An idea has taken hold of the public imagination. The idea is that nature just keeps inventing crabs. Crabs are just the ideal body plan and are incredibly beneficial. This idea emerged from a review paper that was written during the pandemic by a group of scientists led by doctor Joe Wolf. But the thing is that the idea that sort of emerged into the memo sphere is really quite different than the idea that was initially presented in this
review paper. So today we have doctor Joe Wolf on the show, and she's going to tell you about what we actually know about how often the crab body shape pops up in nature, and what we know about whether or not that crab body plan is beneficial. Welcome to Daniel and Kelly's extraordinarily crabby universe.
Hi. I'm Daniel. I'm a particle physicist, and I'm crabby in the evenings.
Oh. Hi, I'm Kelly wieder Smith. I'm a biologist, and I want to believe I'm not crabby in a like Circadian rhythm sort of way. Maybe never. What is crabby, Daniel?
Like, I've just noticed that between me and my wife, I tend to have more energy in the mornings, and she tends to have more energy in the evenings, which actually has worked out well as parents, because I get up early and I'm ready to go, go, go and get stuff done and help the kids with X Y Z. And when it's like nine pm and the kids you're like, oh, by the way, I need forty five cupcakes for tomorrow, Katrina's like okay, I'll spin that up, or like, let's
go buy these special shoes you need for tomorrow's activity or whatever. So you know, as a team, it worked well. But yeah, I tend to be more tired in the evenings and she tends to be more slow to move in the mornings.
We also have that division. Zach is more of a night person and I'm more of a morning person, and so I'm the one who make sure everybody gets up in the morning and we don't miss school, and Zach is the one who when the kids are kind of dragging their feet, he makes sure they get into bed because I'm a zombie.
Isn't it funny how to get together you have to have sort of those rhythms in common. But then to survive as a parent, it's better to actually have the opposite routines.
I mean for us, Like when I was younger, I could roll with it, like I'd rather not stay up late, but okay, final I'll stay up late. And even if I have to get up early, I can do that too, because I'm young and I can do anything. But now like I can't deny my daily rhythm anymore.
Well, I think that leads to the obvious and deep question, which is when are crabs crabby? Do they tend to be energetic in the mornings or what? Or crabs just crabby all the time.
I don't know. Probably depends on if you're harassing them or not. They're probably crabby whenever you know, young kids are trying to pick them up.
They just want to be crabs, man.
Yeah, just let them be crabs. And speaking of crabs have been sort of all over social media since the pandemic, and there's this idea that the optimal form for organisms is the crabby shape. And so we had this great question from a listener, and let's go ahead and listen to that question.
Now, Hi, Kelly and Daniel, listen, what's the deal with crabs? Why does nature keep reinventing them? Can we get a new blueprint, maybe something with wings, crab wings. Anyway, I'd love to know why some of Nature's designs get recycled. Thanks, guys love the show.
So it turns out that I happen to know doctor Wolf, who is one of the people who wrote the review paper from which this Crabby Body Shapes meme emerged from, and she's a little bit frustrated with how it has sort of taken off in a sort of inaccurate way, and so I invited her onto the show to give us all the details of what we know about this question and to sort of talk about how this idea took off and went off in weird directions.
It's amazing that you know so many influential, famous scientists, Kelly.
I've just harassed a lot of people throughout my life, I think, for various projects, and they've all just been nice enough to keep talking to me.
That's wonderful. Well, it's really great to see friends succeed.
It is, yes, right, and Joe is at Harvard, which is incredible, and so let's go ahead and start that interview. Doctor Joe Wolf is a research associate in organismic and evolutionary biology at Harvard. Welcome to the show. Joe. Hi, I'm so excited to have you here. And my husband I've been talking to him. I was like, Oh, we're going to ruin the crab thing, and he's like, Oh, you're gonna do the what planket thing, which is like what he's sort of, you know, come to know me for.
But anyway, so let's jump right in. So when you hear folks say stuff like nature keeps inventing crabs, what do they mean? And what are the crabby features that are being honed in on?
Here, I'll answer the part about what the crabby features are. I suppose this is something that's been and observed several times within a group called decorpod crustaceans. So decor pods contain probably the most crustaceans that most people are familiar with, crabs as well as shrimps and lobsters. And what we think that we understand when we see a crab, like, everyone has an image of what they imagine, and that
is something that has a flat and wide carapace. Usually it's kind of oval around shaped, right, and generally the only thing that you see sticking out are legs and cloths so unlike with a lobster, where it has like this long abdomen and a tail fan sticking out, crabs don't visibly have that. It turns out that they do have the abdomen, but it's actually folded underneath the body.
So the folding that is kind of one of the other major crabby features, and it actually covers up the underbelly, if you will.
So the thing that makes something crabby are a flat carapace and then eight legs. Basically no, no, all right.
Technically they do all have eight legs, but some of them do not have eight visible legs, and some of them that back there is super tiny, and sometimes it's in a specified chamber where you couldn't see them.
Wow, all right, what are they doing in there?
They're like cleaning some of the more sensitive anatomy.
Huh yeah, okay, I didn't know that. Cool.
Well, I wish I had special invisible legs to clean my sensitive anatomy.
