Secretly Incredibly Fascinating - Crabs

Episode Date: February 19, 2024

Alex Schmidt and Katie Goldin explore why crabs are secretly incredibly fascinating.Visit http://sifpod.fun/ for research sources and for this week's bonus episode.Come hang out with us on the new SIF Discord: https://discord.gg/wbR96nsGg5

Crabs. Known for being crustaceans. Famous for being crabby. Nobody thinks much about them, so let's have some fun. Let's find out why crabs are secretly incredibly fascinating. Hey there, folks. Welcome to a whole new podcast episode, a podcast all about why being alive is more interesting than people think it is. My name is Alex Schmidt, and I'm not alone because I'm joined by my co-host, Katie Golden. Katie, what is your relationship to crabs, crabs, crabs, crabs, crabs, crabs, crabs, crabs. Begin the chanting of the crabs. Yes. Good. Crabs. My quick one is that this made me realize I'm a tiny bit grossed out by these animals. It's not phobic, but I don't love them either. And I do eat their meat. You struggle with sea life.

Yeah, that's just me. You struggle a little bit with sea life, yeah. The ocean is my opponent. So I am into Mr. Crabs now. That's probably the biggest positive thing from SpongeBob. But, you know, that's about it. Our favorite crab who does wage theft. So, yeah, no, I like crabs. I don't have a problem with them. They

do not gross me out. I had a hermit crab as a pet when I was a kid. I don't recommend them as pets. I don't think they make very good pets. This one crawled into my armpit, started clinging on to the skin of my armpit and would not let go. And it was enormously painful. And I couldn't pull it off because I was worried if I did that, I would like rip its little arm off. So I just had a crab in my armpit for like a couple hours. Shoot. Couldn't do anything about it.

I was 12. Wasn't sure what I was supposed to do in that situation. Did anyone around you intervene? Were your parents like, do this? No, I just was too embarrassed to kind of like draw attention to it. And it let go eventually. No harm, no foul. Just uncomfortable.

It was very uncomfortable having a crab in my armpit. Did the crab have a name? Did it? I think it was just called crab it because it's the kind of extraordinary pet where you don't necessarily have to name it like it's the only hermit crab in the neighborhood or whatever so it's crab yeah it's just my crab yeah no it's the only crab we had uh in the family so yeah not not so difficult to uh call it out yeah but uh i don't know i i like crabs i appreciate crabs i like the whole concept

of crab shape uh repeatedly evolving in nature among different arthropods, which is fun. There's a lot of cool stories about crabs. I'm just excited. I'm here for it. Yeah. And a whole bunch of people suggested this on the Discord. There was a real movement in the polls for crabs, and it has been really fun to research. I am more into them now and was not quite anti them. I just noticed an anti-crab in myself when I got going, and it's mostly resolved. You got to work on that. Do better. Crabs.

On every episode, our first fascinating thing about the topic is a quick set of fascinating numbers and statistics. This week, that's in a segment called... There ain't nothing short of figures. And some facts to round them out when it comes to learning something. Stats and numbers coming down. Nice. That was a good one. Thank you. That was from Doc underscore Lobster on the Discord.

So a fellow crustacean. Yeah. Please submit a new name for this segment every week. They're silly and wacky and bad. Submit through Discord or to SifPod at gmail.com. The first number this week is nearly 7,000. Crabs. It's just fun to say that word, huh?

Crabs, crabs, crabs, crabs, crabs. I'm going to go around town like, and a crabs to you? And a crabs to you? I'm going to guess that there's nearly 7,000 species of true crabs. Yeah, that's the number. That's that one estimate. And it's a pretty rough estimate because it turns out the world is just full of all kinds of new crab species that we discover all the time. Lots of new crabs. I mean, some things like it's also crustaceans that are kind of like re-evolving into crab shapes or parallel evolution of multiple crab shaped crustaceans. Some of them are actually not like true crabs because they started out as a type of crustacean that's actually maybe more closely related to lobsters or crayfish or

something. But then they may get turned into crab because apparently the crab shape is just very good, a very good shape. And you see that in other species as well, like other arthropods, even spiders, just like crab shape is very good. And so I'm not surprised that there are so many species of crabs. Yeah. And that leads us into, I think something a lot of people are excited about, and then there's more to it, which is a quick takeaway. Number one, many arthropod species separately evolved to match a crab's shape and then many crab species separately evolved to walk on land yeah the scuttle is such a powerful weapon in the evolutionary arsenal that everyone's doing it

everyone's scuttling yeah like worldwide it is very common among a lot of species. And then I think I heard a meme version of this initial thing about crab evolution that is a little bit more extreme than what it is, because the term is carcinization, and that means evolving or changing into the shape of a crab. The meme I had heard is that like all life is going that way. No. And it turns out it's mostly arthropods. It's mostly some things that are a little crabby already. It's fun to joke about that.

Like we're all turning into crabs, but it is arthropods. Yeah. I would welcome the opportunity to evolve into more of a crab-like shape. That would be fun to kind of zoidberg it up. But yes, arthropods are the ones. And arthropods are animals from crustaceans to scorpions, spiders, insects. Those are all arthropods. Yeah, I hadn't realized the family is so big.

It's big. Scuttly things. Creepy crawly stuff. Yeah, a lot of stuff the family is so big. It's big. Scuttly things. Creepy crawly stuff. Yeah, a lot of stuff with exoskeletons and a lot of other species are very closely related to crabs, like scorpions and spiders. And in particular, an animal we call the horseshoe crab is kind of considered almost more of an arachnid evolutionarily. But it looks crabby and it lives in water.

