Selects: How Coelacanths Work

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1:01John Polk story on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hi, everyone. Happy weekend. I hope you're having a lovely, lovely Saturday wherever you are in the world. We're going to jump back in time to June 6, 2017 to talk about coelacanths, how coelacanths work. What in the world is a coelacanth? I think I kind of remember. Check it out right now.

1:34Welcome to Stuff You Should Know, a production of iHeartRadio.

1:45Hey, and welcome to the podcast. I'm Josh Clark with Charles W. Chuck Bright, Jerry Jerome Rowland, and just the whole HowStuffWorks gang, here to present to you Stuff You Should Know. All three of us. How you doing? I'm good. Yeah? Yeah. I'm a little caffeinated, I should warn you. Oh. A little bit, like when teeth are about to just come right out of my face. That's not good. You know, we did a video about coelacanths one time. Yeah, like, was it This Day in History about when they were discovered? Yeah. I ran across it. Because SMACT is familiar to me, and the constant fear we have of recording an entire podcast over is sort of always there.

2:29Yeah, the fear that sometimes comes true. Yeah. So I definitely went back and looked, and I was like, I knew he did something. Yeah, we were trapped in a shipping container, right? I didn't watch it. I didn't either. I just saw enough to say, oh, yeah, I remember that one. Yeah. That really weird, weird thing we did. But this is really cool, I think. I do, too. The two coelacanths were, well, they're interesting. Despite what the HowStuffWorks article would lead you to believe. It was, yeah, it was a little thin, wasn't it? A little bit. It was all right. Okay. But luckily the rest of the internet is there for us.

3:06Right. Thanks especially to Smithsonian and Mental Floss for this one, right? Yeah. That Mental Floss article was kind of neat, actually. It was. So you want to go back to the beginning? actually the second beginning maybe. Oh, well, I don't know what you're talking about now, so just go ahead. Okay, well, follow me. We'll go back to the very beginning. We'll go back to something about 400 million years ago. Okay. During the Devonian period, which is a.k.a. the rise of the fish. Yes. The age of the fish, right? And in this Devonian period, there's a lot, a lot of stuff going on. Things have been swimming around for a while.

3:48On Earth, there's a nice atmosphere that's developed. The things in the ocean are starting to say, oh, what's out there? I want to see what's on land. Yeah, maybe I can just crawl out and see. Yeah, I want to taste clover. So they start trying. And during this period, there was the progression from the sea to the land. Yeah. And one of those things that was starting to develop legs to get onto land was called the coelacanth. Yeah, which A, it means hollow spine, which we'll get to. There's a reason for that. Right. And B, it's spelled C-O-E-L-A-C-A-N-T-H, which is, you know, not how you would think it might be spelled.

4:36No. Or pronounced, rather. Right. Either one. But it's coelacanth. It is coelacanth. And what it is is a fish that is, like you said, been around for a long, long time. It's kind of funny looking. And we'll get into all the physical characteristics that make it unusual in a sec. But it is notable mainly for the fact that everyone thought it was gone forever. Right. Until it was suddenly discovered, this thing that swam with the dinosaurs was discovered anew in the 1930s. Right. And then again a little bit later on. Yeah, because it pops up for the first time around 407 million years ago, I think I said.

5:22And then it just drops off 80 million years ago. So they said, well, a lot of stuff went the way of the dinosaur around the time the dinosaurs went away. So that's probably what happened to the coelacanth. So it was quite a big surprise in the 1930s when a trawler that was out fishing, a trawler called the Nareen, which is captained by Hendrick Goosen off the coast of South Africa, came in, and as was Captain Goosen's want, he contacted the director of the local museum in East London, a woman named Miss Marjorie Courtney Latimer. and she used to come over and look at the fish loads this guy would bring in because they were buddies.

6:07Yeah. And he gave her a call like normal and said, I got a load. You want to come look at it? And she was like, it's two days before Christmas and it's blazing hot out. Don't forget we're in South Africa at the time. And she's like, I don't feel like it. But the world was saved. The world of ichthyology was saved this day. Yeah. Because this lady, Marjorie Courtney Latimer, was so nice that she decided to go look at the fish anyway just to wish the captain and his crew a Merry Christmas. So she takes a look at this fish, and here is her quote, as she recounted. It wasn't her quote at the time.