Yeah. So this is actually one of the main differences. So the idea that a crab like form has evolved multiple times has been known for over one hundred and forty years. And if we think about the tree of life, right, so This is like how different species are related. It's a bigger, an older version of the same thing as us having a family tree. So in the crustacean family tree, there are two groups which are each other's closest relative. One group is called the true crabs and one group
is called false crabs. And so, Daniel, what you actually mentioned is one of the main obvious ways to distinguish them. True crab eight legs, false crab technically eight, but you will only see six usually or less. Permit crabs are part of that, and they usually only look like they have four because actually the back two pairs are involved in holding onto the show.
And is that an arbitrary labeled true crab and false crab? Is there something just truer about one of them or is there like a value judgment there or is it like the remnants of an ancient argument among friends or what.
No, it's a colloquialism. They have Latin names, So true crabs with brack eura and false crab with animura, and that actually refers to basically the folded under ab.
It's really weird when you see an animal that's described basically about what it's not.
You know, well, I think it's because within the false crabs you see something that looks like a crab, but they're not within the same group. So what that means intert of the family tree is that the ancestral form, or at least what we assume to be the ancestral form. And definitely many of the forms within the enemure or false crabs, many of those are elongate and they look
more like a lobster. So some of them look like crabby and oval, and some of them look wrong and have like this abdominent tail and the tail fan like a lobster, which crabs don't have.
Well, I'm feeling for the false crabs because I'm often described by my teenager's friends as like Hazel's dad or signs of the dad. I'm just like to find a relation to somebody.
Else, something better.
Yeah, exactly, something better. That's the implication right there, And so feeling for these false crabs. I'm on the false crabs team over here.
They're actually my favorite, so.
They're your favorite too. Yeah, there we go. The downtroden exactly, the crab crushed under the foot of evolution.
They do have fewer species, so the true crops they have at least seventy five hundred described species, and the false crabs have like twenty five hundred. I'm saying described because we don't know their true.
Diversity, and so you're talking about the various shapes of these critters today, and then you're also talking about the family tree. What is the relationship between these things? Is their common ancestor also krabby or did they evolve crabbiness independently? How many times has nature like invented crabs.
So they did evolve it separately. It's challenging because we don't know what their exact ancestral look like. In order to be able to do that, we would ideally have many many fossils that came from the oldest point as close to the divergence of those groups possible. They do have a pretty good fossil record, but a lot of
the fossils are just the care pace. And the reason for that is if you think about what happens to a quarks, Basically, if you throw it in the water, you know the parts that can fall apart will fall apart or be scavenged. So pretty much what happened to them is that. And so if you only have the care pace. Upon is that we already know that things that look similar in this group might not be both relatives. We know that from modern groups whose DNA that we have.
So if we see something that looks similar and it's only the care pace, we can't always be certain in the fossil record, so that's kind of why we don't know what their exact ancestors are. However, we can look at least within the living groups at what their closest relatives are, and that can kind of help. And so within both the true and crabs we see krabby and not so krabby forms. So actually what we see is within the true crabs. Probably there's two instances where the
Krabby form has evolved. One is in a pretty small group, which is kind of what we call the out group to the rest, So that means that basically the first branch that evolved from the true crabs. Within that group, we see one set of sort of rounded little guys that look like craps, and these are called the sponge crabs. They're called that because they usually make a hat out of a sponge and they wear it.
Oh that's so cute. I have a new favorite crab.
Now, why do they make a hat out of a sponge?
Well, I guess it makes good camouflage if you look like an inanimate object a living thing, but nonetheless, hopefully no one's gonna come ool with you.
Right, Do we have any tests to see if that actually works, like if you take their sponges off or you give them a better sponge. Has anyone actually shown.
I don't know. I know I've seen some videos of people making like out of kitchen sponges and seeing how the crabs because they kind of like cut them up a little bit of their claws so they can do that, But I don't know if anyone's published a systematic test of that. There are other groups that hold things on top of themselves, like a hat. Hermit crabs technically are kind of doing that, so they shove their back end into it too.
I love that they're like cutting their hats to fit the way that they want it. Anyway, this is very exciting. I could talk about this for five hours, but maybe we should keep going.
Right, So that's the first group, and then the other group from the true crabs is there isn't a good common name for but it's the majority of true crab diversity, and I guess they can be called the higher true crabs, although that's a value judgment, and it's just referring to the fact that they share a common ancestor amongst themselves. So the vast majority of true crab species fit inside that.
So that's like spider crabs, swimming crabs, decorator crabs, pretty much all land crabs, most of the ones that people eat, those are all within the higher true crabs or you breck eree, So those guys are almost all having the crapit for.
And when we talk about this history, is this recent history, like this stuff has evolved in the last ten thousand years, one hundred thousand years. Are we talking hundreds of millions of years or what's the timescale?
It's hundreds of millions, Yes, it's quite old. These guys were and off pretty much around the time of the dinosaurs. So if a dinosaur went for a swim, then they might have encountered some crabs. Even there were some crabs starting to go at least into brackish water environments also at that time, so they could have met up.
I have the impression when I hear about a species that hasn't changed in hundreds of millions of years. That has sort of reached some plateau where like you can't really improve very much. Is that totally falls And it's just that the time scales so long, like in a billion years, crabs will look different, or have we somehow found some niche where it's really not going to change much more.
That doesn't actually describe crabs, it's a term used to describe horseshoe crabs. So I guess we've got to address that. Elephant and horsy crabs are not a crustacean unfortunately.
Oh wow, they're false false crabs.
