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S2E09: M Dwarf Planet Biology

This week, we're focusing on the physical biology of creatures living on a planet orbiting an M dwarf star. We talk electric senses, lego crabs, and flying turtle jellyfish!

HOSTED by Dr. Moiya McTier (@GoAstroMo), astrophysicist and folklorist


  1. Robert Ulrich is a PhD candidate at UCLA studying biomineralogy. You can follow Rob and all of the absolutely amazing things they do on twitter at @robertnulrich and online at Oh and be on the lookout for their book, The hard Parts of Life, coming out next year.

  2. Dr. Jimmy Bernot is a marine biologist and postdoc at the National Museum of Natural History. You can follow him on twitter at @JimmyBernot or online at


- Get excited for Mike Schubert's upcoming podcast, The Newest Olympian (@NewestOlympian) coming in September wherever you get your podcasts


Moiya 0:08

Hello there friends. Welcome to Exolore, the show that helps you imagine other worlds with facts and science. I am your host, Dr. Moiya McTier. I'm an astrophysicist who's studied pretty much everything in space from planetary orbits to the radiation leftover from the Big Bang to star formation and black holes and Galaxy evolution. But I am especially interested in the motion of stars and how that affects the habitability of exoplanets, which are planets outside of our solar system. I am also a folklorist who specializes in building and analyzing fictional worlds. And this podcast is my way of sharing those worlds and that knowledge with you. So let's get started.

Moiya 0:53

First thing to do and makes sense to do is to start with introductions, although this is actually the first episode that I'm recording with to return guests, which is very exciting. So hopefully the audience recognizes you, you seem a little bit familiar. But life goes on, things happen, things change. And I feel like both of you have some pretty exciting updates from the last time you were on Exolore. So Jimmy, I'll start with you because you're at the top of my screen. Who are you? What do you do and anything new from the last time you were on the show?

Jimmy 1:24

Hi, everybody. I'm Jimmy Bernot. I'm an invertebrate zoologist. I'm a postdoc now at the Smithsonian Natural History Museum in Washington DC. I study weird little crustaceans, like tiny little planktonic things. I love the like small life that we share this planet with and tend to overlook and yeah, I just started this postdoc position. I graduated in December and I just like did a virtual graduation ceremony. So I guess that's my update.

Moiya 1:49

You wore the robes and everything. Rob, what about you? Who are you? What are you doing and what are all of the absolutely incredible things that you have going on since the last time you were on Exolore?

Rob 2:00

I am a PhD student in geochemistry at UCLA. I consider myself a biomineralogist. I've started to write again, given, I guess, everything and so I'm trying to write a book to hopefully show people how cool biominerals are and how useful environmental research is. And I hope people will appreciate the little things both around us but also inside of us, and I hope we get some more interested in science.

Moiya 2:29

Yes, I absolutely love that. Well, cool. Thank you for for introducing yourselves. I ask all of my guests what fictional worlds they've been inhabiting lately, because this is a podcast about fictional world building. So Rob, are you spending time in any cool fictional worlds?

Rob 2:44

I've been binge watching Seven Deadly Sins. I forget who put me on to it. I feel like I mainly put it on because I saw some of the animations. I was just like, that looks really cool. And so here I am living in the world of I think it's called Britannia.

Moiya 3:00

Interesting, do you have a favorite sin in the show?

Rob 3:03

Yes. The pride sin. He's so handsome.

Moiya 3:09

I do remember watching the show and thinking like most people were pretty hot. But I you know, in real life think most people are pretty hot. So, not much of a deviation. Yeah, Jimmy, any cool fictional worlds that you've been spending time in?

Jimmy 3:23

Yeah, I spent a lot of time reading the last one that came out of the Stormlight archives, which is a Brandon Sanderson epic fantasy series. And actually, it had come out a while ago, but it came out right when I was in the heart of writing up my dissertation. And I was like, if I buy this book, I'll never get my dissertation done. So I didn't buy it. And I totally forgot about it through that whole process. And then one of my close friends was like, "dude, have you finished this book yet?" And I was like, "Oh my gosh, I haven't even started. I forgot that that came out." It's like 500 pages, and I probably read it all in like a few weeks. It was really good.

Moiya 3:59

I really respect your willpower to wait until after the dissertation was done.

Jimmy 4:03

Yeah, well, I love when I'm in like a good fantasy book. That's all I want to do [on] my lunch break. I'm like reading on my Kindle before bed, whatever. So I knew that that would be just like too much of [a] test to like, procrastinate, you know, that was really good. And I'm also watching now Breaking Bad. I had never watched it. So I'm watching that now. But it is really really good. Rob, have you seen it?

Rob 4:27

Yes. I think it was coming out as I was graduating from high school and I think it's one of the reasons why I decided to major in chemistry.

Moiya 4:35


Jimmy 4:36

What's really funny is I watched the first few episodes of it with my dad when it first aired [and] nobody was really watching it yet because my dad is a synthetic organic chemist. And he loved the fact that there was this chemistry element and he knew what was happening when Walt basically makes a red phosphorus bomb in a trailer to get out of a sticky situation and everything like that. I could see what he was doing before he actually did it. But then after like two episodes, there's not really any chemistry anymore. *group laughter*

Moiya 5:09

Was the chemistry at the beginning at least accurate? Like fiction accurate?

Jimmy 5:15

Yeah, I think so

Moiya 5:16

Nice. I did not watch it all the way through. I think I got too turned off by the bathtub, body thing, without going into too many details or getting too gruesome. But yeah, that's what turned me off of the show. But people say got really good. I'll think about putting it back into the rotation maybe?

Jimmy 5:34

Yeah, it is pretty dark, though. So heads up. Yeah.

