TGIF: Eel larvae

The larvae of eels and other related species are called small heads or in the fancier Greek, Leptocephalus.  The video above should give you some insight into this moniker.  Unlike fish larvae, Leptocephali can grow quite large from a few inches to well over a foot in length.  Also unlike fish larvae, Leptocephali do not feed on plankton but rather feed on microscopic particles in the water called marine snow. As can be seen in the video above they are transparent, undoubtedly an adaptation to avoid predation.  Indeed, Leptocephali do not possess red blood cells which could be easily seen in a transparent body.  Red blood cells are not acquired until the next phase of their life.

Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

6 Replies to “TGIF: Eel larvae”

  1. awesome video! I’m work with American eels for my master’s degree so I love seeing other leptocephalus larvae!!

  2. Wow! Thanks for that clip, biology is endlessly fascinating.

  3. I thank the person who took the picture of the live leptocephalus. It is really wonderful to be able to see a live, gracefully moving transparent leptocephalus as a past researcher on leptocephal. I saw leptocephali hatching from the eel eggs about centimeter long and alive for a few days and finally died in the lab glass containers. But this picture really great and I have never seen anything like this before.
    Thank so much for feasting my eyes. I wolul like to forward this to my fellow leptocephaloligists. Solomon

  4. After posting the comment on the beautiful leptocephalus, I was tempted to identify the leptocephalus as a past researcher on them. It looks like it is the leptocephalus of a Muraenid, such as a Moray eel. The environment also is suggestive of Moray eels. I could be wrong as this is not based on the scientific data such as the myotome count etc. Good luck to others who might like to take a guess.
    Solomon Raju.

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