Right, yeah, yeah, they are. They're pretty much like interactive like spiders and scorpions, and the way that we distinguish different groups among arthropods. So archipods first of all, are the animals that have jointed legs. So within the horseshoe crabs and iraqeids those guys versus crustaceans, it's basically the number of segments of their head that is the main morphological way that they were first identified. And DNA data
also verifies that these are separate groups. So they are at least five hundred million years different so horseshoe crabs Also, although they are around it, they don't have the same body parts as a crustacean, So they don't have this abdomen that folds up underneath. When you imagine a crab, it's not like this little taper bit and then a long spine at the end. Right, there's like a middle
piece that crustaceans have that they don't have. So they're a little similar, but I wouldn't personally describe them as having the Krabby forma. Some people have said that they do if they're trying to make a really really broad ecological argument. People have also said that rais, you know, like the sting rays, that they're like that too. Of
course those are vertebrates, so that's really different. So yeah, if you want to get really broad, then there's a lot more examples, but none of them have the abdomen folding up, which is one of the features that I think is really important.
But you brought up horseshoe crabs because they have sort of stabilized on long terms and you don't expect them to evolve.
Or here's the thing, they have been evolving the whole time. Their morphologies are similar to fossils, But when we study the DNA, they have been changing the whole time. So the morphology what we see visually seems the same, but they've been change so evolution has proceeded. I guess morphologically maybe they are very suitable for life through a lot of changes in the world, which is great. But no, it's kind of a fallacy that they haven't changed.
Well, it would make more sense for evolution to be constant, right, I mean the environment keeps shifting, right. Earth is not the same, the climate is not the same, the other critters crawling around the Earth are not the same, so it makes sense for things to continue. I always thought that was weird. So you're telling me the things are constantly evolving, And so the idea that like crabs have reached some final form is a misunderstanding.
It is. Yeah, so even within like the crustacean crabs, the deck pods, so true in false crabs, to say that they haven't changed even since the fossils, that's completely untrue. Actually, they have huge rphological variety. Why there are so many species. The horses youp grabually have four living species. But I just told you that there's like eleven thousand living species of crabs, and then there's also thousands of fossil species as well that are no longer a lot, so they
have actually changed a lot. But it's true that there are examples of organisms like the horship crowd that haven't changed that much morphologically. So yeah, the true crabs as well as the false crabs, they have been morphologically changing as well in response to changes in their environment and so on.
And I'm going to pull us back a little bit. So Daniel had asked you how many times nature invented crabs?
Right, I got to two of them, right, So the.
Sponge crabs and the higher true crabs are two examples.
So now we got to switch over to the false crabs, which are Maya Daniel's favor. So those guys, they have at least instances, and the probably the oldest instance is what's called porcelain crabs. Those guys are little filter feeders and they live mostly in core reefs or intertidle zones. So if anyone lives near a beach, which in Irvine you probably do, we definitely do, you could probably see them. I went in a tide poole there I have definitely
seen them in southern California. So they'll look like a crab, but count the number of legs and then you'll see they're pretty small too.
We go to the tide pools all the time, but we try not to disturb the little critters because I feel like if everybody comes and like picks up a critter, then we're just going to be like wiping out some population.
I think that probably is a safe bet. I wouldn't recommend handling animals in the wild if you aren't going to be very gentle. Obviously I have to do so because I have to collect them for work. We can't get the DNA if we don't capture and I'm sorry kill them, I know. I mean, I'm a vegetarian, so like I won't even a crab. I've never eaten a crab in my life.
Oh my gosh. Even the ones that you capture and kill for their DNA, well, you.
Got to put them in preservatives. So actually a lot of them we do put in ethanol. So yeah, that would be like making an alcoholic beverage.
But crab cocktail.
That would be disgusting. Like if you actually open some of these vials, I know Kelly has done this, Like, uh, you know, a little one is fine, but like some are really big or like even giant squids are nothing. You open them up, you can pretty much get high off the fumes.
Yeah, and you know that Kelly has done this.
Is that what? Yeah?
Oh yeah, Kelly has snorted squid fumes. Wow, that is something I've learned about Kelly today.
Well I've done it too.
It wasn't squid fumes, it was large quantities of preserved fish vomit. But yes, you do get a little bit sort of high sitting around these samples.
What does that go for on the street, Kelly.
Nobody wants it. Actually, it turns out.
Price is zero.
There were some samples that we did for one of my projects that we had to dissect and we got them from like the fish market. So actually my colleagues ate the parts that I didn't dissect. I had to dissect them, but I didn't look at it. So yeah, so you can't eat force and the crabs though they're really small. But the other main one within the false crabs, lots of people eat that's king crabs. So like Alaska king crab that's really famous. That's not truly a crab.
It's false crap. Count the number of legs.
Not truly a crab. Oh my gosh. Yeah, taste pretty crabby.
Yeah yeah. So those guys, they live pretty much white bold waters. So the only way people are going to encounter them without going out in a boat is if you're in pretty much quite cold places, so like the Pacific Northwest. I would say southern California. There might be a few, but they're more common furthermore, so that's why, like Alaska is one of their hot spots.
They've got their own TV show.
I don't know if we're just whims, but the water's pretty cold hair in southern California.
Oh well, I am from Canada, so.
Do you call me a whim? That's why I live here?
Yeah. Yeah. So then there's the third group within that false crabs, and I hesitate to quality group because there's actually only one species, which is the only species in his family, so it's just weird. And it's this one species called lomas Herca is the Latin name. The nickname of it is the harry Stone crab, and it's ecology is pretty similar to porcelain crabs. They're in the enter title zone, but it only lives in southern Australia and its claws look like giant mittens. I was supposed to
go to a conference in Brazil in twenty twenty. Of course that happened to the pandemic. But one thing I was told is that at resilient conferences sometimes there's costume parties. So I was planning to make giant mittens and wear them on my hands to be this crab.