Moiya 5:37

Thank you for that. All right. Well, those are some cool fictional worlds are the two of you ready to build one of our own?

Jimmy 5:45

Yep, absolutely.

Moiya 5:46

Awesome. So this is the second part in a three part series for one world. And this world is one that is orbiting an M dwarf star. The last episode talked about the environment, the physical setting of this world. And today, Rob and Jimmy are going to help me figure out the biology on this world, which I am so excited about. So just a little recap of the world that we're talking about the physical environment that we decided in the last episode, it is a planet orbiting an M dwarf star. The planet is a little bit more massive and larger than Earth. So we can imagine that there's stronger gravity at the surface of the planet, it's an intermediate distance from its star. So there's probably not much light on the surface, it's probably pretty dim because these M dwarf stars are much cooler and dimmer than our own Sun. We chose an intermediate distance because we know that planets around M dwarf stars typically are going to be much closer to the star. These are smaller systems in general, and closer in planets will be closer to the habitable zone. They might get more heat from the star, but these closest planets are also at risk of being tidally locked. So we wanted to avoid that. So we put it further away. But the planet is over time becoming tidally locked, so days are getting longer.

Jimmy 7:00

Oh, this is so cool. I'm literally taking notes.

Moiya 7:04

Amazing. We really went into detail on this planet. And I hope that in the next episode, I can give just as much detail about the biology. So inside the planet, there are a lot of radioactive materials, especially uranium in the core that generates a lot of heat and that will drive a lot of tectonic and geological activity and volcanism that will add to a thick atmosphere made of sulfur dioxide. There's a lot of water vapor, a lot of ash and particulates from all of the volcanic activity. And that that swirling mess of hot interior stuff in the planet is going to produce strong magnetic fields. So there are going to be beautiful aurora happening at the magnetic poles of this world, which may or may not be the same as the geographic poles on this world, we didn't decide because the the star itself is also giving off a lot of magnetic activity. Cool. So that's the world we're working with. And now it's up to us to imagine what type of life might exist in that world. I want to do something a little bit new In this episode, because I like throwing a bunch of new stuff at the wall at the same time. So typically, in the biology section of the episode, we just focus on one species, but planets have like billions of species on them or at least Earth does. So I'd like to spend a little bit of time brainstorming different species that could potentially exist on this world. Five minutes and we each just throw something out and as many as we come up with in five minutes that's what we do. So five minutes starting now. My first idea is something that's like a worm and yes, Jimmy, this is inspired by the last episode we did together. Worm like creature and I'm imagining it just has like a ring of teeth around the front of it and it digs underground to gather up the uranium which then helps it glow and heat itself on the surface which attracts light or heat seeking pray. Love it. Yeah, that's what I'm imagining. Do any of you have ideas?

Rob 9:00

Yeah, I guess if there's a lot of like sulfide in the air... There's a species of snails that live by hydrothermal vents. And so maybe there would be like something similar to a snail that's making its shell out of like iron sulfide because I'm sure with all the radioactive activity and all the geologic stuff going on, maybe there's a lot of iron around too. And so it's just I don't know, like Magcargo from Pokemon, the lava snail.

Moiya 9:24

Oh, it's like magma, but escargot. Yeah, I see where they were going with that.

Jimmy 9:29

Okay, well, I'm gonna piggyback off of that and say that since there's a snail that has this cool iron shell, I want there to be something that's like an arthropod that's like the most successful life on earth. Something like an insect or a crab with this exoskeleton. And I'm gonna say it can't make its own iron but it hunts the snails and then uses their iron to like build a really strong exoskeleton because it's going to need that since like the gravity is stronger there. You know, it's going to need hard parts. Almost like it's a crab, I guess like a crab type creature. Since we know like on Earth, everything's turning into crabs. Yeah.

Moiya 10:08

That's the end game. I'm imagining something up in the atmosphere because the atmosphere is thicker, maybe it's easier to float up there. And there are also going to be all these harsh particulates from the volcanoes. They're basically just tiny pieces of glass. So I don't know how this would work physically. But I would love there to be something that has like a turtle shell to protect it from the last particulates. But it's also kind of like a hot air balloon in that it just like floats up in the atmosphere.

Jimmy 10:37

Cool. Yeah, it's like a thick atmosphere too. Right? So it'd be like easier to float in it.

Moiya 10:42

Yeah, maybe with with like, a balloon shell type of thing. And these long tendrils coming out from underneath the shell so that it can direct itself in the upper atmosphere.

Jimmy 10:53

Almost like a weird like a turtle jellyfish type thing.

Moiya 10:56

*laughs* Yeah, but up in the air

Rob 11:00

Yeah, and maybe something that like attaches to this flying turtle thing. Or not attaches, but you can just find them on there maybe like some sort of bacteria that's absorbing any of the particulates that are floating around the turtle and just using it to make energy or do whatever they want to do.

Moiya 11:20

Yes, I love it.

Unknown Speaker 11:22

So when you told me the idea of this episode, that was like a thing that I jotted down a few weeks ago, that I think there'd be this big chemosynthetic bacteria thing going on, right? So since there's not much light, what is going to be the primary producers? And I'm thinking on Earth, we have all these chemosynthetic bacteria that are at hydrothermal vents where there's no light, but they absorb sulfur compounds and basically make their energy from that. So I'm thinking that maybe the basic life on this planet, since there's all this sulfur dioxide, is going to be chemosynthetic bacteria. And then the food web's going to build up from that. And there's really cool things that go on then, like there's rings of different sorts of animals near hydrothermal vents. The things that can tolerate the heat the most will be very close to the vent and they'll basically break down the sulfur compounds that have the most energy in the bonds they're breaking. And maybe Rob probably knows more about this than I do. But I know that right around a hydrothermal vent, there's bacteria and animals that break certain bonds, get a lot of energy. And then outside of that there's another ring of things that will use those metabolic end products. They have a little less energy in their sulfur bonds, but they'll break those things down and then further and further out. So we could have like this whole food web here based on bacteria, breaking down these sulfur compounds. And since we're making things up, I love the idea that if there's a ton of uranium, there could be simple plant-like creatures, but instead of having chloroplasts for getting energy from sunlight, what if they're harnessing radioactive energy? So maybe they're taking these uranium compounds, and they're able to harvest their energy from the radioactive decay.

