I almost never thought about eels, dismissing them as somewhat boring snake look-alikes that live in the water. So I was intrigued by this article that says that these creatures are very mysterious and it took researchers a long time to figure out the basic facts about them that had stumped scientists from the time of Aristotle through to Sigmund Freud, the main mystery being that however many eels European researchers dissected, until very recently, they simply could not find their reproductive organs. And the reason was bizarre.

People caught eels in brooks, rivers, lakes, the sea. They also caught them, inexplicably, in ponds that dried out and refilled each year, and that had no access to other bodies of water. They couldn’t help but notice that the creatures seemed to have no ovaries, no testicles, no eggs, no milt. That they were never observed to mate. That they sometimes seemed to issue from the earth itself.
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The truth emerged only slowly, and was, in its own slippery way, stranger than the fiction. Careful observers discovered that what had long been taken for several different kinds of animals were in fact just one. The eel was a creature of metamorphosis, transforming itself over the course of its life into four distinct beings: a tiny gossamer larva with huge eyes, floating toward Europe in the open sea; a shimmering glass eel, known as an elver, a few inches in length with visible insides, making its way along coasts and up rivers; a yellow-brown eel, the kind you might catch in ponds, which can move across dry land, hibernate in mud until you’ve forgotten it was ever there, and live quietly for half a century in a single place; and, finally, the silver eel, a long, powerful muscle that ripples its way back to sea. When this last metamorphosis happens, the eel’s stomach dissolves—it will travel thousands of miles on its fat reserves alone—and its reproductive organs develop for the first time. In the eels of Europe, no one could find those organs because they did not yet exist.

There are many other mysteries about the eels that have still to be revealed. But one of the most concerning is why they have become a highly endangered species.

The formerly ordinary, everyday eel is classified as critically endangered, the last official designation on the road toward nonexistence.
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There are many possible reasons, from disease to dams and locks, from fishing pressure to the warming climate, which is causing the ocean currents by which eels make their migrations to shift and change. But there may be other answers, and scientists are racing to find them—a quest that Svensson obviously supports but nonetheless considers not a little tragic. “Those of us who want to protect the eel in order to preserve something genuinely mysterious and enigmatic in a world of enlightenment will, in some ways, lose no matter how things turn out,” he writes. “Anyone who feels an eel should be allowed to remain an eel can no longer afford the luxury of also letting it remain a mystery.”

Saving endangered species is not easy especially if, as with eels, they lack a cuteness factor that rallies the public to their cause.