This Week in Zoology: WTF Is That?!

This video has been reposted by quite a few of my friends, with twin exclamations of “Wow! How cool!” and “What the Hell is it?!”


Well, do you know what it is? Care to take a guess?


That odd, mystical creature is actually the larval form of an eel. A large moray eel leptocephalus, to be precise.

Here, look at a picture close up, and you can see it’s little eel face

A large moray eel leptocephalus in shallow water, Bali, 18 April 2010.

A large moray eel leptocephalus in shallow water, Bali, 18 April 2010.


For years, people thought that eel larvae were an entirely different creature, before realizing that they were simply the larval stage of a well known fish. That is why Zoologists keep referring to eel larvae as “leptocephali”, which was their name when they were thought to be a different species.

It was an honest mistake to make, given how eels have one of the most complicated life cycles in the fishy world, which still has some large gaps in it.

Some marine eels migrate thousands of miles in the open ocean to return to their spawning grounds. Others oscillate between freshwater and saltwater during their life cycle, inhabiting a coast, an estuary and a stream in different stages of their lives. They undergo dramatic body transformations not only once, but multiple times in their lives, from leptocephali, to glass eels, to juvenile eels, to adults, and even the migratory adult eel can look completely different with larger eyes, different pigmentation and no gut. Given all of that, it’s no wonder that people didn’t make the connection and realize they were observing different stages of the same animal.




  1. Great American Satan says

    That is damned amazing. The face is brilliant. Imagine if humans were this weird. a two year old with a tiny grown man face and a paper thin transparent body, living in NYC while parents live in Death Valley and couldn’t even guess how many of the freaks they let out. I also goog image search’d glass eels. They are rad and horrible. HP Lovecraft’s marine phobias gain more justification all the time.

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