Moiya 13:12

I'm speechless because I love that so much.

Unknown Speaker 13:14

So it's gonna be like a slime mold. It could be like a blob or something. It could look like whatever it wants, but it's gonna have these plastids that use radioactive decay to make its energy. Let's say it's a blob. I like the idea of it being a blob-like thing that can crawl around and harvest.

Moiya 13:31

You're saying hydrothermal vents... Are all of those underwater, or are there some on the surface.

Jimmy 13:36

So all the ones that I'm thinking of are underwater, but I guess you'd get similar things in like Yellowstone. In hot springs, you can get specialized bacteria. So they're all in the water, as far as I know. But in these hot springs, you also get specialized bacteria that can survive otherwise poisonous water because it's either really hot or full of all these acids or toxic chemicals.

Moiya 13:58

Yeah, I'm down with having a species underwater. Or we're focusing more on a species underwater because this planet is around an M dwarf star giving off lots of flares and lots of radiation, and water is a good barrier to protect genetic material from that radiation. Okay, but Rob, what do you think from a biomineralogy standpoint? Is there a place where you think the coolest biominerals form? Is that even a real question?

Rob 14:27

I feel like it would probably happen in some sort of fluid or water. Probably water because the gas is also fluid. So yeah, I think the coolest ones would probably occur in the water just because it'd be easier for whatever life is there to obtain building blocks for whatever it's going to form from either consuming it or from absorbing it from around them, because I feel like that's a lot harder to do when you're just in air. Yeah, yeah. Because like the snails that are terrestrial in real life. They get all of their carbon and stuff from respiration and whatever they're eating. But then when you look at the things that live under water, it's like they're absorbing things into their cells and changing the composition of that water.

Rob 14:31

Oh, hell yeah. So let's go underwater. And that's where the heat is too, closer to the interior of the planet. It's probably going to be pretty cold on the surface, too, since the planet's far from the star.

Jimmy 15:24

Yeah. And I think if there's high concentrations of sulfur everywhere, you could potentially have these bacteria, like the very simplest things forming energy on land or in the water. So I'm imagining that that would be like the basis of both food webs. And then you're going to have things that are grazing on these bacteria that are a bit bigger, and then you could get like, all of the bigger life that's eating those things. So if we want any life on land, or in the water, I think it'd probably be based on eating these bacteria that are doing the main chemosynthetic activity.

Moiya 15:58

Yes. Awesome. Okay, do you feel any sort of particular affinity towards any of the species we thought of earlier? Or do we want to imagine a new one for this underwater environment?

Rob 16:10

Well, I feel like if we have like these crustaceans, snails, I feel like they could be amphibious. Who knows? Yeah.

Moiya 16:17

Okay. So things that are sometimes underwater and sometimes on the land. You two are closer to biologists than I am, what do you think is important to know about this species? Or to build about this species?

Jimmy 16:34

Well, I guess from the most basic thing, it's going to be like, what is it eating and does anything eat it? Kind of like predator-prey type interaction so we can get a feel for what this creature is doing.

Moiya 16:45


Jimmy 16:46

So are we going to focus on the crab we think? I feel like if it's gonna have this hard armor that can help it structurally survive this heavy gravity, especially if it's going to come out on land. But also maybe it has to have this thick armor because there's some predator that's going to be eating this thing. And I'm thinking maybe if it has this hard armor, its predator could be almost like a mosquito type creature, right? Like something that's going to have like a long sucking mouth part like a proboscis or something. And that's going to look for a little gap in the armor and feed on it that way. So maybe it doesn't have to be giant, it doesn't have to be consuming the whole crab, but there could be otherworldly mosquitoes on this planet that are going to try to eat the crabs. And the crabs are going to have to watch out for those things, maybe defend themselves in some way.

Moiya 17:41

I love the idea of a predator that works as a collective.

Jimmy 17:45

Yeah, so it could be like swarms. Maybe, you know, they travel in a swarm looking for these crabs. Yeah

Rob 17:51

That's terrifying.

Moiya 17:55

It is terrifying. I definitely don't want to be one of these crabs.

Rob 17:58

Yeah, initially, I was just thinking, is our little flying turtle thing gonna be intimidating enough to be the predator?

Jimmy 18:06

Well, they could eat the mosquitoes. It has these tentacles and everything. So that can be hard in this circle of life.

Moiya 18:13

Yeah, just because the turtles prey on the mosquitoes that prey on the crab doesn't necessarily mean that the turtle preys on the crab.

Jimmy 18:21

Exactly. Yeah, because especially if we're imagining these little mosquito type things are much smaller than the crabs, but they're gonna travel in a swarm. So if like 100 of them or 1000 of them get on the crab, maybe they're gonna suck all the fluids out of it and kill it

Moiya 18:36

Suck all the fluid.

Jimmy 18:39

I'm a parasitologist, so you're going to get weird stuff with me. Yeah, so I think that's kind of a cool idea to have these predators that are smaller than the prey.

Moiya 18:51

Rob, do you have any immediate reactions to this?

Rob 18:54

No, I just really like the idea of the turtle tentacles sucking up some of the mosquitoes that get up there.

