You're listening to Shortwave from NPR.

Hey, Shortweaver is 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.

Arian Paulstra is a fish physiologist at Waganning 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 donuts of eel,

but never found him.

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 Johanna Schmidt.

Over multiple sea voyages, Danish biologists Johanna Schmidt would eventually trace

smaller and smaller eel larvae to the Sargasso Sea in the middle of the Atlantic Ocean.

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