And it's like, in terms of like the crab shape, there's both convergent and parallel evolution. Convergent evolution is when you have two ancestors who did not have the same trait, and then you each like independently evolved it. And now you both have the trait. So you're converging on this trait, whereas parallel evolution is where your ancestors shared that trait, but you're both in parallel with each other retaining this shape. So like it's a lot of conversion evolution with like the crab shape where it's like maybe their ancestors didn't really have they didn't both have the same like crab shape, but then they ended up like coinciding upon the crab shape. Yeah. Both of those processes are so amazing because it's, I know it's over millions of years and it takes a very, very, very long time beyond any of our lifetimes, but it also just feels fast when you read about it in a book. Yeah. It's like, oh wow, they just all did it

together. They all met up at the train station just, oh, wow, they just all did it together. They all met up at the train station just in time, you know? They all sort of like decided it's Wednesday, it's be a crab day. Wednesday is where crabs stay. No, yeah, it is a typically very long process evolution. And so it's interesting to see certain patterns where you have similar shapes or sort of like some kind of thing that keeps happening, like basically crab shape. But when we say crab shape, right, we're talking kind of like having bilateral symmetry of, you know, these

two sides, and then it's sort of in an oval kind of shape and side-to-side movement, a set of arms in front with like pincers. Like that is essentially the crab shape, right? Yeah. And there's numbers within this takeaway too. It turns out another key crab number is 10, and not everything has gone this way, but crabs tend to have exactly 10 legs in five pairs, which I never noticed or thought about. But they tend to have a front two legs with pincers on it and then the other eight legs for walking or standing. Those legs also tend to shuffle side to side because the leg joints are just a simple hinge pointing sideways. Right. So kind of like we move the fastest going forward because our knees point forward, their

knees point to the side, so they move to the side. Imagine if we could rotate our legs such that we could point our knees to the side and then just start walking sideways. That'd be neat. I feel like I've seen dance crews do that specifically, but otherwise the rest of us aren't out here doing that. I would break several things if I tried that, but yeah, no, it's, it's, so that is the general thing where the, the eight legs are used for walking and two legs are used for pinching.

But like, there are some crabs that also use some of their walking legs for other things. I mean, like aquatic crabs, a lot of them, like they, they swim, they can swim, you know, decently. There's some crabs that have adapted their legs for actually certain decorator crabs that they have a pair of legs, not for walking or swimming, but just holding stuff on their bodies, like a little hat made out of algae or sponge and holding it onto them. So yeah, there's a lot of cool things that crabs use their legs for. And they're delicious. Right. It's such a central part of a crab to many humans. They're like, oh, it's crab fasting. I go get those crab legs. And then it's also almost kind of the most distinctive trait of them. Like some of the sources I was looking at called these animals decapods. Decapod means 10 legs. Deca is 10. And so it's a really important trait, even though I never counted it ever.

Yeah. Like I said, the scuttling is the defining characteristic of the crab because otherwise it's just a little oval, a little disc, but it's those little legs and the little pinchers, the little pincers, the pinchy claws that make it crab-like. Yeah. And like you said, these legs that they stand on can vary in purpose. And then the many species that we call hermit crabs tend to have a much shorter rear forelegs because those are strong short legs for holding the discarded shell onto the back of their body. And yeah, these vary, but also match up. And then with the evolution, the meme is mostly true, right? Like arthropods are doing this amazing thing where many of them converge or in a parallel way move toward a crab shape. They carcinize. A lot of this meme comes from one project by researchers at Harvard University and Florida International University who think that five separate groups of decapods all evolved toward crab shapes from different starting points, which is amazing and a whole thing.

Right. I mean, even like hermit crabs are not quote unquote true crabs. They're from a separate evolutionary lineage from like the quote unquote true crabs. And we call them hermit crabs because they're they look like little crabs, right? Like, I mean, they do have stuff attached to their butts, but still, like, they're so crab-like that it makes sense that we also call them crabs, but they come from a separate... They're all crustaceans, right? Like, they are in the same order, but still, it's very interesting

that something that is a very classic kind of crab, the hermit crab, is not, like, technically a quote-unquote true crab. Yeah, that was so surprising about the taxonomy. There's arthropods, and then under that is crustaceans. And then it turns out there are a bunch of different specific infra-orders of things that are true crabs or false crabs. And a bunch of stuff like king crabs are false crabs, even though they extremely look like crabs and are eaten and listed on menus as crabs. And like, there's a marine biologist somewhere who will be

like, these aren't crabs at crab fest. Too bad. Gatekeeping, crab gatekeeping. I do love, I do love the idea of false crabs where it's like, they're just wearing little fake mustaches. It's like, you're not a crab at all. You're a squat lobster. Right? Like it's a they're just wearing little fake mustaches. It's like, you're not a crab at all. You're a squat lobster. Right. Like it's a giraffe trying to hide in a tidal pool. Like, I'll just be a crab. Clap, clap, clap.

What crimes is that giraffe committed that it is trying to evade the law? Yeah. To evade the law. Yeah, and this key project that has helped the internet get excited about carcinization, some of the people on that team did a further new study that came out recently, November 2023, that I kind of find more interesting. But they did this study looking at fossil records and crab DNA to explore more crab evolution. And they think there are 17 different crab species who initially only lived in water and then surprisingly recently evolved to also walk on land. By recently, what do you mean? Like what time scale? Within the last 100 million years. Yes. There we go. So like yesterday, basically.