Moiya 19:02

Yeah, I'm picturing them as tongues, but also hands that can just scoop in the mosquitoes as they fly through.

Jimmy 19:10

Yeah, so maybe the crabs don't have a huge defense against these mosquitoes. Maybe they're running away, trying to hide from them. Potentially they could go to the water maybe to try to get away from the mosquitoes. But maybe if they're on land, they tried to do something to signal the flying turtle jellyfish type thing to come and attack the swarms. They could have a sound that they make or something to signal that these mosquitoes are attacking them. And maybe that is then a signal to these turtle jellyfish type creatures to come in and feed on the mosquitoes.

Moiya 19:47

Yeah, like if there... I don't want to just... you know what, I do want to just make stuff up. That is the point of this show. Maybe if the crabs, like you said, can make a noise... What noise would attract a creature? A noise that makes them think they might mate soon? A noise that makes them think there's food there? There is food there. How are the crabs tricking the turtles into coming to eat the mosquitoes?

Jimmy 20:11

Well, I was thinking it could just not be a trick so much as literally like a signal to call. Almost like they're working cooperatively. And so I'm thinking like plants. Sometimes when they're being eaten by caterpillars, they release like specific compounds that go into the air. And if a wasp that eats these caterpillars detects that compound, they're like, "Oh, a caterpillar must be eating this plant" and they'll go to the plants to eat the caterpillars. So you have like organisms that signal other organisms basically being like, I'm being eaten, and then like a predator of that creature that's eating it will come in. It could also just be that when the crabs are being eaten, the scent of their blood or whatever attracts the tenticle turtle creature

Moiya 21:00

Bloodthirsty turtle jellyfish, yep

Jimmy 21:04

But it just is like, "oh, there's a crab bleeding nearby, there must be these mosquito things nearby. I'm going to go in there to eat the mosquitoes."

Moiya 21:12

Now, I'm thinking that in the future, if there's ever a crab war, all of these turtle jellyfish are gonna come, even though there's no mosquitoes. Although maybe the mosquitoes would also just come because of the blood.

Jimmy 21:28

Yeah, if the flying things are eating the mosquitoes. I mean, it doesn't have to be like they're always doing that for the benefit of the crab. One of these crabs could die and all the mosquitoes are there. And these turtle jellyfish creatures are still going to be attracted to that, because they're going there to eat the mosquitoes, not because they care about the crabs.

Moiya 21:45

Yes, I have to remember, the nature doesn't care. It's just doing whatever I can to protect itself.

Jimmy 21:50

Yeah, I mean, in this case, it would be like a vulture, you know. It's going there to clean up or eat some scraps.

Moiya 21:57

I'd love to think more about the crab and what it looks like and what its features are. And it sounds like the shell is going to be really important. And we have here an expert on shells being made. So Rob, I know that you've recently published a paper about how the biology and the environment of a creature both affect the types of biominerals that it can make in different ways. So do you have any thoughts or musings on what might get into this crab shell and how that might happen in this amphibious environment?

Rob 22:32

Yeah, totally. I feel like if they are eating our little lava snail things to get iron and the atmosphere is full of sulfides, then I feel like the mineral could be an iron sulfide. I forget what minerals are made out of iron sulfide. Or just like some sort of iron mineral,

Jimmy 22:51

I'm wondering what color is it going to be? I'm thinking like iron... is it going to be rust colored, like a red type thing? Or if there's sulfur mixed in it, does that make it a totally different color? It could maybe even depend on its diet at the time. It could change colors or be different colors depending on what it's eating or what chemicals it's absorbing more of.

Moiya 23:14

Yes, I love when the individuals within the species look different from each other. That's polymorphism?

Jimmy 23:23


Moiya 23:23

Fuck yeah! But I also really love when an individual in a species looks different over its lifetime. I just think that that that's like a really nice poetic metaphor for like growth or something. I don't know. I like it.

Rob 23:38

Okay, so one of the iron sulphide minerals is pyrite. I forgot it was an iron sulphide. For some reason, I thought it was the lead. It's also it's what makes up fool's gold.

Jimmy 23:48

I love that. So it's gonna be like this glittering gold crab thing. I love that. It grows like cubes, doesn't it? Yeah, so it's gonna have this awesome shell. Okay, yeah. Tell us more about that, Rob.

Rob 24:02

Yeah, so I guess it's eating our snails to get the iron, but then it's also breathing in sulfur and then doing whatever respiration will be like on this point. And because it's a crab, it'll probably be molting. It'll probably have its ooze, where the mineralization is going to take place.

Moiya 24:26

What do you mean ooze? When you say ooze, I'm picturing just goo leaking out of this crab's body. Is that what you mean?

Rob 24:36

So when, at least for lobsters... I don't know about the crabs specifically. But when they molt, they partially dissolve the undermost part of the shell and it starts to separate. And then they are starting to mineralize the new shell as well as simultaneously recycle parts of the old shell.

Jimmy 24:59

You got the biology better than I do and I study crustaceans. *laughter* Because their shell can't grow from the inside out, they can't keep making their body bigger from the inside. Because the exoskeleton is hard and constraining them, they have to absorb some of the minerals from the outside of their body, and they're growing a new body inside that is bigger than the old one. But for it to be bigger than the old one and be fitting inside the old one, it's kind of soft, right? And then it'll break out of its shell, and then expand and harden.

Moiya 25:34

I have a simple question. What do crabs look like naked?

Jimmy 25:39

So they still have the shell. As soon as they come out, they have a thin exoskeleton so they look like a crab still, but they are very weak. Their legs don't work well because, you know, we have a skeleton inside of our body that our muscles attach to, but their muscles attach to the skeleton that's outside of their body. So if that's not hard, their muscles don't have very good hard parts to move on. So they're very weak at this stage. They don't crawl very well. And that is when predators like to eat them the most because they're relatively unprotected. And if anybody's had soft shell crab, what you're eating is these crabs that have molted recently and don't have hard mineralized exoskeletons yet.