See there are some biologists that are fun at parties.
Yeah, yeah, I don't know if people would think that would fun, but you know my colleagues would ever. So it's got that, and then the rest of it's kind of camouflage to look like it's covered in algae and it's brown, and then randomly it's got like these bright blue antennae.
It doesn't sound like it would help with camouflage.
No, I don't know what's up with that. It's not super well known. So I actually did get a chance to see this species in Tasmania. I went there a little before the pandemic and I pretty much went with the express purpose of finding this crab. So I'm texting my collaborators, I'm like, oh, I'm going to find it. I'm going to find it. And it was like, you know, because of the intertitle, you can only look for a couple hours a day because the rest of the time
it's covered in water. It was like the last day before I found them, I was kind of freaking out. I was like, oh no, I came all this way and I didn't and we got to them.
And what does it look like on the Crab Researcher group chat when you finally find this elusive crab?
Well, we actually named the crab Researcher group chat to I saw lo miss. I still call that years later. Our chat is actually still called that.
I love these little revealing elements of nerd culture, you know. Yeah, there was a great moment when I made the scientific discovery, and then there was an even better moment when I gloated about it in the group chat.
So true.
Well, we're all happy for our friends when they find the thing that they've been looking for.
Yes, absolutely absolutely shared joy.
Anyway, it got meiled back to the US to my colleague in Miami, and eventually she extracted DNA from it. We got our data very nice.
Yes, awesome. Yeah, Okay, so we have established that as far as we know right now, nature has quote invented crabs five times. And when we get back from the break, we're going to find out if five is a big number or a little number. And we're back. So Joe told us that nature has invented crabs five times. If you go on social media, you would think that nature is just like constantly inventing crabs. Whatever that means. Should we feel like five is a big number or is
five a like little number? In terms of nature inventing things, I think.
It's a bit of a Goldilocks situation. So basically convergent evolution where you see similar traits evolved multiple times in different unrelated groups. This is actually pervasive. So one quite famous example is echolocation, where both That's and Wales have both people, so that's two times, and a lot of
the examples are two times. But there's also a lot of examples that have a ton of times, so like bioluminescence or having venom, those have evolved like one hundred times, so there can be some that are quite a lot.
I think though, that there's something that makes crabs being five times particularly interesting, and it's kind of because it's not just the number of times, but you have to think how long is the period of time in which that's happened, Right, So crabs common ancestor between the true and false crabs is something like three hundred million years ago. So five times within.
Three hundred million years is actually pretty good, whereas bar the un essence being one hundred times, and so that's including all of life, like even back to here to have violins, So that's billions of years.
So we need to consider like the denominator like out of how many possibilities, and we need to consider the time span, like how many opportunities are there exactly, And so you're saying five is actually not that big a number, Well.
It's not that big a number, but it's also not that small. So there are some other groups that are much more recently involved, that have more groups. But one thing that I think is interesting is that in many of those they're so recent that there's not that much
variation in them to begin this. So, like one famous group that's a model for studying competant evolution is a group of lizards called annals or anolus, and they live in the neotropics and on different islands within the Caribbean, they have repeatedly basically colonized to the islands and evolved multiple what's called eco types. So there's animals that live on the ground, there's animals that live on tree and
higher up in the tree. Something like that need happen multiple times every major island, so like four times at least, probably more. And the thing is, though they can't do much else other than that, they're always going to keep doing that every island that they go to. I'm simplifying it, but perhaps there is so much variation. So even though we see the same base form with the flattened carapace and the folded up happening multiple times, within that, there's
a lot of variety. They have spikes or not spikes, the shape and length of their legs and claws, all of this is completely changed many many times. So it's kind of a good example in that regard too, because when we want to understand evolutionary process, at least to me, the reason to understand this is because we want to explain variation. You can do things with analysts like experiments.
You can move them from one island to another and then see what are going to do much harder to crabs, but you know, we don't know what we're going to get either necessarily perhaps, so it's kind of fun.
If this is an intermediate example of how often this kind of stuff happens. What are your thoughts on why everybody thinks nature invented crabs? Why is this the example that like just took off and took over the internet?
So in the paper, and I think the oversimplified explanation is that we often talk about potential adaptations because the assumption is that convergent evolution is a case where an organism has faced with the same environmental challenge and so it's going to solve that challenge in the same way.
So the two main ideas for this to adapt to are either being best able to escape from predators, either by running away, or also because when you're folded up, you're potentially a smaller target to be grabbed, I suppose. I guess, like just think about if you're trying to grab a crow versus if you're trying to grab a lobster. There's a back end on the lobster and there isn't on a crap, right, So that's one and then the other idea is that it improves their locomotion, so like
crabs can walk sideways. I think it's more complicated than that because some of the groups within, even in the false crabs that don't have this folded up body, they can sort of jet backwards, sort of swimming like, and this is called like the tail flip escape reaction. It's got fancy name, but it's just jetting backwards. And crabs can't do that anymore when they fold up. They need the tail to do that so they can escape in a different way. I don't know which one is better.
I think in science what we usually want to do is we want to know if something is affecting an outcome, we would have to do an experiment on it. And there are biomechanical studies on how crabs walk, but none of them are comparative, so there's no control you need to look at. Is it a better performance at locomotion or predator avoidance under the same conditions as a not said crappy body and nobody has done that yet.