Yeah, essentially, evolutionarily, yeah. Like as we're taping, probably, getting out the water. It's like a little crab testing a little toe. They don't really have toes, but testing a little leg. Seeing like, eh, is it dry? Do I like dry? I don't know have toes, but testing a little leg. Is it dry? Do I like dry? I don't know if I like dry. Yeah, apparently the name for that thing that I think of as a cartoon fish walking on land,

the name for that is terrestrialization. Terrestrialization. Yeah, and apparently most species that have done that at all did that more than 300 million years ago. And so these crab species doing it within the last 100 million years, that suggests that maybe we can learn more about terrestrialization from them because it's an interesting and different timeline. Take a little microphone and say, like, why did you decide to come on land? Some crabs spend some time under the water and some time like on land, some are like almost completely on land now. There are some that like come on land, but then stay mostly like on the shoreline. And then like, they like to bury themselves in the sand. And it's

super cute, wet, sandy hut. So there's all sorts of I know it's so cute there and some that like will live on land but then like go back to the the ocean to reproduce like christmas island crabs do this kind of migration where they're on land and they live sort of in like uh moist forest floors most of the time but then they do this mass migration out to the sea to uh reproduce and then all these babies once they hatch do another mass migration back onto land. So it's very cool that there's all sorts of different types of land living for crabs. And yeah, and that's part of why the study is so interesting. It's exactly like you say, a lot of them still have some particular relationship to water.

them still have some particular relationship to water. And then apparently of those 17 species that terrestrialized, a few of them returned to living exclusively in water. This was a fad or a phase. And then they said, yeah, that was all right, but there's not that much food up here and I like it underwater and I'm out. I thought I'd like the dry. I didn't like the dry. It was too dry. They're not wrong. Pretty dry up here. That's how I feel. Using a lot of jergens. Did anyone tell the crabs about jergens? Then they might have stayed.

I mean, that's kind of, I mean, in a more, it's sort of a more short evolutionary time scale of like what happened with cetaceans, like whales. They are mammals, terrestrial mammals. And then they're like, it's too dry. Going back. We're going back.

And they did slowly evolve back into aquatic creatures. Although they are still mammals. They still got to be there. And all their adaptations, they still retained all these mammalian traits, but now they are, you know, fully swimming in the ocean, like dolphins, orcas, baleen whales. They all came from a common ancestor. Yeah, and it's so wild that studying that process in cetaceans could tell us about the process in crabs or the other way around and with all sorts of other species that were in or out of water at some point hundreds of millions of years ago. You just don't think of them relating at all, but that's one way. I imagine like sort of the personification of evolution, getting frustrated when animals can't

decide whether they want to go in or out of the water. Like, you just came out of the water. You want to come back in? It's like we're a bunch of cats. Crabs like to do both sometimes. Yeah. That brings us kind of back into more numbers because as much as there's carcinization toward crab shape in many species, then there's this astounding blossoming of all sorts of different crab species

and nearly 7,000 of them approximately in the world. And we just keep finding them all the time. One source this week is the book, Walking Sideways, The Remarkable World of Crabs. That's by Judith S. Weiss, Professor of Biology at Rutgers University, Newark. She says there was one project where a global network of researchers did expeditions across 10 years to try to create what they call the census of marine life. They finished in 2010 and they turned up 65 new species of just crabs within all their other discoveries and things. There was also a 2011 survey by a Smithsonian team. They looked at seven sections of dead coral in a few oceans. And in just those bits of coral, they found 168

new species of crabs. They're not even really trying to find that. It's just around. They get everywhere. There's this thing that has always fascinated me, which is there is this tiny species of crab that lives in the bromeliad, which is a type of flowering plant in Jamaica. They live on trees. And they're just sort of this, like, it's this leafy flowering plant. But then what happens is because it kind of forms this basin in the plant, it collects water. And so something like this tiny crab can actually live in the bromeliad. There are other species that sometimes live in these like, like frogs, but like, it is really incredible that like a crab can be like, yeah, I'll live in this wet flower in Jamaica. Why not?

I love that. Man, Ed, apparently that's not the only crab sort of doing that kind of thing. There's also a new species discovered 2017 in the forests of South India in the Western Gats Mountain Range. And it's a species that lives in the hollows of trees that fill with water and heavy rainfall. Oh, amazing. They just found pockets of water. I haven't even heard of that one. I'm a huge crab fan and I'm still learning about crabs

because there's too many crabs. There are. It's like, it's a bonkers amount of diversity. Even though I just think of the one red one at crab restaurants, there's so think of the one red one at crab restaurants. There's so many. No one red one. Mr. Mr. Crabs is the only crab I know.

No, but that's so it's so cute. They're just like, I'm going to live in a twee and justan version of frogs where it's just they love being places that are cute. Cute and like moist, like frogs. Cute and moist, yes. If it's moist here, I can crab it up. I can do it. Yes. So cute.

Yeah, that Indian one, it's got scientific name Kani Maranjandu and no common name yet. The first word is Kani because this was first observed by the Kani native people of that part of South India. And then like other university scientists came around later based on their observations. Always important to listen to local observations, especially when it comes to crabs. Yeah. So many of these little guys, and they're very diverse too. Even though they all kind of tend to have that basic crab shape defines them, they all have such different adaptations and different behaviors. Yeah. And the other maybe biggest variety is the size. Because even if they're all kind of a similar shape, the number here for the smallest crab is the pea crab species. Pea like a vegetable. P-E-A.

Pea. Pea crab. The whole body is about one third of an inch wide. Less than 0.85 centimeters. Yeah. And we'll have a picture of it just on somebody's like fingertip. It's pretty small. I know one of you wise out, smart Alex out there is going to say like, isn't the smallest species

of crab, you know, crabs like the... Oh, like the lice you get. Like the lice you get. From hooking up with people. Yeah. Yeah. The thing is, that's an interesting observation because those are not crabs, obviously, but they are arthropods, right? And as we mentioned earlier, arthropods do often evolve this kind of crab shape, even if they're not crabs of parasitic arthropod, the sexually transmitted crabs, but they are not really crabs. But they kind of look a little bit like tiny gross crabs. Right. That's such an interesting thing to clarify because it's not totally just a weird thing sex people are saying, you know? It's sort of like how scorpions and lobsters do look similar, right? Like, well, yeah, they're both arthropods.