Moiya 26:27

The next time I go to a restaurant and order softshell crab, which has never happened... So the first time I do that, I will be referring to it as a naked crab. That is what I'll order.

Jimmy 26:38

I'm thinking of Futurama. I don't know if you've seen that episode when Zoidberg molts. But he is soft and... *laughter*

Moiya 26:47

Yes, yes. Speaking of fictional characters inspired by crabs, is there anything else we want to add to this? Because it you know, it's an alien planet. It doesn't have to be a crab, but it can be inspired by a crab. So what what other features? In your heart of hearts, what do you want this crab to be?

Jimmy 27:05

Yeah, well, I'm thinking it's gonna have to have pretty stout legs to walk around on on land in this higher gravity. It could have any number of legs. I would imagine it has to have like more than four, right? Because if it's kind of moving around like that, and it probably needs more than four to support itself. Six, 8, 10, 12. Like we could have whatever we wanted to have. I think it might have claws of some sort. Maybe instead of having a big set of two claws, it has like multiple sets of small claws, say four or six. And it's going to use those to try to like defend itself from the mosquitoes, right? So instead of having big claws, like a crab or lobster, it could have multiple sets of small ones that it can... I'm gesturing now. Nobody can see it.

Moiya 27:50

It's okay, we know what's happening

Jimmy 27:52 like, snap at these little incoming mosquito-like predators that are going to feed on it.

Moiya 27:58

Yeah. And all around too. Not just in the front.

Jimmy 28:00

Exactly, yeah. Not just in the front. All around right.

Rob 28:04

I was also was thinking, maybe it could be like an isopod, like the rolly pollies. It's protected then. Yeah, because it's pyrite. Maybe instead of it being like a roll, it just turns into like a cube.

Jimmy 28:19

Yeah, I love that. I love the idea that it would fold into this geometric shape. I think that's so cool.

Moiya 28:27

Yeah, that's sick. That's a good note to take a break on. And then when we come back, we'll talk about more of the physical characteristics of this hypercube crab thing.

Moiya 28:40

Okay, I am recording this ad on vacation without my microphone, so I apologize for the terrible audio quality. But to make up for it, here's a fun little piece of information, a fun little Moiya nugget. When I was in seventh grade, my social studies teacher decided to teach a lesson on Greek mythology, which was awesome. But I, being the overachiever that I am, obviously supplemented that material by reading Rick Riordan's Percy Jackson series, Percy Jackson and the Olympians. And there was a boy in the class who was reading the series at the same time. His name was Dayton, and he was so cute. And we started dating because he was my first boyfriend. So Dayton, wherever you are, I hope you're living a good life. But you, listener, since I know Dayton's probably not listening, I want you to get excited about this series because Mike Schubert of the Multitude collective is coming out with a new podcast about this Percy Jackson and the Olympians series. It's called the Newest Olympian. Mike's going to be reading this series for the very first time as an adult man, and I am just so excited to experience it for the first time again, through his eyes and his voice. And I hope that you get excited about it too. So the Newest Olympian is coming out in September. I hope you check it out. I will be on one of the episodes, though I don't know which one. Mike told me that I should read chapter seven. I'm just gonna read the whole book because if I recall correctly, it was just a gosh darn delight. So yeah, check out the Newest Olympian. It's the upcoming podcast from Mike Schubert. And also check out the other Multitude shows. There's Spirits, Join The Party, Horse, all of them are great. Yeah, let's get back to the show.

Moiya 30:22

All right, welcome back from the break. What else do we want to have on this crab? We also haven't really explored what this crab is doing underwater. So maybe let's think about its underwater life a little bit more. What types of creatures or species will it be interacting with down in the in the deep red sea? Because it's an M dwarf world. So you know, the star is red?

Jimmy 30:49

Well, I'm thinking most crabs on Earth, it has to go back to the sea to lay its eggs. Because I'm imagining its babies might not be able to survive the radioactivity of the land. So it's going to go back to the more protected aquatic environment to lay eggs. And then things are going to hatch out of the eggs that are probably a small, little larval stage. So that could be something that swims around in the water. You know, it could be a totally different shape. It could be whatever we want, and it's going to live its life initially as this aquatic thing before it molts into a crab that can then go on land or be in the water.

Moiya 31:29

Does anything eat these eggs?

Rob 31:31

There has to be.

Jimmy 31:35

You know, that's before it's built a strong skeleton or whatever. So what else do we have on here?

Moiya 31:41

We don't have much in the ocean of this world. So what type of thing do we imagine is going to eat these eggs? What's living in the water?

Rob 31:49

My head goes straight to that barracuda in Finding Nemo.

Jimmy 31:53

Okay, totally. I was imagining some sort of fish like thing, right. We could have this really fast-swimming torpedo-shaped fish. You know, there's this extinct group of fish called ostracoderms and placoderms. You can see them at natural history museums because they were fish, but they had armor outside of their body too. So again, maybe because this is a really tough environment, it could be a fish, but it could have shell type plates on the outside of its body to protect it.

Moiya 32:32

But would they be in the shallow parts of the ocean? Because how deep is the crab going to lay its eggs? I imagine it stays pretty close to the shore.

Jimmy 32:41

I think so too. But then I'm thinking the larvae that hatch are out swimming in the ocean. Because usually that happens with creatures that like go back to the sea to lay their eggs. Their babies will hatch and then go out swimming around in the ocean eating other things. So maybe these little larvae swim deep down and they graze on the bacterial mats of these synthetic bacteria. And that's when they could be eaten by either this armored barracuda type thing. Potentially, if they're slow and grazing on the bacteria, the snails could even eat the babies

Rob 33:19

Fight back!