6:47Her quote at the time is probably a South African expletive. But she said later, I picked away the layers of slime to reveal the most beautiful fish I had ever seen. And, of course, only a fish lover can find this thing truly beautiful. Yeah. Because it's kind of ugly. It is. It was five feet long, a pale mauvey blue with faint flecks of whiter spots. It had an iridescent silver-blue-green sheen all over. It was covered in hard scales, and it had four limb-like fins and a strange little puppy dog tail. Not literally, of course. It was said, which would be great, though, actually. Yeah. I did. That's the dogfish that has that.

7:29It was such a beautiful fish, more like a big china ornament, but I didn't know what it was. And it was pretty faithful that she was called in to look at this thing because it ended up being one of the most important zoological finds of history, probably. Of the 20th century, at least. Yeah. For sure. Yeah, this woman's curiosity, something in her said, This is weird. This is unusual. This is something worth looking into. So she took it with her. This thing was like five feet long, just under two meters, about 100 and how many pounds? 127 pounds. This is a significant fish. Yeah. And Ms. Courtney Latimer talked her way into a cab with it.

8:14She took a cab back to the East London Museum with this fish stuffed in the back seat. And she took it to the taxidermist and had it stuffed. Unfortunately, the taxidermist wasn't completely aware of how to preserve a fish for identification. And threw out the skeleton and the gills, which are what you need to ID a fish, apparently. Well, she probably should have said something. Well, she... Like, this is no ordinary mount. Right, she probably should have. Or maybe she did and he just ignored her. He's like, I'm not going to get bossed around by a woman. It's 1938. So she contacts a guy named J.L.B.

8:56Smith, who is an ichthyologist. He's the head of the ichthyology department at a university in Grahamstown and a Ph.D. in chemistry. He's a smart guy, and he's the local fish expert as far as she knows. Yeah, and they're pals. And so she said, hey, I've got this weird-looking fish. And then Smith, his quote was, I told myself sternly not to be a fool, but there was something about that sketch. And apparently it was sketch. She sent him a sketch of the fish to begin with. That seized upon my imagination and told me that this was something very far beyond the usual run of fishes in our seas. And luckily, even though the fish was, I guess, mounted in a traditional form, which, like you said, takes away.

9:44it's how you can identify it. She was able to preserve some of the scales, and somehow from these scales, he was able to say, this is a colacanth, coelacanth. Right. Well, that's what he said at first, and she went, it's pronounced coelacanth. He's like, oh, apparently he said when he saw that scale and identified it positively as a coelacanth, his quote was, if I'd met a dinosaur in the street, I wouldn't have been more astonished. I like that guy. A little hyperbole there, but I like it. So he, I mean, this is seriously, this is like the zoological find of the century and would be for the next 60-something years, right?

10:22Yeah. So he very magnanimously says, you know what? I am going to name this thing after you. And he named it as a new species, Latimeria chelumnae, because, well, obviously her name was Courtney Latimer. Yeah. Courtney hyphen Latimer. Yes. And it was found in the Cholumna River at the mouth of it where it hits the coast off the eastern coast of South Africa. So that's a great name. It's perfect. Yeah. It really puts it in a place in time. So they have now discovered this thing. They realize that they have a big find on their hands. They thought this thing had long been extinct by tens of millions of years.

11:09and so they started to research and, you know, try and learn more about this fish. Yeah. Which is no ordinary fish. No, but I mean, this was, so this was 1938, right? Yeah. And it was the only one that had been found for another 60 years. Yeah. I mean, there's only so much you can find from a stuffed fish, but it did prove, because it had been caught alive, it wasn't like they pulled up a fossil or a dead fish, that had been alive when it was caught. Yeah, I think it was attached to another fish. Oh, really? Like potentially trying to eat it. Oh, okay. Which is one of the, well, not unusual, but interesting things about the coelacanth is that it eats meat.

11:52Well, there's a lot of unusual things about the coelacanth. Yeah. So fast forward another 60 years exactly, in Indonesia, which is on the other side of the Indian Ocean, the eastern side of the Indian Ocean, It was actually first seen in 1997 by a biologist named Mark Erdman, who was in Indonesia doing his Ph.D. dissertation, and he saw a coelacanth in the market. That's crazy. That's a coelacanth. What's that doing here? So apparently he put a bit of a bounty out on it with the locals, and within a year, by 1998, they had brought him a freshly caught one. Yeah, which is quite a task. Yeah, finding a once-thought extinct fish.