They are related. Yeah, they're they evolve similar traits. They come from a similar ancestor and they evolve similar traits. Yeah, the world of arthropods, man. It's so varied. We did the small crab number. Here's the big crab number. The world's largest crab is the Japanese spider crab.

And just the carapace is more than one foot wide. The full leg span is up to 12 feet. Wow. So more than three and a half meters. It can give you a hug like twice, wrap its arms around you like all the way twice, which I don't love. I tolerate crabs very well. I like them. But when it's like when its legs are like twice as tall as I am, that's upsetting.

I don't know. Yeah, I don't need it in my house or whatever. Yeah, that's cool. But, you know, is there a prize for the most swole crab, which I think is like the coconut crab, just the chunkiest, toughest, beefiest crab? It's not technically the biggest, but I think that giant, the giant Japanese crab is like kind of spindly, but like the coconut crab is just like muscular. Exactly correct. Yeah. Beefiest crab. Exactly correct.

Yeah. Beefiest crab. Yeah. The next number is that the coconut crab, which is a species of land crab, it's large and strong enough to lift 60 pounds of weight. And it doesn't always eat coconuts, but that's the name origin is it'll like bust open a coconut with its might. Yeah. It's got a lot of PSIs with its claw strength. Yeah. More than 27 kilograms it can lift, 60 pounds.

That's incredible. Yeah. It's a crab. A big, scary, beefy crab. And also speaking of food, I had wondered what a soft shell crab is, because I've heard of that from Food. I'm linking Food and Wine magazine about it. They say that that's just kind of a different stage of a regular crab's life because arthropods have an exoskeleton both for protection and to kind of hold their bodies together. And they will molt that usually each year. It depends on the species. And so a softshell crab is just a crab that we captured before it regrew its exoskeleton so we could eat it in that particular state of being. When it's like, no, I'm naked.

No, I'm naked. It's kind of rude. And we're like, exactly. And, you know, yeah, it is pretty rude. That's rude and kind of perverted for us to bust in on a crab as it's changing outfits. And it's like covering its little crab body with its claws and going like, don't look at me. I'm naked. And they can't find a robe for themselves.

You can't get a robe if you're a crab. They don't make that. Another amazing number about eating crabs is 90,000 years ago. 9-0, 90,000 years ago. That's how long ago we think there's evidence of Neanderthals eating crabs. That's how long ago we think there's evidence of Neanderthals eating crabs. What's the evidence? Like an old sort of like bib, a prehistoric bib with a crab on it? Just crab fests carved into some kind of stone in Flintstones font.

Yeah, this is a Spanish university study from 2023. They found shell pieces from the brown crab species in caves in what's now Portugal. And it might be the oldest evidence of humans eating shellfish. It goes back a long way. Nice. And I guess it's stretching it even calling Neanderthals humans. This is a very, very old practice for species like us. a very, very old practice for species like us. Yeah, they're our cousins. And we do have some Neanderthal DNA because there was a little bit of hanky-panky between our, like, you know, Homo sapiens and Neanderthals. So, you know, they're not like our ancestors in the sense of, like, humans did not evolve from Neanderthals, but we coexisted at a point and we were evolutionary cousins.

We've got some Neanderthal DNA. Good for us. Good for us. And good for them. Our cousins ate them and we probably ate them too. Yeah. This topic is global. Crabs are in all of the world's oceans.

They're also in freshwater, also in brackish water, and then there are land species. And so we just think that all early human communities ate crabs if that was convenient. Like they weren't going long distances to do it, but it's an easier and safer source of protein to hunt than many other animals. And so anybody living near a place where crabs live probably ate them. near a place where crabs live, probably ate them. Yeah. It's just, they're so pinchy. I wonder like at what point did we get beyond the pinch and the spindliness and realize that there was meat in them bones? Yeah. Possibly 90,000 years ago or more. Like good for us. That's kind of a, I feel like that's a big insight if you don't know anything yet. You know what I mean? Like, that's a pretty good leap. That's pretty good work.

I wonder if we just ate them raw or if we cooked them. Probably started off eating them raw, but ugh. Ugh. Right, like just grabbing it like it's a weird bagel. Like, ow. Just, you know? Yeah. Like, this bagel keeps pinching my face.

The world's first brioche. You're pinching my face. The world's first brioche. And then one more number for the numbers section, jumping much closer to our time. It's the year 1956. 1956 is when an American medical researcher discovered that horseshoe crab blood contains a useful component for testing drugs and vaccines. It's also an eerie shade of blue, which is interesting. And it's blue.

