Eel-Is it male or female?

Eels baffled Aristotle, the ancient Greek philosopher.

However much he examined these smooth-skinned, snakelike fish, he found neither sex organs nor eggs.

“The eel,” he said, “is neither male nor female, and can engender nothing.”

He concluded:

“Eels are derived from the so-called ‘earth’s guts’ that grow spontaneously in mud and in humid ground.”

Modern researchers have solved this particular mystery about the eel.

Christopher Moriarty of the Department of the Marine in Ireland explains that while most fish show very distinct eggs, the eel shows no sign of even a small egg.

“The ovary of the eel,” he says, “is inconspicuous—almost invisible in young specimens, and forming no more than a whitish, frilled ribbon in more mature ones.”

Since no spawning eel has ever been caught, even up to modern times, you can understand why Aristotle was puzzled.

Not having a microscope, he had no way of finding out where eels came from
While scientists have solved this particular mystery about the eel, they have uncovered others that are still puzzling.

The Mystery of Its Origin

Each spring, millions of tiny eels two or three inches long [5-8 cm]—called elvers—arrive near the shores of Western Europe and North Africa.

Where do they come from? Until the 1920’s, no one knew.

However, near the end of the 19th century, a startling discovery was made that contributed to a solution of this mystery.

It was observed that the eel, like the frog and the butterfly, starts life in a different form.

Biologists discerned for the first time that a slim, transparent fish called leptocephalus, with a tiny head and a body shaped like a willow leaf, metamorphosed, or changed form, to become a tiny transparent larva called a glass eel.

Once the connection between the leptocephalus and the glass eel was made, it was possible to track the eel larvae back to their source.