Eight-eyed eels have mouths full of sharp teeth that file down the skin of their prey and suck their blood to feed on them. (Public Domain)
For more than 150 years, evolutionary scholars have argued that the changes in the body shape of the modern eel (lamprey) over its short lifetime epitomize the “evolution” of invertebrates into vertebrates. However, new research has uncovered fossils that refute this theory. The study was published in the March 10 issue of the journal Nature.
The eel had a long body and a head that resembled a flat circle of suckers with a ring of sharp teeth inside. The eel attaches itself to other fish, using the teeth to file the skin off its prey and feed on their blood.
This is the form of the adult eel, which is a vertebrate that can swim freely around and has eyes. However, their juvenile years are completely different, and for 2-7 years they are invertebrates like anemones, living in the mud of the riverbed, without teeth, not feeding on their own, and living by filtering and retaining the Food that flows through their bodies.
Because the octocoral eel undergoes such a large morphological change in two stages of its Life, evolutionary scholars use it as one of the evidence to prove the theory that organisms evolved from “invertebrates to vertebrates”.
Previously, scientists found fossils of this adult eel from 360 million years ago, which looked similar to modern adult octocoral eels, so scientists thought that the juvenile stage of this fish in ancient times was probably similar to today’s appearance.
Now, scientists have found fossils from the juvenile period of this fish in Illinois, South Africa and Montana, places that thoroughly challenge this theory.
Egg sacs can still be seen on some of the fossils, indicating that these fish were definitely newly hatched juveniles. However, these young fish resemble smaller adult octocoral eels, with all the eyes and teeth suckers. In other words, they are not at all like the juvenile modern octocoral eels.
One of the researchers, University of Manitoba biologist Margaret Docker, said this is an “exciting” discovery, showing that the life of the eel can not be used as “invertebrate to vertebrate evolution”. The life of the eel cannot be used as a “microcosm of the evolutionary process of invertebrates into vertebrates.
Tetsuto Miyash*ta, the first author of the study, says: From genomic, biomedical engineering to evolutionary biochemistry, there is this notion that the eel is a typical representative of primitive vertebrates, and now we have to look at all of this in a new light.
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