It's blue. Yeah, no, we have horseshoe crabs to thank for a lot of our vaccine production. Yeah, it turns out. And we just kind of didn't have that help before. There was an American medical researcher named Frederick Bang. He discovered that horseshoe crab blood has amoebocytes. If a drug or vaccine has been contaminated with a kind of bacteria called an endotoxin, the amoebocytes in horseshoe crab blood will react to that and form solid masses and make it obvious to us that that contaminant's there. And the US FDA approved using that in 1977. Europe approved a synthetic version in 2016,

but the US hasn't. And for several decades, we've been using many, many gallons of harvested horseshoe crab blood to test all kinds of drugs and vaccines. And it was a key part of COVID vaccines. Yeah. I mean, it's one of those things where they actually don't have to kill the horseshoe crabs to get the blood. They can harvest the blood from the crabs. The problem is if you harvest blood from a crab, a horseshoe crab, and then release it, it actually does impact its chance of survival and chance of reproduction. You know, I mean, imagine if a, like if a Dracula just sucked a bunch of your blood, you're not immediately going to have the energy to go out and hook up or take care of yourself. You might just like keel over and die.

like keel over and die. But, you know, so it is, I think it is a good thing to switch to a synthetic version as long as it's doing the same job as the horseshoe crab blood. But yeah, I mean, until we do that, it is very important to make vaccines really safe to check for any kind of impurities. Yeah. And there's, especially on the east coast of the US, a lot of capture of horseshoe crabs, draining of their blood. And early in this process, we thought it was totally fine. They thought only about 3% of them proceeded to die from this experience. And further studies said it's more like 30%. So conservation groups are now trying to kind of push for a more sustainable approach to this and we'll see if technology can replace it. But we'll link National Geographic. They have a picture of a facility where a row of horseshoe crabs are having blood removed into these like containers of blue blood. It's pretty dystopian if you sympathize with the horseshoe crabs.

It's pretty dystopian if you sympathize with the horseshoe crabs. Yeah, it's very the other side of the matrix. So sorry, guys. Maybe we should call them crab scenes instead of vaccines. Actually, like vaccine comes from the word cow, vacca, because of how the early development of vaccines through the cowpox virus, inoculating people against smallpox. That's so cool. Wow.

In Italian, the word for cow and vaccine is the same thing, vaccino. Good for Italian making it really clear, right? Yeah. Don't lose track of that heritage. But it is confusing sometimes because like I'm here for my flu vaccine and then they just give me a sick cow. Right.

And then you have to walk at home. You have to find a bell. Always need a bell per cow, you know? Jeez. Yeah. The amount of tissues a sick cow goes through is a lot. There's a couple more takeaways for this main episode, and the next one is takeaway number two. Many hermit crabs choose to turn human trash into homes, especially plastic trash.

Yeah, this is both sad and cute. Scoot, scoot, scad. It's so cute. It's scad. It's scad. I'm feeling scad right now. Yeah, maybe the cow wasn't sick. It was just scad, you know?

Maybe it's just emotional. The tissues are for feelings. It's verklempt. Yeah. And the pictures here are astounding. They truly are scad. Yes. I think the one thing most of us know about hermit crabs, even if we haven't owned them like Katie has, is that they live in a shell or another aquatic thing that they find.

and more and more we are discovering, especially thanks to better cameras and the internet, that a lot of hermit crabs are making the best of human junk as something to put on their bodies. Yeah, I mean, part of it is if there's a lot of litter, they're going to use what's around. And part of it is if it's harder to find shells, right, like maybe because of trawling or other sort of issues where there are fewer

shells for them to use, they're going to resort to using litter. Yeah. Hermit crabs really are the progenitors of if it fits, I sits. Like they, as they grow, they don't grow their own shell. So as they grow, they have to replace the shell. And so they climb out of their old shell and then find one that is of the right size. And they can be fairly picky about it, right? Like it can't be too big and it can't be too small. Sometimes there are these chains of crabs where one crab is moving out of its shell. And so like it goes a size up, but then there's like a chain of crabs basically swapping shells, like a big one is going into a bigger shell, so a smaller one is going into the old shell. And so you just have this lineup of crabs all exchanging shells. But like, yeah, no, in this case, they are using bottle caps,

broken light bulbs, a lot of creative sort of things that are vaguely shell-shaped. Probably not as good in terms of actually protecting them, though. Just imagining a crab realtor for like finding apartments. It's really lingering in my head now. Because yeah, they're just making these trades all the time. Apparently they trade every about 12 to 18 months. They'll switch shells or other items. Either they outgrow it or it's damaged or maybe they think there's a more advantageous shell than what they've got.

Yeah. Another problem with like these sort of like, even though it's extremely cute to see a hermit crab using a bottle cap as a shell, even though that in particular doesn't necessarily hurt the crab, there are cases where there's a lot of litter. And so you'll have one hermit crab go inside of like, say, a glass or plastic bottle, because they're checking it out to see if this is like a new home. But then they kind of keep crawling in it. And then they go into the bottle, but the sides are slippery, so it can't get out. And then it dies. And there's this thing that happens when a hermit crab dies is there is a chemical produced during its decomposition that actually signals to other hermit crabs that a hermit crab died. And so

other hermit crabs come to the dead hermit crab to potentially take its old shell, right? Like, well, you're dead. You're not using your shell anymore. I might as well take it if I can smell that you're dead over here. And so you have this cycle of death of hermit crabs that keep crawling into these plastic or glass containers because they smell the other dead crabs. It's like, free house. Oh, no.

Free house. Oh, no. Oh. So then they'll just find these jugs of like dead crabs. It's very morbid and sad. I know it probably doesn't fit like the scientific meaning of the word social, but it's it's a whole community activity kind of thing. Right. Like that's so strange to think about.

It's both. Yeah. Because like they can sometimes compete for shells and stuff, but sometimes it's more cooperative. Like I said, like the shell exchange where it's like, well, if you see a big crab getting out of its old shell, but you're a little smaller than that one, then maybe you take its, its shell and you shed yours. And then maybe a smaller crab takes your old shell. Right? Like, so yeah, in some, it is kind of an interesting sort of social exchange. And the need for a home at all is just so weird too. Hermit crabs basically have two kinds of exoskeleton. Their front half is a hard and tough shell, and then their back half is much softer, designed to flex and accommodate being

placed in a container. They're built to be seeking out these homes. And then because of human refuse, there's more and more useful stuff from people. They don't just have to use the shells of snails or natural items like tree nuts. There are apparently hermit crabs near Okinawa that use tree nuts from that island. But more and more crabs are using, especially bottle caps, also the metal bottoms of light bulbs. Kind of reminds me of like octopus behavior. There are these coconut octopuses who use coconut shells as like temporary shells that they'll carry around with them as protection. Octopuses and squid and stuff, they actually have ancestors that had shells. They're related to nautiluses who have shells.

