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Leptocephalus, a transparent eel larva in the wild

A pale liquid in the ocean currents? Plastic pollution? An eel’s ghost? An eel larva! This undulating creature is a large Leptocephalus, a not-often-seen eel in its larval stage. It was filmed by Barry Haythorne and Rob Rutgers while they were scuba diving in Bali.

Leptocephalus, a transparent eel larva
The six-minutes of footage provides a look at the swimming eel larva’s tiny head and face and its long transparent body. More from Scientific American:

You can see through them because their bodies are radically compressed and their organs and muscles vastly reduced. They possess a simple tube gut (the stripe down the middle) and their pane-like bodies are filled with a clear gel. The gel contains glucosaminoglycan (GAG) compounds that will be transformed into adult tissue during metamorphosis.

Leptocephalus, a transparent eel larva
Leptocephalus, a transparent eel larva
According to the Australian Museum, the GAG compounds also store energy for the animal. In their observations of the larva, they suggest that it may be a metamorphosing Rhinomuraena quaesita or Ribbon Eel larva.

Get an even closer look at a transparent leptocephalus in this Enoshima Aquarium clip. Plus: Nautilus Live surprises a Translucent Cockatoo Squid.

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