No one can figure out how eels have sex - Lucy Cooke

From Ancient Greece to the 20th century,
Aristotle, Sigmund Freud,

and numerous other scholars were all
looking for the same thing: eel testicles.

Freshwater eels, or Anguilla Anguilla,
could be found in rivers across Europe,

but no one had ever seen them mate.

And despite countless dissections,

no researcher could find eel eggs
or identify their reproductive organs.

Devoid of data, naturalists proposed
various eel origin stories.

Aristotle suggested that eels spontaneously
emerged from mud.

Pliny the Elder argued eels rubbed
themselves against rocks,

and the subsequent scrapings
came to life.

Eels were said to hatch on rooftops,
manifest from the gills of other fish,

and even emerge from the
bodies of beetles.

But the true story of eel reproduction
is even more difficult to imagine.

And to solve this slippery mystery,
scholars

would have to rethink
centuries of research.

Today, we know the freshwater eel
lifecycle has five distinct stages:

larval leptocepheli, miniscule glass
eels, adolescent elvers,

older yellow eels, and adult silver eels.

Given the radical physical differences
between these phases,

you’d be forgiven for assuming these
are different animals.

In fact, that’s exactly what European
naturalists thought.

Researchers were aware of leptocepheli
and glass eels,

but no one guessed they were related
to the elvers and yellow eels

living hundreds of kilometers upstream.

Confusing matters more, eels don’t
develop sex organs until late in life.

And the entirety of their time in the
rivers of Europe

is essentially eel adolescence.

So when do eels reproduce,
and where do they do it?

Despite its name, the life of a freshwater
eel actually begins

in the salty waters of
the Bermuda Triangle.

At the height of the annual cyclone
season,

thousands of three-millimeter eel larvae

drift out of the Sargasso Sea.

From here, they follow migration
paths to North America and Europe––

continents that were much
closer when eels

established these routes
40 million years ago.

Over the next 300 days, Anguilla Anguilla
larvae ride the ocean currents

6,500 km to the coast of Europe––

making one of the longest
known marine migrations.