And like their ancestors used to have sort of like a hard shell, but then they evolved to not have a shell so that they could squeeze into tight places, both in terms of hiding, but also in terms of hunting. both in terms of hiding, but also in terms of hunting. So then like some species of octopus have gone sort of hermit crab style where they like take things like shells or coconuts and then use them to sort of protect their soft bodies while still being able to have sort of the flexibility of having a soft body. Although with hermit crabs, it seems like really it's about the superior protection of the shell versus what they could achieve through their hard exoskeleton. Because like that vulnerable period of a crab's life where they're soft shelled because they are going through shedding their exoskeleton. Now they have like a thing like a shell that permanently protects them, even if they are at a stage where they're vulnerable and shedding their exoskeleton. Yeah, they get to kind of make so many choices. They're not just on the biological cycle. That's cool. It's very cool.

We also know more about this than ever before, thanks to the internet. There's a new Polish university study that was published February 2024, very recently. And they did not send a team out to see. They indexed images in scientific journals, as well as image uploads to Flickr.com, Google Images, iNaturalist, Alamy Stock Photos, and YouTube Thumbnails. And based on that data set, they think plastic is far and away the favorite trash for hermit crabs. They estimate of all trash shells for crabs, about 85% are plastic compared to just 5% metal, 5% glass, and 5% mixed materials. Is that just because there's more abundance of plastic or are they specifically choosing the

plastic? They think it might be both. Yeah. Because there is so much plastic in the ocean. It's a really abundant form of trash. And then also hermit crabs might even prefer plastic in some cases because it's more durable than some shells and also lighter weight than some shells at the same time. We need a crab focus group. We need to really see what products these crabs prefer. You know, that's the other weird thing about the name hermit crab. These crabs clearly hang out all of the time. And we call them hermit crabs like they're some loner in the woods, you know?

They definitely seem like they would be down for a focus group. You know, just like one coffee and donuts in the corner, they're there. Great. One of them is trying to see if they fit inside the donut. Yeah, and then the one other thing is we think some hermit crab species, the shell or whatever they pick up might be involved in sexual signaling and being more attractive to other hermit crabs. And so with plastic being brightly colored or interesting shapes, maybe there's something there.

It's so weird how humans have shaped animals' evolution in such indirect ways sometimes. Yeah, they didn't plan on any of this. And that plastic trash in the ocean is from the last hundred years. It's so recent that they're dealing with this now. It's like how bowerbirds, which are these birds that create these elaborate displays, usually use berries and flowers. But now with human trash around, sometimes they'll pick up some brightly colored human trash and carry it over and use it as part of their mating displays to attract females.

Yeah. Yeah. I am glad they're making the best of that and we should do better and they're making the best of it. And we have one more huge takeaway for this main episode. We'll come to it after a short break and get into some really, really weird human crab stuff. Human crab. Human crab. It sounded like a hybrid being of created. Yeah. We are the human crab people.

We demand little pieces of white stuff that floats in the ocean to eat. Put it on one side of me, not in front of me, not in front of me. That's boring to me. I'm Jesse Thorne. I just don't want to leave a mess. This week on Bullseye, Dan Aykroyd talks to me about the Blues Brothers, Ghostbusters, and his very detailed plans about how he'll spend his afterlife. I think I'm going to roam in a few places, yes. I'm going to manifest and roam. All that and more on the next Bullseye from MaximumFun.org and NPR.

Hello, teachers and faculty. This is Janet Varney. I'm here to remind you that listening to my podcast, The JV Club with Janet Varney, is part of the curriculum for the school year. Learning about the teenage years of such guests as Alison Brie, Vicki Peterson, John Hodgman, and so many more is a valuable and enriching experience, one you have no choice but to embrace because, yes, listening is mandatory. The JV Club with Janet Varney is available every Thursday on Maximum Fun or wherever you get your podcasts. Thank you. And remember, no running in the halls. And we are back with one last giant takeaway for the main episode, because takeaway number three. Because takeaway number three, the names for crabs and for medical cancers come from ancient Greece and from the mythology equivalent of a video game grunt.

What? I didn't comprehend that. Yeah. And grunt is like the lowest level, easiest enemy to beat in a video game. Like you just knock them out easily. Right. Grunt is like the lowest level, easiest enemy to beat in a video game. Like you just knock them out easily. One more time. That's the name for crabs and for medical cancers comes from ancient Greece and from the mythology equivalent of a video game grunt. Right. This gets into the word cancer being, you know, like a zodiac sign that's a crab and the connection between the word crab and the word cancer and all that lore about it.

Yeah, like carcinization being like becoming more crab-like and carcinogenic meaning causing cancer, both being very similar words as well. Yeah. And I had always wondered what's going on there. Why are crabs and cancer? Yeah, the zodiac sign is what got me because it's like, wait, you can have cancer as your zodiac sign? That's morbid. But no, it's like a cute little crab. Yeah, I remember learning that Greek zodiac and thinking, I'm glad I'm not in that month, even though it's fine. It's totally fine.

