The Weird World of Larval Fish (2016)

The ocean can be a wondrous place full of phantasmagorical creatures, and some of the strangest marine life can be seen in the highly modified juveniles of certain fishes—the paper-thin undulating ribbon of an eel larva; the tiny, spiky sphere of a sunfish; the dorsal fin floaties of a basslet; or the diaphanous veil of a ribbonfish. Let’s explore the weird world of fish larvae…

Eels offer one of the strangest examples for how to build a baby fish. When first discovered, these transparent creatures were described as their own genus (Leptocephalus), and when it was eventually determined that they developed into eels, it was suggested that the largest specimens (said to measure 1.8 meters) might eventually grow into a 30 meter adult eel.

Source: reefs.com