There are over 200 species of deep-sea anglerfish; some are long and thin, some are squat and round, some have fins that they use to "walk" along the sea floor, and others have huge eyes set far back into their heads. But how did all this morphological diversity first come to be? Thanks to a new anglerfish family tree, now we know. Scientists built this evolutionary tree using genetic information from hundreds of samples and anglerfish specimens across the globe. It indicates that anglerfish originated from an ancestor that crawled along the seafloor ... and sheds new light on how experts could think about biodiversity as a whole.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What is the anglerfish and its significance in the deep sea?
You're listening to Shortwave from NPR. The first time I ever saw an anglerfish was on the big screen. It appeared first as a warm, glowing light. I see a... I see a light.
A light?
Yeah, over there.
Oh, I see it too.
Rising out of the dark with bulbous eyes and pointy teeth, this fish gets a villain moment in the 2003 Pixar movie Finding Nemo. It's so pretty.
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Chapter 2: What was the anglerfish scene in Finding Nemo?
Good feelings gone.
And so ensues probably the best underwater chase scene in cinematic history.
I remember seeing this movie in the theaters. I was three in 2003. This is Rose Fauché from Rice University. And apparently when the anglerfish scene came on, I was so freaked out by it, I started crying and my mom had to take me out of the theater.
But Rose has had a change of heart about anglerfish because this past year, she did research about them alongside evolutionary biologist and ichthyologist Elizabeth Miller at UC Irvine. Now, Elizabeth says this moment in Finding Nemo, where Dory and Marlin are enthralled by the anglerfish's bioluminescent light, is pretty accurate to how it happens in the deep sea.
The idea is that the prey are drawn to the lure and they don't see the anglerfish attached to it and they get eaten.
There are over 200 species of deep sea anglerfish. The one in Finding Nemo was modeled after what's known as the football fish. But Elizabeth and Rose told me others look very different. Some are long and thin, like eels. Some are squat. Some have huge prehistoric looking teeth, while others have big eyes set far back into their heads.
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Chapter 3: What are the different species of anglerfish?
And the majority of them live in the bathy pelagic zone, the deep deep sea.
It's a huge expanse of space in total darkness, high pressure, cold temperatures, food limitation.
But in this zone that is so cold, so homogenous, and so devoid of sunlight, somehow the anglerfish still ended up looking very diverse. And researchers wanted to know why.
It is a mystery. It's not clear why one anglerfish species would be shaped one way and while a different anglerfish species would be shaped a different way.
Chapter 4: Why do anglerfish look so diverse?
So today on the show, the big anglerfish mystery. Why do these science fiction-y fish look so different from one another? What spurred this divergence in anglerfish body shape and size? And what can that tell us about the deep sea as a whole? I'm Emily Kwong, and you're listening to Shortwave, the science podcast from NPR.
I'm Tanya Mosley, co-host of Fresh Air. At a time of sound bites and short attention spans, our show is all about the deep dive. We do long-form interviews with people behind the best in film, books, TV, music, and journalism. Here our guests open up about their process and their lives in ways you've never heard before. Listen to the Fresh Air podcast from NPR and WHYY.
On the Indicator from Planet Money podcast, we're here to help you make sense of the economic news from Trump's tariffs. It's called in game theory a trigger strategy, or sometimes called grim trigger, which sort of has a cowboy-esque ring to it. To what exactly a sovereign wealth fund is. For insight every weekday, listen to NPR's The Indicator from Planet Money.
All right, Rose and Elizabeth, the deep-sea pelagic anglerfish, what were the big question marks for you, and what did you want to figure out?
So we can look at images of anglerfish, and it seems obvious to our eyes that they're different shapes, but we needed to... to quantify that variation so that we can analyze it in an evolutionary framework. And what I mean by an evolutionary framework is understanding how all of that diversity evolved. Did it evolve very quickly? Did it evolve gradually?
Those are the big questions. And Rose, at the time, you were an undergrad student at Rice University in Elizabeth's colleague's lab. Can you explain what you did on this project? What was your role?