But like the vibes are off, you know? But it turns out there's a reason why. Yeah, cancer was named after that, not the other way around. Exactly, yeah. Vibes are off, you know? But it turns out there's a reason why. Yeah, cancer was named after that, not the other way around. Exactly, yeah. And there's key sources here are PeaceForSpace.com by Rebecca Sohn, the NPR show Science Friday, hosted by Ira Flato, interviewing medical historian Howard Markle, and then digital resources from Tufts University and from the NASA Chandra X-ray Observatory.

Crabs are called crabs in English because of words in the ancient Greek language with roots in mythology. And the big myth here is the 12 labors of Hercules. This was a whole story cycle in Greek mythology about Hercules doing 12 seemingly impossible things. Like scuttling like a crab was one of them. Like, do it. It's just the gods being mean. Like, now cluck like a chicken. Yeah, so Hercules basically has to do these labors because of his parentage.

Hercules was the son of the god Zeus, who hooked up with a human woman. And Zeus did this constantly, and this upset his wife, the goddess Hera. She was like, that stinks. And also I kind of resent all of the children from these situations. Yeah, she always got her anger out on like either the woman or the children in the affair, which I think is not cool, Hera. Because because I think the common denominator is your husband is a bit of a floozy. Yeah. And this story starts very dark because what happens is Hera says, I just don't like Hercules,

so I'm going to make him lose his mind and kill his wife and children and then snap out of it and feel horrible and sad. Yeah. Like that's, that's, it's one of these really brutal Greek myths. Just like the gods making your lives miserable. And the lesson is sometimes this happens and you can't do anything about it. Right. It's, it's astonishingly dark, right?

You can see how other faiths rolled in, like the Christians. And it's like, that's more positive. I'm in. Cool. Yeah. So then Hercules says, I feel horrible. He asks the Oracle of Delphi how he can atone. And they say, if you do these 12 labors, you'll feel better. And then, so then it's this whole cycle of stories where he's doing these challenges. There are some sympathetic gods helping him and then still opposition from some antagonistic gods like Hera. One labor is to battle the Hydra, which is a huge monster, I think pretty famous. And you like cut off a head and it grows more heads. Is that sort of the idea? Yeah. And so the main story is that Hercules attacks this Hydra and then he needs a friend to burn and cauterize the head stumps in order for him to

cut off the heads and then kill it. And so within that incredibly exciting battle story, Hera says, I'm going to make it harder. And so this character doesn't even get credited as a labor or anything, but she sends in a crab. She's like, go attack Hercules and distract him from the Hydra mid-fight. Do I like, do I like pinch him? You want me to, you want me to pinch him? That would be a good voice for this character because this is the origin of like cancer in the Zodiac and everything. She sends in a crab and the Greeks called him Carcinus. Then that got like Latinized and Anglicized and eventually became cancer. But Carcinus is a crab sent by Hera to attack Hercules in the middle of the Hydra fight. And the crab bites him on the foot and then he immediately just squishes it and moves on. That's how, that's all the crab bites him on the foot and then he immediately just squishes it and moves on. That's all the crab could do.

Okay, I'm just going to pinch you, big fella. All right, I pinched you. Why are you looking at me like that? I just pinched you. Yeah. She told me you got to pinch you. It's a really pathetic kind of thing. It's just a crab that pinches him.

That's it? A normal sized crab? Yeah, like in the story, it doesn't even seem to be very big. Just a normal sized crab. Like it's not bigger than especially the larger species of real crabs. You know, it's just a crab. And then what happens is in the aftermath of this bigger battle, Hera feels bad and says, I'm sorry I really pointlessly sent you in there, Karkinos. I'm going to lift you up into the stars and you'll be part of the Zodiac.

Apologies for wasting your life on a really bad strategy on my part. Bad move. Yeah, no sweat. You know, can I pinch people when I'm made out of stars? Is that something I can do? Because I'm really good at pinching. That's kind of my thing. Just pinching like Capricorn. Capricorn's like, what are you doing? Hey. Pinch. Is that a supernova? I have pinched Scorpio. Wow. I guess there's multiple arthropods in the zodiac. I hadn't thought about that. There is.

Big arthropod scene. I'm a Scorpio. I've done nothing to ever learn about what that's supposed to mean. It's just cool because I like scorpions. Yeah, it's pretty good. Yeah. I'm an Aries. A ram is cool, you know? Yeah, you know? Into it. Cool. So yeah, so I hope that's exciting for people who are astrologically cancers. It's the specific story of a crab. But then how did it go from meaning like this guy that gets squished by Zeus into like the disease cancer.

Because like I would think like cancer would be called the hydra, right? Because like that feels more cancerous where you're chopping off heads and it keeps regrowing. So why did a little crabby dude, why does he get the rap for cancer? Perfect question. And it turns out Greek medical science comes in here. Because not only is Karkinos called this in the myth, that's also a relatively general Greek language word for a crab. So it wasn't a creative name. And what happens is maybe the most famous Greek doctor comes along, a guy called Hippocrates.

Hippocrates. Yeah, he's the guy from the Hippocratic Oath sworn by doctors today. And Hippocrates, he lived around the year 400 BC. He's examining people with tumors, which we don't really understand yet. But he, for some reason, applied the name Carcinus to the tumors. That crab name and crab character name. He says, I'm calling these Carquinos too. Why?

We have theories. Okay. Just a weird guy? All the theories are different synonyms for kooky, crazy, wacky. Like, oh, that's just it? Yeah. But so according to medical historian Howard Markle, it could be because the tumors often felt hard to the touch, sort of like the hard shell of a crab. It also could be a little metaphorical related to crabs having pincers. So the pain of a tumor

attacking us. Another guess is that tumors are stubborn and hard to remove. Oh, like the crab in my armpit. That's the story I think about now. Yeah. Yeah. I guess I'd rather a hermit crab than a tumor. Check your lymph nodes every once in a while, people, because you got them in your armpits, actually. Maybe the crab was checking and it was like, give me a couple hours. I'll make sure it feels okay. Thank you. It feels okay. Thanks, Pinchy couple hours. I'll make sure it feels okay. Thank you.

