GoKawiilUntil recently, nobody knew how eels reproduce. On August 14, 2021, TikTok user ColeTheScienceDude published a video named We Don’t Know Where Eels Come From. The user shares information about how little is known about the eel species Anguilla anguilla, also referred to as freshwater eels or the European eel, reproductive cycle.
He says, “We have been to the moon, and yet we still do not know how eels sexually reproduce.” The user then describes more qualities of eels that experts find puzzling, including: “If you dissect one and you look inside, you will not find sexual organs.” He added. “We have never observed eels mating in captivity or the wild.”
Most Anguilla anguilla eels lack reproductive organs; however, scientists can bring them to sexual maturity by treating them with hormones. With hormone treatment, eels can be brought together in captivity to reproduce.
In the wild, however, during the last phase of their complex life cycle, they do develop reproductive organs. This final stage is known as the silver stage, and during this stage, the eels’ stomach dissolves before their sexual organs develop. This means the eels die soon after reproducing, which has made the mystery of eel reproduction even more challenging to work out.
Born in the remote Sargasso Sea, these eels begin life as transparent larvae, resembling tiny leaves with fish heads. Carried by Atlantic currents, they embark on a voyage spanning thousands of miles, eventually reaching the shores of eastern Europe. Here, they transform into bootlace-sized young, known as glass eels or elvers.
As they mature, they settle in shallow coastal seas, undergoing another transformation into yellow eels, marked by a change in color and habitat as they migrate into rivers and lakes. They can stay in these inland waters for decades, silently growing and waiting.
Finally, they enter the silver stage, retracing their paths back to the Sargasso Sea, where their reproductive organs develop, culminating in a life dedicated to this ultimate journey.
The First Direct Confirmation of a Crucial Stage of the Eels’ Life Cycle
After decades of speculation, researchers have successfully tracked European eels back to their breeding grounds in the Sargasso Sea, following their journeys thousands of kilometers along one of nature’s most incredible animal migrations.
Scientists are ecstatic because this is the first confirmation of a long-suspected stage of the eels’ life cycle, which was proposed about 100 years ago. Fish biologist Kim Aarestrup from the Technical University of Denmark, the study’s author, stated on Twitter that “eels have piqued the curiosity of scientists for millennia.”
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