12:37Yeah. It's a big one. Well, and we'll get to a little bit why it's even tougher than you would think, too. Sure. So the one that Erdmann found was brown, right? Yeah, it was a little bit different color. Right. The one, like Courtney Latimer described, those are known to be like steel blue. This was brown a little smaller than the one that Courtney Latimer found. And so eventually when Erdmann got his hands on that one, he described it as a new species. Yeah. I mean, it turns out that at one point, you know, hundreds of millions of years ago, there were, you know, potentially over 100 different varieties of this fish.

13:19And they came in all shapes and sizes. These obviously were pretty big, but there were some that were smaller and faster. basically just kind of a wide variety. And as far as we know, I think are these the only two known survivors? Yes. So far. Yeah, the one that Courtney Latimer found are known as the West Indian Ocean coelacanth. Those are the blue ones. They're typically found off of the east coast of Africa, south of Kenya, I believe, down to about the Cormoros Islands. I think they're actually also known as the Cormoros Islands coelacanth because that seems to be where they inhabit the most or the highest density of them is.

14:09Yeah, and some of the weirdos that have, well, we assume that they've been extinct, but you never know. One of them was toothless and over 10 feet long. That was the Megalos coelacanthus. Very appropriately known. Some of them said, forget you, ocean, I'm going to go to the freshwater. So there were actually freshwater coelacanths at one time. And like I said, some of them were slow and ambushed prey. Some were smaller and faster. But they've pretty much universally all been predators from what I've seen. Right. And the two species that are alive today that we know of are, aside from that megalus coelacanth, tend to be a little bigger than the extinct species, which I read is a good example of why they shouldn't be called living fossils, which is what they're frequently called.

15:06Yeah, that's Darwin's term for something that basically never changed. Right. And they've actually studied the genome of the coelacanth and found that they very much haven't changed. And kind of the main reason is they haven't had to. They kind of stayed in the same places. And when you stay in the same places and you eat the same stuff, then maybe you don't change so much. I read the opposite of that, that they have changed enough that they have been evolving. And a good example of that is that they're bigger than they used to be. Oh, interesting. Yeah. But the two species that are alive today, they have traced their genomes back and decided that they've been separated for several million years at least.

15:51Yeah, this one, they finally got the full genome, and they said that it does indeed match the fish's appearance of slower evolution in a journal published in Nature because they have a slower rate of substitution. Gotcha. Basically, the doctor, well, yeah, I guess she is a doctor. It just sounded weird to say that. The doctor? The researcher, who is also a doctor. Yeah. She said it may reflect the fact that they do not need to evolve quickly because they've lived in a relatively unchanging environment where there are a few predators, and they basically haven't needed to change over time like other organisms.

16:30Well, that brings up another thing, too. There's a big question. Why would they just drop off of the fossil record if they've been around this whole time? If they didn't just go extinct 80 or 65 million years ago. The only explanation I've seen is that the places where the fossils turned up were areas conducive to fossilization, like there was a lot of sediment that could turn bone into rock. Yeah. And then the areas that the living species live at now are not conducive to that kind of thing, possibly because they're mostly living around volcanic rock that doesn't necessarily produce fossils. Huh.

17:06You want to take a break? Yeah, let's take a break, and we'll get back and talk a little bit about this funny fish.

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19:59All right. So we've talked a little bit about what makes the coelacanth such an interesting critter. Can a critter be a fish? Yeah. Have you heard of the cuttlefish? That's a critter if there ever was one. Yeah, a cuddly critter. So here are some remarkable things about the coelacanth. They can live as deep. I mean, they're deep water dwellers. They can live as deep as 2 ,000 or more feet. But generally, they think the, I think they generally live about 500 to 800 feet in what they call the twilight zone. Right. Which is still pretty deep. Remember our cave episode? Yeah. That had the same thing.

20:41Remember, there was like organisms that live in the dark, organisms that live in the twilight zone, and organisms that live in the lighted zone. Yeah. These guys live in that threshold between light and dark in the ocean. And they apparently are nocturnal hunters. Yeah, they come out at night, kind of stay hidden. Most of these habitats are caves that they tend to stay in, but there's one off of Tasmania that do not live in caves, and so they have officially been placed on an endangered list because they don't have the protection from bycatch that these other cave dwellers have. Right. That makes sense.

