know i don't want to be sad and also i was a little bit more astounded by the crabattery so i think i'm going crabattery that's fine we all love the crabattery don't I think I'm going crabattery. That's fine. We all love the crabattery, don't we? But I do also love hermit crabs. I also love to be reminded that our unofficial mascot after all of these years remains hermit crabs.

Yeah. I kind of forgotten about them myself. And that means that Sari is the winner of our episode with some amount of Hank bucks. And also it means that it's time to i ran for those hank bucks worth it and now it's time to ask the science couch where we've got a listener question for our couch of finally honed scientific minds at azarine tweets asks why do so many shells spiral rather than being built straight? Our hair and fingernails are straight, I guess.

I could usually say something, but I can say nothing. All I can say is that there are two pieces to it. There's how it gets done, and there's why it gets done. And I don't know either. And I can do half. You can do half you can do half maybe it's like there's a advantage to having like the internal like the internal structure of a spiral thing makes it really strong sari can only do half which half i can do the how not the why no idea we don't know

sam offers a guess at why and then sari's got a how for us yes well because the why it's like they're all so especially when you get into the intricate ones like the venus combs and the conch shells and things like that that have all these protrusions on them in addition to the spiral like they look like art but also why did they adapt to make those shapes so particular? So the way that these shells get made is they're secreted over time, which I think is a weird thing to think about. Because if you're like a shell is a house, shouldn't it just exist? It doesn't just exist. And it gets secreted over time and grows with the organism. And that's how, in general, the spiral gets made.

the organism. And that's how in general the spiral gets made. So the shell material is secreted by a kind of tissue on mollusks called the mantle, which is in contact with the shell and located just like under the lip of it. And the two things that it mainly secretes are proteins, which add the structure of the shell, kind of like a steel rebar that you lay down in a building foundation. And then it excretes minerals, usually some form of calcium carbonate that creates everything else in the shell, like pouring concrete in. That creates most of the structure. The way that these shells are secreted, as far as we can tell, the Y is a question mark, but it is some sort of neural network, genetic switches. For example, in one species of snail, scientists have isolated a

single gene that if you turn it on or off, it changes the direction of the spiral on a snail. So there are very, very precise mechanisms in place that cause the secretion to progress in a certain way that makes a very precise spiral pattern. But the three factors that affect the way that a shell takes place is the way that the shell expands over time. So they start by secreting just a tiny, tiny bit and gradually secrete more and more and more to make the mouth of the shell wider and wider to fit their current body size. And as the organism grows, it expands the size of the shell. The second bit of it is rotation. So by depositing slightly more mineral and proteins on one side than the other, that's what makes the shell grow and start to

spiral in a direction. And then the third rule also sounds like rotation rotation but it's a it's like a twist so you can in addition to depositing more material on one side than the other you can change at what points you deposit material and i think that twist movement is also what causes those spikes where you could just have like an extreme deposit all at once and then stop and then twist and then extreme deposit at different points in the mantle. And all like those three factors of secreted mostly calcium carbonate and a little tiny bit of protein in mathematical models can make all kinds of different spiral shaped shells. I don't animate, so I don't know if this is going to be a bad metaphor. Maybe, Sam, you can step in. But it's like an animate, I don't know, you like squash and stretch in

different directions and you can make all kinds of different shapes. Or if you're like squeezing Play-Doh through a tube, if you just like manipulate little bits of the way that it's coming out, then the shape itself will completely change. Right. It seems like it would be too much work to have a shell. I'm happy to be squishy all over. You got to evolutionarily invest in it. They put a lot of points into, I got to be protected. Then they're just sometimes a little blob otherwise.