Jimmy 33:24

As adults, the crabs could be eating the snails but that doesn't mean that when they're babies and they're really tiny, the snails could be even predating them.

Rob 33:35

Since we're becoming tidally locked, what is the ocean like? Like, is there waves? Are there currents?

Moiya 33:44

That's a great question, Rob. I imagine that the tides are probably not unpredictable. Like they're still going to happen around the same time every day, but it is getting like either earlier or later, depending on like where you are on the world and which tide it is.

Jimmy 34:01

Is the sun big? Like, is this bigger than our sun?

Moiya 34:04

It's small, it's much smaller, like 10% the size of our sun.

Jimmy 34:09

But it's close to it.

Moiya 34:10

So the planet is technically closer to its star than we are to our Sun. But because the sun is cooler and smaller, it's getting less energy. So imagine that this planet is getting the same amount of light and heat as maybe something in the asteroid belt between Mars and Jupiter.

Jimmy 34:29

Okay, I'm just thinking if it's close to this sun, and it sounds like gravity's having a pretty big effect on it because it's getting tidally locked, the tides would potentially be very dramatic. Because as this planet is spinning slowly, the part of the planet that is facing the sun, like the sun is going to have a big gravitational effect and be pulling the water to it. So instead of the tide being caused by like the moon like it is on Earth, you might have the tide coming by the sun, you know? Just as the planet is spinning, the water is going to be not spinning as much, right? Because it's almost like the water is kind of tidally locked and the planet is like spinning beneath it, you could have really crazy tides. Then there could be no surface of land, for instance, that doesn't have water on it at some time. And I think that would be a really cool idea, right? So if the tide is so dramatic, then at low tide, the land is exposed, and at high tide, the water is completely covering that part of the land.

Moiya 35:36

I don't think that the tides will be quite that extreme because the the tides on Earth are caused by both the moon and the sun. And this planet can have a moon too. But I don't think that it would be like every day, it gets covered and then uncovered, I think it would probably be something where over the span of 100 or whatever years, maybe the surface of the planet changes very rapidly. Okay, but I think one thing that will be interesting on the day timescale will be the the warm part on the planet. Because the the planet's going to be rotating more slowly, the star will spend more time over each part of the planet, if that makes sense. So I imagine there might be creatures that follow the sunspot as the planet rotates.

Jimmy 36:24

Okay, what do we think the length of a day is on this planet? Like at least to start? Is it 10 days? Or is it 100 years? Like, I'm wondering how slow this thing is spinning, you know?

Moiya 36:37

Well, it's a smaller system. So the let's say that a year on this planet is probably... let's say six months, make it easy. And let's say that a day is like a month.

Jimmy 36:49

Okay. Okay, that's interesting. Yeah. So you're in the light for like, a pretty long time. And then in the dark, also, for a long time. Yeah. So creatures could probably follow the light, right? Because if it's spinning that slowly, you can just kind of track that light by migrating with it. Okay, that's cool. Yeah, yeah,

Rob 37:10

I'm also thinking about -- this is like, definitely not my field at all -- the physics of the magnetic field coming from our star interacting with the one coming from our planet, and how the area of where that interaction is happening, also changes with the rotating thing. And then all of our things are made out of iron. They're probably interacting with the magnetic field too.

Moiya 37:35

I'm wondering if that would help them with navigation so that they can very easily follow the sun. It's like they can follow either the heat or the the magnetic pull.

Jimmy 37:45

They can feel the pull of it. Yeah. That's so cool. They're magnetic animals. I think birds have that, right? I think they have small molecules in their brain or something that let them sense the magnetic field of the earth so they know where north is. And that helps them navigate. So these things, if they have [iron] covering their bodies, they're going to have a very strong sense of where the poles are. Yeah, that's cool.

Moiya 38:11

So cool. I think dogs can do that, too.

Rob 38:15

Yeah. And then maybe they don't have eyes because if it's dark most of the time anyway, they just feel disturbance or disturbance in the Force.

Moiya 38:27

Even if they're in the water, they can feel the waves. And the air might be thick enough that especially the turtle jellyfish can do it, but maybe even creatures on the surface on the land have these long antennae that can feel changes in the wind or something.

Jimmy 38:44

Yeah, totally. I mean, there's definitely sea creatures that do that, that have very long antennae that can sense water movement, either to find their prey or to know to move away. So the jellyfish thing is gonna have that for sure. Right? Because it's going to have super long string-like feelers to sense if these mosquito creatures are moving around, disturbing the air currents. It kind of makes sense for them not to have eyes if it is this very like toxic environment. I feel like eyes are normally these soft things with lenses that are very like subject to damage. So that could be a really cool element that nothing has eyes or at least not eyes as we know them.

Rob 39:26

Not even with water or air currents. I was thinking just the magnetic field...

Jimmy 39:30

...can feel the magnet of the crab

Rob 39:33

Yeah. Is it sharks, right, that can do the electricity thing?

Jimmy 39:41

Yeah, they have these little ampullae of Lorenzini. These little things that let them sense electric fields. Electric eels and stuff also have that, so yeah, the mosquitoes could have that. So they're sensing the magnetic field that each little iron crab is making. That would be a really cool way for them to hunt. And it also means that the crab might not have much of a way to hide. And that's why it needs all these defenses like being able to turn into a cube and yeah, that's really cool. That's really cool.

Moiya 40:10

Yeah, I love that a lot. Maybe it's time to bring in more of the symbiotic relationship and what that would look like.

Rob 40:18

I think we touched on it, at least like the bacteria on the turtle jellyfish thingy.