21:20Yeah. So the average day in the life of a coelacanth, at least the cave-dwelling species, during the daytime they're hanging out in a cave. They'll hang out in a cave with, I've seen between up to 12 to 16 other coelacanths. Yeah, have a little coffee. Yeah, maybe just talk. Yeah. You know, talk about their night. And then as night falls, they'll leave their caves and they'll go hunting. And like you said, they're carnivorous predators. They do that passive bycatch thing for the most part, right, where they let the current bring the food to them. but they just basically hang out and wait for a cuttlefish.

22:05It's one thing they eat. Squids, other cephalopods, some fishes, but they seem to not show aggression toward one another from what I understand. Yeah, and while they are passive hunters, they do have an unusual feature, which is, like we said, one of many, but they have what's called a rostral organ, which just means it's in the nasal region and their snout. and it's filled with a jelly-like substance that they think, and they think most of this stuff. I mean, they've done a lot of good studying, but for something so rare, you can't be super sure. But they think that it detects low-level electrical signals and frequencies from prey.

22:47Yeah, like a shark or a ray. Yeah. It's an electrosensory organ where when living tissue contacts water, it can make an electrical impulse that can be picked up. Yeah, and this cool mental floss article is, I think, 11 things about the coelacanth. I can't remember how it was put, but just 11 interesting features. 11 fishy facts. Is that it? Unfortunately. That's why I forgot it. Title aside, it's an interesting article. And one of the things that they don't know why they do, and I have a feeling it has to do with that electrical frequency, is they'll swim nose down for up to two full minutes, which is weird for a fish.

23:30They're just kind of hovering in place, headstanding, right? Yeah. Yeah. And I guess, I mean, if they have that nasal bag of jelly that helps them locate fish, I would imagine that's what they're doing there, right? I imagine it like Tonto holding a railroad track, you know? Yeah. I think it's the same thing, basically. Uh-huh. So when they catch their prey, they eat them. And they can eat stuff that's way bigger than them because, again, which is unique to coelacanths among living things, they have a hinge in their cranium that allows basically their head is convertible. The top of their skull can retract, allowing their mouth to open really wide.

24:15Yeah. So they can eat a large, large cuttlefish. Yeah, and I think that feature also allows their mouth to close with much greater force. With extreme prejudice. Yeah, like when it's unhinged emotionally and physically, it can really close that mouth super hard. They hate themselves for eating cuttlefish. I guess so. They just can't stop. So those are just a couple of the features. There's another is, and we mentioned earlier that the name literally translates into hollow spine. This is because they have what's called a notochord, which is a hollow pressurized tube filled with oil where a lot of fish start this way.

25:01And then they'll eventually get a spine, but this doesn't go away. Right. And not just fish vertebrates. Apparently, there's a lot of mammals that go through this. I think possibly even humans in the embryo. And the coelacanth just says, I'm good with the notochord. I'm going to stick here. Yeah. I'm going to stop here. Which is strange. It is strange. You want to hear some more strangers? I could do this all day. Well, it's a strange fish. Coelacanth, we don't quite understand how they reproduce. And the reason why is because males don't seem to have any sex parts. They don't have junk. They think possibly males grow it when they need it.

25:41but otherwise it's not around. They're growers, they're not showers. Right, exactly. That's exactly right. So we have no idea how they reproduce, but we know that the mode of reproduction is called ovoviviparity, which is however the eggs that the female has get fertilized. Once they're fertilized, they gestate or the eggs develop in the female. Yeah. And then they hatch in the female. Yeah. And then the live fishes continue to gestate. And, like, the whole period lasts, like, three years before they're born. So they go from egg to being hatched to being born within a three-year period. And so, apparently, this does not make the mom, Selacanth, very happy.

26:33And sometimes she will try to eat her newborn pups. Yeah. So supposedly, coelacanth pups, that's what they're called, can dive really deep very quickly the moment they're born. To get away from mom. To get away from their mom, who's like three years. Yeah. Three years. Paging Dr. Freud. Yeah. Yeah, I think sharks may be the only other fish that give birth to live little ones. Is that right? Right. I mean, most fish lay eggs. Right. So it's definitely unusual. Yeah, it may not be unique. But the other thing about their sexy time is there's also a theory that they are monogamists. Yeah, I saw that too.