Prepare to be baffled by what we don't know about eels
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What is the main topic discussed in this episode?
This week on Consider This, the drama at CBS News. Some of the most respected journalists in America say their corporate ownership is bowing to political pressure. It's intimidation. They've created a climate of fear to make the news organization unwilling to tackle the problem and report the news. Longtime 60 Minutes correspondent Steve Croft, this week on Consider This. Listen on the NPR app or wherever you get your podcasts.
You're listening to Shortwave from NPR. Hey Shore Wavers, Regina Barber here with a modern day eel mystery. To this day, no one knows where they come from. Well, not entirely. Centuries ago, people thought that baby eels just sprang up spontaneously from morning dew.
Or from mud or from slime. So they thought it was not like an animal that was reproducing, which just started to exist spontaneously from something.
Arjan Palstra is a fish physiologist at Wageningen University and Research in the Netherlands. He says eventually people started looking for eel reproductive organs like gonads to convince the world that spontaneous generation wasn't happening.
Even a big name like Sigmund Freud, he started his career by looking for the gonads of eel, but never found them.
A couple decades later, somebody found an adult eel in the ocean, sex organs and all. And that part of the mystery was solved. But still, no one knew where they went to make baby eels. All they knew was that decades-old eels living in rivers would swim out to sea and never come back.
Somewhere in the 1890s, Italians discovered larvae were found in the seas around Italy. And that was basically the starting point for Johannes Schmidt.
Over multiple sea voyages, Danish biologist Johannes Schmidt would eventually trace smaller and smaller eel larvae to the Sargasso Sea in the middle of the Atlantic Ocean.
That's where he found larvae. And at that moment, that was the most indirect proof that eels must be spawning right there in the Sargasso Sea.
Then a century went by with no major breakthroughs, until the late 2010s, when scientists attached satellite tags to a couple dozen eels by a chain of Portuguese islands in the Mid-Atlantic. When the trackers were recovered, they showed the first direct evidence that adult European eels go to the Sargasso Sea to spawn. But to this day, no one has found a mature eel in the act of spawning in the Sargasso Sea, a 2 million square mile area.
What mystery surrounds the life cycle of European eels?
We're talking about going to Mars, but in the meantime, we don't know many things of our deep seas.
That discovery could help explain why eel populations have declined and guide ways to raise them in captivity, which could boost eel numbers in the wild and decrease illegal trafficking. Today on the show, the hunt for the spawning grounds of the European eel. Plus, a look at their quirky lives and what solving this mystery would mean for the future of the species. I'm Regina Barber, and you're listening to Shortwave, the science podcast from NPR.
This week on the NPR Politics Podcast, catch up on the week's big primary election news, how things played out with newly drawn districts in California and an increasingly competitive Senate race in Iowa. Plus, we unpack the latest redistricting news that may benefit Republicans in the fall. Listen every afternoon to the NPR Politics Podcast. Find us on the NPR app or wherever you get your podcasts.
So, Arjan, why have scientists still not found a European eel spawning in the Sargasso Sea?
That's a very good question. It may have to do with the fact that they don't have a specific site where they spawn. For instance, Japanese eel that spawns in the Mariana Ridge, we know that they do that near seamounts.
How did historical beliefs about eel reproduction evolve?
And they do that in upwelling areas near seamounts and also at a specific time, at noon moon. So if you can pinpoint where you have to be and at what time, then you may be able to catch them in the act of spawning. And Professor Tsukamoto, he has done that already back in the 90s for the Japanese eel. But for European eels, they swim to the Segasu Sea, but not to a specific site.
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Chapters
5 chapters
1
What is the main topic discussed in this episode?
0:00–2:45
2
What mystery surrounds the life cycle of European eels?
2:45–4:17
3
How did historical beliefs about eel reproduction evolve?
4:17–12:21
4
What evidence suggests where European eels spawn?
12:21–13:00
5
Why is the Sargasso Sea significant for eel reproduction?
13:00–14:50
Speakers
3 identifiedMore from Short Wave
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