People keep saying nature invents crabs because that's great, but we don't even really have great evidence that the crab body shape is superior to other body shapes.
We don't know that. I mean, I wouldn't be surprised if some of this was contributing to them, but it may not be. We just don't have what I would say is really strong evidence, and I wrote that in this paper, but well, we'll get to that later.
I found it fascinating how different branches of science have different abilities to sort of control the experiments. You know, like in particle physics we can manipulate our experiments completely. Astrophysics they just sort of watch what the universe does and hope that it does something interesting that reveals some thing here. You have some opportunities to like influence, but you're not completely in control. But say you were somehow you know God or could control the universe, how would
you set up the experiment to answer this question? How would you definitively prove whether crabs are a good outcome or not.
You have to have the hypothesis of what their outcome is improving. So say you have the hypothesis that it's going to make them that are at escaping from a predator. Right, So you set up sets of tanks and you put a bunch of crabby bodies in one set of tanks, and you put a bunch of long boys in the other set of tanks, and then you put like a big scary fish in every single one.
Long boy is not a sandwich, right, a sandwich.
To me, sorry, I mean like squat lobsters or something.
Then I'm thinking, like, you know, I'll have a long boy. Hold the olive oil, please.
But all right, I think people do eat some of the squat lobsters actually, like in the Mediterranean.
Yeah, everything's in delicacy somewhere, right, fish vomit is like very prized in the streets of some city around the world.
Exactly.
I'm not sure about that one.
But all right, to get back to your crabby versus long boy experience, I.
Yes, So then you put like a fish in there or I don't know, something that you know will predate upon them big scrap. You have a big tank because you're gone, right, So you have a really big tank and the only thing in it is the crab, and you maybe give them some rocks to hide in or not. Some will have rocks, some will have not maybe, and you basically see what happens and how many times the fish is going to catch the crab versus the elongated body form. And so this could be one example of
doing an experiment like that. If they survive, then I guess natural selection has turned out in their favor. If they die, if they don't get to reproduce, so they've been lifings.
Do we need to think even bigger though? I mean somebody could say, well, that's survival in your lab in an aquarium. Really the metric is like, have you survived on the planet. So when you need to like create one hundred or one thousand, duplicate Earth's branch evolution from the same point or something, and like see whether you get more fewer crabs on these planets? Like what is the real test? Like infinite resources here?
This isn't specific to crabs, but there is something called the game of life, and it's a simulation to evolve. It's not like specific forms, but it's basically like little ask you guys or something.
It's a little cellular automata.
Yeah yeah, okay, so you know, yeah.
Yeah, it's famous in programming circles.
I would say that's actually the infinite resources explanation. It's not going to tell you isn't crabs specifically, but maybe you could add like a new package this programming thing it was invented like twenty or thirty years ago. Maybe make it a little more sophisticated now specifically crabby. Maybe there's a way to do this as a simulation.
Well, that's fascinating you bring that up, because in the game of life, they've observed these self sustaining little systems. And for those of you who aren't familiar, there's like very simple rules about whether a cell has something in it or not, whether it eats something or moves or whatever. And there are these emergent structures that people have discovered,
and some of them they call a crab. In this case, it's called the diagonal spaceship sort of looks a little crabby, And I don't know if it really would qualify as a crab or a false crab, or as a digital crab or whatever, or if it's just sort of inspired by this, you know, sort of concept out there that everything turns into a crab. So I don't know if it's evidence or if it just shows us the pervasive nature of the idea.
I'm sure they didn't know about it, because until my paper and the associated work became famous recently, This wasn't known outside of like plustation systematic circles, so they probably saw it and thought it looked like a crab. I didn't actually know that part about it, so I'm going to have to check that out. Very cool.
Yeah, So to pull ourselves back to the real world and out of the virtual world, we've talked about instances where you know you're working through the tree of life and the Krabby body form shows up. Do we see instances where the Krabby body form has shown up and then you lose it? Do we go in the other direction?
Yes? Indeed we've seen this at least seven times, probably more than that, because there's a lot of shape variation. And the reason why this is possible is because of something called trade offs. So one trade can increase in Orban's fitness, and potentially the Krabby body can do this, but it might be decreasing the fitness of other traits.
So depending on what happens in their environment, what's the balance, right, So there might be something else that's overcoming an adaptive advantage of being crabby, and I don't think there's something that's universally the case for these what we call decarsonizations. It's a pretty stupid name, but that's what we call it.
Sounds like you're getting rid of cancer.
Oh my god. So the actual name of crabs was originally called cancer, and the term cancer for the human disease actually came from crabs because the Latin name of craps is cancer, and the original medical doctors who saw tumors thought, oh, this like thing is branching inside of you. It's psycho crab. So yeah, huh, it's actually the same.
Oh interesting. Well, I think the anomology is really fascinating also because we've been using the phrase getting crabby, which to me, you know, has all these implications like I'm krabby in the morning without my coffee, or you know, my husband gets crabby and I cook too much eggplant or something. Do you know where that comes from? I mean, I know that's totally not your field.