It feels okay. Thanks, Pinchy. Maybe that was his name, Pinchy. Back then too, people maybe had an experience of a crab latching onto them with a pincer for a while. And so that could be where Hippocrates got this, whatever the reason he sparked a trend. And the next physician here is a Greek person, but in like the Greek province of the Roman Empire, more than 400 years later, a guy named Celsus. He writes a medical encyclopedia where he names tumors cancer, which is the Latinization and eventually Anglicization of carcinose. I feel like it's not fair to, because crabs are cute and they taste good and they do cool things. Whereas cancer is just pretty awful. I feel like we could have chosen a more annoying

animal to name cancer after. Yeah, there is like one more step that seems to cinch it because, of course, we could have moved on from this weird Greek language and mythology connection. But from there, after Celsus and after Hippocrates, there's another Roman doctor named Galen, who's also famous in medical history. He took an actual look at a tumor, like a deceased person's breast tumor. They opened them up and looked at it. And he sees a network of veins leading out of the mass and decides that the way those kind of fan out looks like the legs of a crab pattern. Hmm.

Interesting. And so he says, based on that and the many Greek and Roman doctors before me referencing crabs, let's stick to that. Like, that's a good reason to call it this thing. The other thing Howard Markle points out is that we, in one way, have gone a different way linguistically because the doctors specializing in cancers are not called cancerologists or cancer attritionists. They're called oncologists, right? Yeah, they're called oncologists, which is from a different Greek root. It turns out the Greek word onkos means masses.

Oh, okay. And that might be kind of even a more accurate word. There are many different diseases called cancer. It can be more of a mass than necessarily a tumor, especially if it's benign. And so we did find a not crab way to describe this, but we are kind of sticking with the crab way in most cases. Yeah. Really hard to get rid of that crab. So this character stuck around. In the Zodiac and in disease, we, from Greece to the rest of

the world, have promoted an idea that somehow crabs are involved with this family of human diseases. All because Hera was like, I'm going to throw a crab named Crab at you, Hercules. Right. Like it was so underpowered as an enemy. It didn't even really have an interesting name. Yeah. I choose you, Crab. It's just against a demigod.

I mean, like, is she even trying at that point? It is less interestingly named than the Pokemons that look like crabs. That's true. Right. Hey folks, that's the main episode for this week. Welcome to the outro with fun features for you, such as help remembering this episode with a run back through the big takeaways. Takeaway number one, many arthropod species carcinized. Takeaway number one, many arthropod species carcinized. They separately evolved to match a crab's shape, and then many crab species separately evolved to walk on land. Takeaway number two, many hermit crabs choose to turn human trash into homes, especially plastic trash. Takeaway number three, the names for crabs and medical cancers come from ancient Greece and a myth equivalent of a video game

grunt. Plus so many stats and numbers about the biggest and smallest crabs, crabs in every habitat in the world, the magic of horseshoe crab blood, and more. Those are the takeaways. Also, I said that's the main episode because there is more secretly incredibly fascinating stuff available to you right now if you support this show at MaximumFun.org. Members are the reason this podcast exists. So members get a bonus show every week where we explore one obviously incredibly fascinating story related to the main episode. This week's bonus topic is Amelia Earhart and the evidence for and against her getting eaten by crabs. Visit sifpod.fun for that bonus show, for a library of more than 15 dozen other secretly incredibly fascinating bonus shows, and a catalog of all sorts of

MaxFun bonus shows. It's special audio. It is just for members. Thank you to everybody who backs this podcast operation. Additional fun things, check out our research sources on this episode's page at MaximumFun.org. Key sources this week include the book Walking Sideways, The Remarkable World of Crabs by Judith S. Weiss of Rutgers University Newark, a lot of new studies, in particular 2023 and 2024 university work, and tons more digital resources from National Geographic, NPR, New Scientist Magazine, NASA, and more. That page also features resources such as native-land.ca. I'm using those to acknowledge that I recorded this in Lenape Hokang, the traditional land of the Munsee Lenape people and the Wappinger people, as well as the

Mohican people, Skadagook people, and others. Also, Katie taped this in the country of Italy, and I want to acknowledge that in my location, in many other locations in the Americas and elsewhere, Native people are very much still here. That feels worth doing on each episode, and join the free SIF Discord, where we're sharing stories and resources about Native people and life.

There is a link in this episode's description to join the Discord. We're also talking about this episode on the Discord. And hey, would you like a tip on another episode? Because each week I'm finding you something randomly incredibly fascinating by running all the past episode numbers through a random number generator. This week's pick is episode 155. That's about the topic of ice cream. Fun fact there, the United States and Cuba each tried to become the world leader in ice cream making and ice cream flavors to prove they had the best way of life in the Cold War. So I recommend that episode. I also recommend my co-host Katie Golden's weekly podcast,

Creature Feature, about animals and science and more. If you like this episode at all, you will obviously love Creature Feature. Our theme music is Unbroken Unshaven by the Budos Band. Our show logo is by artist Burton Durand. Special thanks to Chris Souza for audio mastering on this episode. Special thanks to the Beacon Music Factory for taping support. Extra, extra special thanks go to our members and thank you to all our listeners. I'm thrilled to say we will be back next week with more secretly incredibly fascinating So how about that? Talk to you then. Maximum Fun

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