Jimmy 40:23

Yes. So for one thing, I'll just say symbiotic in the original sense of the word just means living together. A parasite is technically a symbiont. Now in popular terms, people tend to think of symbiosis as being mutualist, where both things benefit. But you could have symbioses that are like a barnacle on a whale. The whale's not really getting a benefit, but the barnacle does, then they're technically living together. Yeah, but I'm thinking there could be certain types of bacteria or other creatures that like to live on the exoskeleton of the crabs and they could have some benefits. They get carried around by the crabs, but maybe the crabs also feed on them. So I'm thinking of how there's actually ants on earth that are like farmers. They have herds of aphids that they protect and the aphids produce sugar water, basically, that the ants eat. So I'm thinking these crabs could have something maybe living on their surface that gets shelter but produces something that the crabs eat, because then when they're folded up, they're feeding on these things that are living on the surface of the other crabs they're folded around.

Moiya 41:41


Jimmy 41:42

I'm not sure what that creature is. It could just be bacteria. It could be smaller little insect-like things or something. It could be anything.

Rob 41:51

Yeah, I guess we could also potentially do something with the plants. I watched a documentary pretty recently about the fig tree and the fig tree wasp and the mutualism, I was just like, "Ahh, that's so cool!"

Moiya 42:05

What do they do? What does the wasp do to the plant and vice versa?

Rob 42:08

It's like these wasps plant eggs inside of the figs. And then the figs fall and then the eggs hatch. And the wasps do the pollinating. I don't know, it's like the queen of trees or something.

Jimmy 42:24

Yeah, so these fig wasps like pollinate figs in the wild. Their babies also hatch out from inside the figs. Their babies live inside of them and feed on the figs, I think, and then come out. So that is like they're both getting a benefit. And then what's crazy is there's multiple levels. So then there's other wasps that eat the fig wasp babies that are inside the figs. And then there's even a third level of wasps that eat the wasps that are eating the fig wasps.

Moiya 42:54

It's wasp-ception.

Jimmy 42:55

Yeah, it's like this fig is like a whole world.

Moiya 42:58

Why is nature's so cool? I love it.

Jimmy 43:02

If these are big crabs that have all these complex, pyrite shapes on them, you could have multiple levels of things happening on them. So just imagine small plant-like things that are growing. And then there's insect-like things eating those plant-like things. And the crabs, if they fold into their geometric shape, can feed on those things to sustain themselves in their defensive position.

Rob 43:26

Maybe our crabs are pulling up our radioactive-consuming plants and sticking them on themselves to signal to the big turtle jellyfish things, "Here I am! There might be food here."

Moiya 43:40

"Here I am, come eat my mosquitoes!"

Jimmy 43:42

I love that. You just made up something that actually exists. There are crabs that do that. They pick up sea anemonies and stuff. And they will put them onto themselves so that now there's a singing thing living on it that'll protect itself from other predators. So the crabs could be harvesting things on this planet and sticking them onto themselves to like create this ecosystem on their shells.

Moiya 44:08

Part of me wishes this wasn't an audio medium, because listeners if you could just see the faces that all of us have made at one point or another in this episode. Like I'm pretty sure each of us has had our mind blown at one moment or another. We are close to the top of the hour. So I'm wondering if you have any other burning ideas about these crab people that you want to throw out at the end?

Jimmy 44:33

I kind of like the idea that they might also move in groups. I think it's cool to think about them as not just being like these totally solitary animals, but traveling in groups that might help them also defend themselves from predators. So kinda like how a meerkat will be like, "oh, a predator is coming" and will call or something to alert the other meerkats [to] get underground. There's a hawk coming. The crabs could do that. If they sense the mosquito type creatures coming somehow, they could signal all the other ones to curl up into their shell formation to protect themselves. I think that's cool. That would be cool.

Moiya 45:11

I like that a lot.

Rob 45:12

Oh, and they can stack on top of each other, like around the younger ones.

Jimmy 45:16

Yeah, yeah like a herd of buffalo or something.

Moiya 45:19

Or like little Lego fortresses around all of the younger ones.

Jimmy 45:25

Yeah, cuz they're different shapes. Oh that is so cool that like the small ones could interlock into the geometric shapes of the big ones Oh, so what if that's their main defense, that they come together and form a giant geometric shape? It could be that if these mosquito things come by, they can crawl into the shape and just stay like that for days. And so then the mosquitoes have to be constantly on the move, because if [the crabs] get into their geometric formation, they're gonna stay like that until the mosquitoes leave. So the mosquitoes' game is having to find crabs before they get into their defensive position.

Moiya 46:06

Yes, I love the idea of them moving in groups because that sets up the possibility for later on in the culture episode, we're going to be imagining them as their more evolved, very sentient form. And if they already are moving in groups, then maybe their brains will develop to think of social contacts and group dynamics in a similar way to us. So that'll be interesting.

Jimmy 46:30

So I'm gonna plant a seed for this episode. Now that I'm thinking about it, there's no reason that these things can't keep growing forever. So lobsters don't have an end size, they can just keep molting over their life. And the longer they live, the bigger they get. So in this crab society, you could have elders that are giant. Like they could be a city or something. I mean, you could decide how fast you want these things to grow. But you could have these elder crabs that have been living for hundreds or 1000s of years. And as a result, they could be 100 times or 1000 times bigger than the young ones.

Moiya 47:12

That make sense, too, if they have a slow metabolism. I've seen things that connect a slow metabolism to longer lifespan.

Jimmy 47:20

Yeah. And again, like the crustaceans, they can keep molting, they can keep growing.

Moiya 47:25

Yeah, as long as there's material around and this planet does have plenty of material. Yeah. Rob, do you have any predictions or requests for the culture episode?

Rob 47:35

Well, I liked how we talked about art during the watermelon snow one. I'd be very interested about, like, the art theme in this world.