So my part of the project was... looking at the morphology of anglerfish skulls. I had to look at the skeletons of the anglerfish and then determine which bones are which and like the edges of all the bones and things like that. So I took the CT scans that we had of these anglerfish and And first I had to make them into like a 3D model.
And then we have this very fun software that basically lets me put a little dot on certain points of that skull model. We settled on, I believe it's 111 landmarks that I put onto each of these skulls.
Yeah, I will say 111 points is a lot. It's even more difficult when you've got these fish that have such bizarre skulls. The work that Rose did is really tremendous, and it was all done by hand.
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Chapter 5: How did researchers study anglerfish morphology?
That's correct. And finding the fish is no small feat, as you can imagine. It relies on careful planning of people who regularly go out to sea. to do surveys of fishes in general, not necessarily targeting anglerfishes, and making sure when an anglerfish is found that it's preserved in the proper way. It needs to be kept on ice and kept cold pretty much as soon as it's brought up.
It needs to be preserved in alcohol and put on a shelf in a museum. And that's the basis of the CT scans or the three-dimensional x-rays that we used. And then the tissues were the basis of the Family tree.
Okay. So while Rose was mapping all these three-dimensional x-rays, plotting points onto the skulls to see where the anglerfish were visually similar, it sounds like, Elizabeth, you were extracting the DNA and seeing where they were genetically similar.
That's right. That's exactly right. And so from there, I use fancy statistical models and basically it tells me what the differences are from species to species and the significance of those differences as far as like how closely or distantly related the different species are.
Wow. Okay. Rose, can you talk a little bit about how you and Elizabeth got access to all these specimens and CT scans? I heard all this was done with museum collections, kind of like... an interlibrary loan, but for museums?
So all these different museums across the world have like fantastic collections of fish that are basically just preserved in ethanol. And there is like an online database where you can search for, you know, whatever species of fish you're looking for and it will show you. And the fish world is actually, it's pretty small. It feels kind of like everybody knows everybody.
And so if you ask nicely enough, They'll FedEx you fish that have been sitting in a jar since like 1965. And if you're a very lucky undergrad, you get to open up a package in lab one day and you're holding like one of the rarest fish on earth. Were you one of these lucky undergrads who got to do this?
I did get to be an undergrad who opened up a box from FedEx one day and there's a football fish, you know, wrapped in cheesecloth, soaked in ethanol. And I picked up the fish and I was so excited. I ran down the halls of this building to like go and show all of my friends that I had a football fish.
Also, I'm sure it's, you know, shocking to hear, but 60-year-old fish sitting in ethanol do have a particular smell about them. Delicious.
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Chapter 6: What challenges do scientists face in anglerfish research?
I'll give some context that anglerfish, the deep sea anglerfish we've been talking about, are all part of this group with a scientific name, Lopheiformes.
Lopheiformes. Yes. Okay.
So the deep sea anglerfish, their closest relative within this broader group is a fish called the sea toad the sea toad yes that's another fun one to google if you if you have access to google the um sea toad oh i am i am coffin fishes is that another word for sea toads yeah they look very grumpy they're literally frowning
Exactly. And hanging out on the bottom of the ocean floor.
Yep. Coffinfish is another word for them. So that's the closest relative, the closest living relative to the deep sea anglerfishes we've been talking about. And so what did the direct ancestor of the anglerfishes look like? It most likely looked something like that sea toad, although perhaps something intermediate. We can't know for sure, but what it implies is that
The broader group, Lophiformes, has always been in the deep sea in some capacity. But the more significant transition was off the seafloor and into the water column.
Yeah. This seems like one of the biggest takeaways of your study. And it's amazing that anglerfish started from an ancestor that lived on the ocean floor and then made it into the water column to be the anglerfish that we know and love today.
That's correct. The bathyplagic anglerfishes seem to have arisen from a deep-sea benthic ancestor, and it was this transition off the seafloor that spurred the evolution of all of these new shapes.
And what does that tell us about the conditions of this part of the ocean that made that so? Is it just that they had to adapt super quickly in order to survive?
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