For the first time, transparent fish was described in 1856. Then they were considered a separate species. But later research showed that these leptocephali are just one of the stages in the development of acne. It is by the presence of such a larval form that it is possible to classify these fish.
After pecking out of the eggs, the fry for 2-3 months, and in some species even up to 3 years, turn into such transparent larvae. They have rather large teeth, and they themselves grow to a relatively large size, feed. There is evidence that in the deep-sea layers there are three-meter leptocephali, which belong to possibly giant deep-sea eels. In addition, as a result of recent research, it has been found that some transparent fish can reproduce at the exit of the larval stage.