Moiya 47:43

Yes, we'll be sure to talk about it. So we are at the top of the hour. Unfortunately, we have to wrap up. But when our listeners want to learn more about you and follow the amazing stuff you do, where can they find that? Rob? Where can people find you on the interwebs?

Rob 47:59

I'm And then all of my social media handles are the same: @robertnulrich

Moiya 48:08

Dope. And the links to your website and to your Twitter will be in the show notes. What else are you working on? I know you have stuff going on.

Rob 48:17

Oh, I'm just publishing a lot of papers, at least trying to.

Moiya 48:20


Rob 48:21

*laughs* No big deal. Trying to write this book. I'm like, I don't know. I have a lot of things on the fire. Oh, I got to the next part of the nomination process to do a TED Ed lesson on biominerals, which is really exciting. I'm so excited.

Moiya 48:33

That's really great. Congrats!

Rob 48:39

Yeah, it's been fun sharing more achievements on social media, because then it's more fun and more people celebrate with you instead of it just being an email.

Moiya 48:50

Especially these days when it's really difficult to celebrate big wins in quarantine. So I'm glad you have the Twitters. Jimmy, what about you? Where can people find you on the internet?

Jimmy 49:04

Yeah, pretty easy. I'm @JimmyBernot pretty much everywhere. So on Instagram, Twitter, I'm even on tik tok. Now I'm just dipping my toes into the water on tik tok, and my website's so you could keep up to date with the things that I'm doing there. And I have links to my social media accounts and stuff. I, like Rob, am trying to publish a bunch of stuff. So I'm trying to publish my remaining dissertation chapters that I haven't published yet. I'm working on two genomes of barnacles and a review paper that's reviewing: how many times have copepods (the thing that I specialize on) evolved to be parasitic? I've been thinking about these symbioses a lot recently, because some of them have evolved to be parasitic like hundreds of millions of years ago, and have now this giant diversity of all sorts of parasites. And other ones are probably currently at the stage where they're evolving to be parasitic, and they literally live on the gills of crabs or in the shell of a hermit crab. And it's not clear if they're a parasite if they're just hanging out there, but probably if we could come back in ~50 million years, they might be parasites then. Yeah, so it's pretty cool and these copepods, I think are the most interesting thing. So that's why I hope to spend my career learning more about them.

Moiya 50:24

Yeah, that's incredible. Good luck with your postdoc. Good luck with the move. I wish you both many, many publications. It feels good to be out of science. I don't have to think about that currency. But I hope that the two of you are just rolling in the publication dough. Cash in those publications. Yes. All right. Well, thank you so much for joining me and imagining these really cool pyrite cubic geometric crabs on this m dwarf world.

Jimmy 50:57

Thanks, Moiya. This has been so much fun.

Moiya 51:03

Thank you so much to Rob Ulrich and Dr. Jimmy Bernot for helping me imagine the life on this M dwarf world, the second part in a three part series. Here are a few of the facts that we used to build this world. One, there are ants that actually farm aphids as if they're cattle, which is super dope and hopefully not as ethically dubious as it is when humans do it. Second, there are plants that can send out chemical messages to parasitic wasps to warn them when they're being eaten. And these messages that are sent over chemicals called volatiles, they can actually be precise enough to identify the type of animal like a caterpillar that is eating them so that the wasps know if they can also eat this creature. Third, sharks have the ability to sense magnetic fields. And they do this through electro receptor cells around their snout and their gills called Ampullae of Lorenzini. It's really cool. And we used that to figure out how you could actually sense things along magnetic field lines in this world. We used all of these facts to build out a race of amphibious kind of crab-like creatures that have pyrite in their shells and can fold themselves into geometric configurations like tetrahedrons or hyper cubes. They get the pyrite in their shells by two means: they eat snails that have iron in their shells, and they get sulfides from the air. So iron plus sulfides, iron sulfide, or pyrite, which is one of these iron sulfides. These crabs move in groups and when they detect a predator nearby, they can interlock their bodies in really cool ways to form these these domes almost or these these structures that can protect their young, their vulnerable young. And they can basically live forever as long as they have enough material to be able to molt their old shells and get new ones. They'll just continue growing and growing until they're giant old crabs that are wise and can lead their societies. In the next episode, we're going to be imagining the culture of this crab species and I am so excited. I hope you come back to join me in the third and final part of this world. I would also really love to see any art you make inspired by these pyrite shelled crabs. Please share any drawings or songs or stories that you write with Exolorepod. You can tag us on Twitter or Instagram at @ExolorePod, or you can send it to I have a fan art page on the website and I would love to be able to add your work. Also, these pyrite crabs remind me of the pyrite turtles in the very first episode of Exolore. It has some audio issues, but the content is great and I have three amazing guests on the episode. Check out episode one, the very first episode of Exolore, if you want to hear about some other fun pyrite shelled creatures.

Moiya 54:08

This episode of Exolore was edited by Mischa Stanton. The cover art is by Stephen J. Reisig. The transcript is by Iesir Moss, and the music is from purple Exolore is a member of Multitude Productions, an independent podcast collective and production studio. I highly recommend checking out the other Multitude shows. All you have to do is type "multitude" into the search bar of your favorite podcast app. If you want to support me and my worldbuilding work, the first way to do that is to rate and review the show on Apple podcasts. It's free, you don't need any sort of Apple device and it really does make a difference and help the show grow. Second, you can support me on Patreon. Your monthly support would make it possible for me to continue working on this passion project of mine. So if you're able, please head on over to if you can. Be sure to follow Exolore on Twitter or Instagram at @Exolorepod. And if you like this episode, share it with your friends and subscribe to the show because that way you can catch me next time on another world.

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