They min-maxed themselves into blobbiness. I kind of have a hard time, and I apologize to the mollusks for this. If they're always inside of a shell i don't really think of you as an animal what do you think of them as i mean i think i mean i know like they are animals but like that's not what my mind they're just like goop like a animatronic rock at that point just a little decoration thanks sam for saving me yeah sari at that point they're just like an animatronic rock oh that's hilarious but if they've got a bunch of tentacles and eyes and stuff then i'm like that's a

yeah yeah barnacles i feel the same way i'm like that's not a thing no way you just don't like the goops of the animal. Yeah, I want to see some more differentiation of shapes. Hank makes a hard stance on cellular differentiation. Not good enough. Not enough cell types. Not a cool creature. Look, if you want me to think that you're an animal,

I want your shell to open up and for a little face to pop out. Oh, okay. It's like, hey, here's my eyes and my mouth smiling at you. That works for me. Yeah. Even if the mouth is like terrible and tucked in amongst all the tentacles. I'm still like, that counts. You want the clam to come up to you and go, hello, Hank.

Yeah. And then it can be an animal. I need Jim Henson to get involved and then I can count you as a real live animal. Yeah. If you want to ask the Science Couch your question, you can follow us on Twitter at SciShow Tangents, where we'll tweet out topics for upcoming episodes every week. Or you can join the SciShow Tangents Patreon and ask us on our Discord. Thank you to at BearStravaganza on Twitter, Chris on Discord, and everybody else who asked us your questions for this episode.

If you like this show and you want to help us out, it's really easy to do that. You can go to patreon.com slash SciShowTangents to become a patron and get access to things like our newsletter and our bonus episodes and also special thanks to our patron, Les Aker. And don't forget, once we hit 700 patrons, we're going to do that Minions movie commentary. Sam, where are

we? As of June 13th, 2023, 647 patrons. I think that's the same exact place we were last time. Guys, tell your parents. If each of you tells your parents, we could easily triple this

number, I think. Yeah, you know, parents don't love anything more than Minions. And you just can, like, mumble the piss part. You say, oh, man, Mom, you love a Minion, right? My favorite podcast, SciShow Tangents, is going to talk about Minions next. So please support them. Yeah, and your mom has a Minions t-shirt on. This episode is released, and then she says, oh my, but at least she gave us her money for a little while first.

That's right. So go to subscribe. We are tantalizingly close to discovering exactly how much piss a Minion can really hold. Second, you can leave us a review wherever you listen. That's helpful. It helps us know what you like about the show. It also helps other people know what you like about the show. And finally, if you want to show your love for

SciShow Tangents, just tell people about us. Thank you for joining us. I've been Hank Green. I've been Sari Reilly. And I've been Sam Schultz. SciShow Tangents is created by all of us and produced by Sam Schultz. Our associate producer is Eve Schmidt. Our editor is Seth Glixman. Our story editor is

Alex Billow. Our social media organizer is Julia Buzz-Bazio. Our editorial assistant is Deboki Chakravarti. Our sound design is by Joseph Tuna-Medish. Our executive producers are Nicole Sweeney and me, Hank Green. And of course, we couldn't make any of this without our patrons on Patreon. Thank you. And remember, the mind is not a vessel to be filled, but a fire to be lit. But one more thing. Clams and other bivalves have two fleshy tubes called siphons one for inhaling water and one for exhaling water and typically they also expel poop out the exhalant siphon to get it away from their bodies but one wood-eating bivalve called xylophaga dorsalis has such a short exhalant

siphon that its poop piles up to form a fecal chimney in and around their shells which is exactly as gross and confusing as it sounds uh this woody poop tunnel restricts the flow of water which feels like a huge liability in a 2022 paper though researchers suggested that because these bivalves cluster in dense groups and can tolerate low oxygen levels their fecal chimneys might help them out compete other wood eating organisms we still don't know exactly but there has to be a reason they're piled in poop yeah it does there yeah i don't know just an accident they just evolved so poorly well you know if it's not doing any harm, it sticks around. But I am glad to know about fecal chimneys, just because it's a fantastic couple of words to end up together.

Do they get presents from Santa?