Leptocephalus, The Transparent Eel Larva

January 12, 2013


Credit: Mie Prefecture Fisheries Research Institute

Credit: Mie Prefecture Fisheries Research Institute

The marine eels and other members of the Superorder Elopomorpha have a leptocephalus larval stage, which are flat and transparent. This group is quite diverse, containing 801 species in 24 orders, 24 families and 156 genera. They arose in the Cretaceous period 140 million years ago.

Fish with a leptocephalus larva stage include eels like the conger, moray eel and garden eel. The conger eel is the one whose larva was captured by the Mie Prefecture Fisheries Research Institute in Japan.

Credit: Mie Prefecture Fisheries Research Institute

Credit: Mie Prefecture Fisheries Research Institute

Leptocephali have laterally compressed bodies that contain jelly-like substances on the inside, with a thin layer of muscle with visible myomeres on the outside. They have a simple tube as a gut. They have dorsal and anal fins, but they lack pelvic fins. They also don’t have any red blood cells, which they only begin produce when the change into the juvenile glass eel stage. They also possess fang-like teeth that are present until metamorphosis, when they are lost.

Leptocephali differ from fish larvae because of their size and their long larval periods, which last between three months to more than a year. Their anguilliform swimming motions allow them to move forwards and backwards. They appear to feed on marine snow, tiny free-floating particles in the ocean.

[via Twisted Sifter]


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3 Responses to “Leptocephalus, The Transparent Eel Larva”

  1. Madanagopal.V.C Says:

    The transparent Eel larva reminds me of the transparent jelly fish which also belongs to the cretaceous period 140 million years ago. Probably there were not much predators for these fishes in the early period, they themselves feeding on free floating particles. Even human beings at the embryological stage are transparent only. They add pigments and hair later on to face the environment in their later life. Red blood corpuscles are required to transport oxygen from lungs whereas the fish can breath through their gills by drinking dissolved oxygen in water.


  2. jake Says:

    can it develope inside you possibly


    • Evan Says:

      Not at all. No more than kittens or oranges can develop inside you.

      They have to breathe, live in seawater, and can only eat bits of plankton and other marine debris. Unless you also have a large ocean and sunlight inside you, you can not host these. If you swallowed one, you would digest it (and people do eat eel!)

      They do superficially look vaguely like certain parasitic worms, so I can see the reason for your question, but they are not biologically parasites.


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