Well, I mean anyone's field. So actually, funny story. I spent I would say a lot of years of my childhood kind of being a little afraid of crabs because
I want to be very virild. Just when I was a kid and I went to the Vancouver Aquarium and my parents were filming me with like this ancient video camera VHS all of that O young and yeah, and I'm standing in front of the tidepool tank talking about it, and I pick up the dungeons crab and I'm talking and it's biting me and boom, what is hurting everywhere? So I decided that crabs were my enemy. So I think it's all about how you approached them. That crab
was crabby. It did not like being grabbed by a child.
Fair enough, But why does krabby even have a negative connotation? I mean, it's the same with fishy, like something's getting fishy, but you know other things are neutral, like there's no meaning to I'm getting sharky or you know, I'm getting squiddy.
There is sharky like shark tank right, like, oh yeah, untrustworthy? Are sharks right?
All right? Interesting?
I don't know why we use marine organisms as metaphors for negative emotions. That's kind of weird. Maybe we should all be compared to seals, where we're just like laying there chilling. That'd be nice.
That's a vibe I can get behind.
Yeah, yeah, I.
Think it's amazing that you decided to study crabs after having that experience rather than running away from them, and that you advertise the existence of this video, which now we have to see.
Oh, I don't think it's digitized. My parents might have a copy somewhere, but I don't know if it's in a format that can be viewed anymore.
That should be on your website. I mean, if you're a crab researcher and you have this formative moment.
Man, yeah, I should find out if I can. But you know, I think it's because I actually didn't really understand the difference between true and false crafts. But maybe I did somehow understand it because I never stopped loving hermit crafts. I thought they were wonderful, And when I've got older and started studying arthropod evolution, I kind of figured out that they were related. But yeah, hermit crabs never fell out of my heart. I love them.
They also have a special place in my heart because I grew up near Atlantic City, and so every time we'd go to Atlantic City, you had to come home with some hermit crab pets and take the best care. And probably that was not good for the hermit crabs.
I did some really bad things too, So I grew up in Toronto, which is as far away from the ocean as you can possibly be, so I had very limited chances to see any of these things. But when I was a kid, I guess pre aquarian incident. We did used to go to get caught a few times and I was colecting. You know, the typical kid gets bucket grabs whatever organisms, which I guess maybe Daniel, you don't do that with I did that. I was always
grabbing them and putting them in a bucket. And there was one case where I had like a blue crab, like a swimming crab, and I put fishes in the bucket with it and brought it back to like the cottage that we stared at, and then it was just like the crab ate all the fish heads and left their bodies.
I think every biologist has a story about how they learned about the cruelty of nature in an embarrassing or you know, not ideal way when they brought some animals into their homes.
Exactly at least there wasn't our home.
Yeah, yeah, I've got some stories too, but I brought it into my home. But let's take another break, and when we get back we'll talk about if nature ever invents crabs for reasons that are like random and not so good, and we're back. Okay, So we've talked about how, as far as we know right now, the crab shape has popped up five times in the tree of life and has been lost seven times in the tree of life.
For those five instances where the crab body shape popped up, are those all because it was been official or do you sometimes get like a big morphological change for reasons that aren't beneficial.
Yeah, this is something that isn't that commonly discussed in the public. But indeed, all traits don't necessarily evolve for a reason, or at least not for a direct reason. I would say, they're not all necessarily representing an adaptation.
So an adaptation is going to be the case where individuals that have the trait where it improves this organism's function within its environment or whatever, so like making better at avoiding creditors and so on, then you will survive because natural selection is going to let things die that don't have this trait that benefits you. But parsonization, you know, first of all, we don't know if it evolved in the same kinds of environments every time, so it's tricky
to guess whether this was always the case. So there's one term from biological literature called exceptation, and this is a case where a trait improves the organism's function and the environment where they live now, but the conditions where evolved were different. I think king crabs and hermit crabs are an example of this, So king crabs actually evolved from within hermit crabs. There's still hermit crabs too, but
king crabs are parting them. So at some point in their history they had to get rid of the shell. The shell for the hermit crab is really important, right because they have like this long soft abdomen that could easily and immediately be eaten, and so the shell makes them safe. But somewhere they had to lose them. So what happened there They didn't like immediately get a mutation that made them totally hard and fold it up. There
was some intermediate situation. So one thing that we suggested the paper, and actually that has also been suggested prior to us, is that maybe there was an environmental situation where there just weren't shelves available and they were there already, so they had to do something or die and probably
a lot of the gut. Maybe that's what happened, and that would be a case of an exactation didn't evolve for the reason that we know now, But there was a reason then, and we don't know, because the fossil record, particularly for hermit craps is pretty bad. Them being soft or does not help.
Yeah, now that always makes fossil stuff.
It does, So that's one possibility. There's another possibility that I'm pretty interested in and curious about. Sometimes we have selection on a trait that isn't the one that you're interested in, and maybe that trait is correlated in the genome or in the process of development to the trait that you're interested in. It maybe being crabby is actually related to something else that selection is acting on that we can't see, especially if it's in the genome. We
don't know very much about their genomes. Only a few species have been sequenced, maybe like ten or something, and that's only in the past couple of years. But two years ago there was.
Like one why is it is it hard to sequence crab DNA?
Well, we have lots of pieces of DNA, but sequencing the whole genome the technology to assemble genomes for which you don't have like a detailed reference has only become possible.
Really in the past couple of years. It was expensive and technically difficult, and to spend that kind of money to do it, not a lot of people were going to pay for that. So yeah, it's recently become less expensive, and the software to do it has become easier, as well as the actual sequencing technology, because one of the things when you're sequencing a genome is you're actually sequencing arts like little pieces of DNA, and you have to
using software. And that's why I said assembly. You kind of making the puzzle at the moment, and so if you don't have enough overlap of those pieces, you don't know what you've done. So the technology to do that has advanced a lot recently, So it's possible now that it wasn't before.
