The Anguilla anguilla or European eel has caught the attention of researchers due to numerous attributes like its four stages of transformation. Author Patrik Svensson, driven by fascination over the secretive species, even wrote a natural science memoir describing his relationship with his father, who fished for the enigmatic creature.
The eel has two small pectoral fins and a long body like a snake. They can reach up to 100 years old, beginning with their first stage of life as leptocephalus or flat-shaped larvae.
European eels undergo their first transformation into glass eels, where they become elongated and more translucent. Next, they switch from their ocean habitat to freshwater and become elvers by gaining pigment.
The third transformation results in yellow eels where their undersides resemble the color of lemons and they travel upstream for up to 20 years. They eventually become mature enough to reproduce and have their final transformation. As silver eels, they become metallic colored with big eyes and migrate back to the Sargasso Sea in the Atlantic Ocean.
Aristotle, Freud & Schmidt
According to marine biologist Johannes Schmidt, all European eels come from the Sargasso Sea. Throughout its lifetime, it may travel to other waters all over the world like the Bahamas, Mediterranean, the Black Sea, and Russian waters.
During his travels, Schmidt found larvae on European coasts all the way south in Africa. He realized that the tiny larvae must have been carried by currents.
Even Aristotle was fascinated by the same species, noticing that ponds were filled with eels after the rain. He believed that the European eels grew in mud and humid ground, and may have possibly come out from earthworms.
At 19 years old, Sigmund Freud traveled to the Adriatic coast in Trieste, Italy. He wanted to discover how the species reproduced. After searching hundreds of eels, none had testicles. Until today, scientists still do not know how European eels reproduce.
The reason Freud did not find the eel's reproductive organs is that they would have developed at a later stage of life going back to the Sargasso Sea. It is back in that sea that females lay eggs and males leave their milt. Schmidt wrote, 'The eel's life history is ...hardly surpassed by that of any other species in the animal kingdom.'
Read Also: Snake Eel Escaping From the Fish' Stomach Cavity Burst, What Happened Next is the Grossest Part
Endangered Species
Scientists have not found one major threat to the European eel population but found that the species were affected by dams and hydropower plants. Other threats include global warming, pollution, loss of habitats, and diseases. Fishermen also used to capture the eels for food in dishes like eel pie as well as exporting them to Asia.
Today, they have been listed as critically endangered by the International Union for Conservation of Nature. European eel trade is also monitored by the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
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