By: Caden Kipfmueller

Freshwater eels are widely regarded as one of nature’s great mysteries. The gender and reproduction habits of this species have perplexed scientists and great thinkers alike for centuries. Ancient Greek philosopher Aristotle was famous for his belief that eels did not conform to gender in the same way that most species of fish do, and Sigmund Freud once was pushed to the brink of insanity when hundreds of dissections led to absolutely no new information on the topic.

Eels are one of the few species of animal that still has more questions than answers in modern biology, and it has taken most of human history to produce what still amounts to an incomplete understanding of the creature.

The lack of information that scientists have about eel reproduction is extensive. Eels have never been observed mating, either in captivity or the wild. Additionally, sexual organs have never been spotted on the eel at any stage of its life. Given the abundance of the species and its prominence around the world, this is an unprecedented phenomenon, and one that has never occurred before. Naturally, there is a great degree of speculation regarding how exactly more eels are made, but the most widely accepted theory is rather strange.

As the current scientific consensus agrees, freshwater eels begin their lives in the Sargasso Sea, a part of the Atlantic Ocean that is almost a highway of ocean currents, all going in different directions. At this time, scientists do not know why specifically the Sargasso Sea is the point of origin for eels, but the youngest eel larvae recorded have been located there. From the Sargasso Sea, eels begin to migrate to other parts of the world, swimming to freshwater locations by going against the current in rivers.

During this process, the eels undergo a variety of metamorphoses, the first of which is the transition from larvae to glass eel (a stage in the life of an eel named after the almost see-through pigmentation they take on during this phase). Once the eel has found a home in freshwater, it will settle. Life doesn’t change much for eels at this point, but they do still undergo some additional metamorphoses.

After an indeterminate time, the eel reaches what scientists regard as mating age. This age is different for every individual eel, and the range for when it could occur is dependent on a variety of factors in the eel’s environment. Upon reaching maturity, the eel heads back to the Sargasso Sea to mate, dying shortly after. As said before, scientists do not know exactly how eels mate, just that sexual organs likely develop during an additional metamorphosis to prepare for reproduction.

Ultimately, the freshwater eel is still very much a creature shrouded in mystery. It may be hundreds more years before more information is discovered about them, but given the recent rate of discovery in science, many feel like it is just a matter of time before the secrets of the eel are eventually revealed.