So given that we're just at this point now where we're starting to acquire genomes and you know, maybe we could discover some more fossils. Like if we were to have you back on the show in twenty years, how likely do you think it is that the number for you know, carsonization would be five and decarcinization would be seven. Like, how likely do you think these numbers are to change over time?
Well, I definitely think that sampling more species will change those numbers, and it will increase both of them, because we are largely making generalizations. And for me, because I didn't start out as a crab scientist, I mean, I guess I've been doing it for a few years now. My background was in other crustaceans before, so as I keep learning more, I start seeing more variation in their shapes.
And one of the things here that we're also kind of obscuring is we're talking about it like you're a crab or you're not a crab, and I don't think it's very discreet. There's a continuum, like you can have some of the features but not all of it, especially since you're talking about something like a shape. A shape is like, you know, think about it like a vector graphic. A vector graphic for a really detailed polygon with a ton of little sides. If you zoom out far enough,
it looks like a circle. So something like that is going on with these shapes too. They at different levels of study could look more and less similar. So I think we just need to have more species sampled and to study them in very sophisticated.
So we've established that five is like a pretty big number given the amount of time we've been talking about, But evolving the crab shape five times is not a huge number, and it's been lost more times than it has been you know, found by nature. And there's tons of stuff that we don't know. And so what are your thoughts on how this idea became just like the go to idea for like what nature wants to make out of organisms.
I think people were surprised because everyone thinks that they know what a crab is. Like some of these examples you probably haven't encountered in your life, like echo location, How many people have actually seen a bat in person?
What people would run away from it? And a whale you have to be in the ocean to see it. So it's true that a lot of people haven't, but probably everyone has seen a crab in some way or another, even if it's just dead, even if it's on SpongeBob, right, they think they know what a crab is, and so I think some of it was that people were surprised to find out that not everything I think is a crab is a crap.
The other thing is it went viral during the depths of COVID and people had nothing better to do than be on the internet. So some of it was probably that.
And were you surprised, Oh my god, yes, or like frustrated.
Well, I was surprised because we had recently gotten funded to do research on the evolutionary relationships and morphology of this. But our funding also actually started right before COVID, so it was supposed to be this amazing like tons of international travel blah blah blah. Yeah, we didn't get to do much of that, so you know, we were basically doing like phylogenetic systematics, like obscure stuff that most people don't care about. So I was shocked that it went
like millions of people level viral. But I was kind of annoyed because I think it accidentally set off a few misconceptions. So one of them was that we discovered parsonization and that it was new. I don't want to imply that I just got this, because that's not true. We've known about it since before we knew what DNA even was, like over a century. We've known it's just it hasn't been studied in a really systematic way, so
we're trying to put quantitative tools to the topic. And you know, myself and my collaborators we were like crustacean evolutionary biologists. We were just like, hey, this is cool. But it has taken on a bigger life now. So that's kind of one of the things that I just wanted to set straight. But the other I think more disturbing is the memes kind of set off some misconceptions of that evolution.
And how do you think these misconceptions took root. Do you think it's journalists in good faith misunderstanding or do you think there's an aspect of like, hey, this story would be more exciting if it were a little bit different, so let me make it clickbaity and distort it a little bit. What do you think is going wrong there?
I think a lot of the journalists have been in good faith. A lot of the journalists I talk to have science backgrounds. Yeah, but the headlines are often clicked baby the editors. Yeah, it's more the memes. So the memes, it's like multiple levels of translation. So someone's going to read it and then the next person is going to make a meme of it, and the next person can make a meme with the meal. So I mean that's
like literally what memes are. Right, So when it starts getting to crab the ultimate form, how can that be if it's been lost seven times? Right, it can't. And to say things like any form is firstly invented by nature. Nature doesn't invent anything. Nature doesn't have a brain. That skate's a little too close to intelligence design for me. And then saying that one life form is superior to
another also doesn't really sit well with me. I don't actually think that crabs are better than any other organism except in my heart, which I love them. You know, I got over the incident, so I love them alat now and I got gloves to hold them with, so.
Good move.
So, you know, instead of seeing it as crabs are better than everything else and that's why they evolved, you know, they're part of an ecosystem, part of many eco citizens. We see them all over the world, Like the amount of places that they live is actually quite astonishing. It's you know, from the deepest depths of the ocean and hydrothermal vents where they're like in a chemosynthetic ecosystem and
all the way. There's a crab genus called Himalaya potomon and they're called that because they actually live in the Himalaya Mountains far far away from the ocean. What oh yeah, those guys. They do live near streams, so they get wet at least. But there are some crabs that are so terrestrial that they will drown if you subverse them in the ocean, like, they will live die. Yeah.
Land crabs love it.
Yeah, yeah, So they do have to mate like the larvae go into the water, but that's it other than that land.
So given the crabs are everywhere on Earth a very adaptable to whatever environment, that sets me up perfectly for the question I've been dying to ask you, which is about Zeno krabologists. You know, imagine you're the biologist on some landing party. You're about to, you know, land on some alien planet for the first time. Do you expect to see crabs in some other evolutionary independent environment.
Well, spoiler, but they did make crabs and star Wars recently, so technically I have to say yes.
Right, I'm not a documentary.
