The European eel is one of the most familiar animals on Earth and one of the most baffling. It wears four completely different bodies in a single lifetime, shows no sex organs until the very end, then swims thousands of kilometres to a weed-choked patch of open ocean nobody can pin down and dies there — without a single person, in all of recorded history, having seen it breed.
The gentlest on-ramp: a four-minute animation following one eel from a speck in the open Atlantic to a European river and back again — a life that runs 'backwards' compared to almost every other fish.
The spine of the whole story: the radically different forms one eel wears in one lifetime — transparent leptocephalus, glass eel, elver, yellow eel, silver eel — and the decades it can spend hidden in a river before the final transformation.
The mystery stated plainly: from Aristotle to Freud, the greatest minds in history could not find eel eggs, eel testicles, or two eels in the act — and, incredibly, we still can't.
In 1876 a 19-year-old Sigmund Freud spent four weeks in a Trieste lab dissecting some 400 eels trying to locate the male gonads no one had ever seen — and left the work quietly beaten.
The obsessive search for the eel's birthplace — including Danish biologist Johannes Schmidt, who spent nearly 20 years crossing the Atlantic chasing ever-smaller larvae until the trail dead-ended in the Sargasso Sea.
A modern research vessel goes looking for the answer with tools Schmidt never had — and shows just how much about the eel's final journey remains genuinely, stubbornly unknown.
Satellite tags on adult eels tracked them all the way to the Sargasso Sea — the first direct proof the destination is real. We now know where they go. We still have never seen what happens when they arrive.