No, so I would actually say no realistically, because to be a crab. You have to have the parts of an archipod. To start. You can't have a care pace changing to this shape. If you don't have a care pace, you can't fold up your open if you don't have a segmented body in the first place, the legs and claws, you have to have those. So for me, what I imagine aliens to be, and this, of course now is
just complete speculation based in almost nothing. But you know, I would say, why don't we assume that aliens could be radio organisms? We have those on Earth like starfish. Why wouldn't they be colonial organisms? We have those corals? Right? I think crabs are awesome. And if Disney or any other out you would like to hire me as a consultant to help them make their monsters, I'd be happy. But yeah, I don't actually think that's what you'd see in space.
Well, fascinating space crabs unlikely, that's the new meme.
Yeah, so sad. But you know, if you do somehow get like an arthropod like organism, something that's segmented, then yes, I think it is possible you could. We don't know what the conditions would be like. You know, it's also not star wars where every planet is like one ecosystem. Right, you know, hard to say, right what kind of gravity they have? Do things live in the water at all? Right? Who knows?
Let's end on more exciting notes. So we've poured a little bit of cold water on the you know, nature turns everything into crabs thing. But so let's talk about what is exciting. So you study convergent evolution and crustaceans, what are the interesting scientific questions you're excited about and what are the societal benefits for studying this kind of stuff.
So from the biologist's perspective, we want to know if we can basically predict evolutionary patterns. And I don't necessarily mean predict the future. Although I don't necessarily not mean that, I also mean predict as in, like, do you get why given X, right? And convergent evolution is a really wonderful system for this because we already saw it multiple times. So it's kind of like having experimental rapplicits that have
already happened in nature. So when we do this. I kind of alluded to this when I was talking about animal lizards. They have very similar forms. They're not totally predictable what's going to happen because they have been experimented on. But there is a higher degree of predictability because they are all basically starting from already a very similar point.
So if you look further back to something that evolved a really long time ago convergently, like say eyes vertebrates and several podsic squids, we all have similar eyes, and there are genetic similarities, so like there's a gene called past six that is basically like make eye here when the gene gets expressed, but everything else about the eyes
can be different because they're so distantly related. So I think the fact that within true and false crafts we see this, I mean, it is a distant common ancestor, but it's not so distant. Million years. Yeah, it seems a long time, but like in the scheme of animal diversity, it's not that distant. So seeing also the amount of variation that they have with all the options that their bodies can take, why are we seeing some of the
same basic forms. Are we seeing the same thing being innovated and then just elaborated on, or are we seeing different things happening entirely? Is it adaptive? Is it not adaptive is it a combination? And I think being able to study different scales of convergence is really important because if we just study the same thing, then we're not going to have a fuller picture of whether we can really predict evolutionary outcomes.
And how about we all have to write our NSF grants and other than you know, creating incorrect memes, what are some society reasons to study this?
Well, certainly studying conversion evolution is also important for if I'll use my NSF speak, the bioeconomy. We live in a world where conditions are changing, and we want to have crops that can adapt to changes. We want to develop drugs that are going to be effective against new pathogens, and many of those things, you're going to see that conditions change in the same way multiple times around the world.
We've seen this, of course with variants of COVID having the same mutations, so like when we're trying to make vaccines against them, we're looking at trying to fight convergent evolution, so that can certainly be quite important. Or like you know, we want to see how plants are going to respond to different toxins in the ground. Stuff like this but I think even studying crustaceans is important because, I mean, we've kind of alluded to this, but there's a big
economy in people eating crabs. Like two fisheries in Alaska collapsed about four years ago, both the snow crab, which is a crue crab, and the lasting king crab, which is a false crab, and this is attributed to either climate change and or over fishing. Both are pretty bad, and the reality is it's three hundred and twenty million dollars in the economy, plus people who are not going to be able to eat, plus people's jobs. So that's really serious. And for us to be able to understand
the resilience of these species two changes environmentally. I mean, obviously this's on a smaller scale within a species, but maintaining genetic diversity and stuff like this is really important to know about. Another interesting thing I would say is that there can be some possible knowledge about diseases that we can actually get from crustaceans. For example, crabs can
regenerate their legs if you put them off. Arthur pods have a lot of superpowers because the way that they grow is by molting their entire episoskeleton, and they make what will become a bigger one, but it's like stuck inside and it sucks, and then when the old one fops off, then it kind of inflicts, and so they stick a new leg in there. So you know, obviously, people who have injuries might want to know about ways
that this could be improved. So there's actually quite a lot even in these really obscure animals and seemingly obscure topics. It's true that I'm studying biodiversity. I want to know about why we see the forms that we do, and that may be very high level, but these organisms are important to us.
So you can solve a lot of interesting science mysteries and learn about broader implications. But maybe you can't crack one of the deepest mysteries, which is why husbands are sometimes crabby in the morning.
No, I can't crack that one.
That's more of an NIH question than an NFF question.
That's true, a set is more like our aliens krabby, and that we actually might have some hints about.
Yeah, yeah, NASA does have an extra biology director, or at least we'll see what happens. But they have had but they don't usually do stuff like this. It's more realistic questions that they asked, like how would you detect if there's water on another planet and stuff like that. So yeah, not like literally our organs is going to be crabs on another planet. I think that it's cute, but they're not going to actually give you a million always could.
Do that well. I see lots of great reasons to fund crab research, and Joe, we look forward to seeing what you do in the crabby space in the future.
Thank you so much, thanks for.
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