MadSci Network: Evolution

Re: Did the eel evolve from another fish?

Date: Tue Apr 27 08:23:29 1999
Posted By: Ingrid Dodge, Grad student, Immunology, Harvard University
Area of science: Evolution
ID: 924210177.Ev

Dear TJ-

Thank you for your fantastic questions!  I had a lot of fun
finding out more information on eels for you.  First of all,
let's talk about the moray eel, and then go on to the 
electric eel.

The moray eel is a member of the class osteoichthyes.  This 
literally means bony fish (osteo=bone and ichthy=fish).  All of 
the bony fishes, from eels to seahorses to flounder and salmon, 
are ultimately descended from more primitive nonbony fishes, like
sharks.  If you'd like a more detailed answer, please e-mail
me back and I'd be happy to tell you about it. :)  There are 
also some fantastic pictures of moray eels on the web, if you
want to take a peek at them.  My favorite is:

Now onto electric eels (otherwise known as Electrophorus electricus to
scientists).  Electric eels live in murky habitats and use their 
electric shocks to protect themselves and catch prey.  They can 
generate up to 600 volts of electricity (which is about 5 times as 
much electricity as comes out of a wall socket), which is enough to
seriously stun or even kill a person.  The way that they generate this 
electricity is fascinating.  Most of the eel's body, which can range
from 3-9 feet long, is taken up by a series of specialized cells called
electrocytes.  Each electrocyte acts like a little battery, but can
only generate 80 millivolts.  If you link up enough of these cells, 
though, like you link up a series of batteries to run a portable radio,
the eel can deliver quite a shock.  Electric eels have 5000-6000 of
these specialized electrocytes, which take up most of the eels body.
The head of the electric eel acts as the positive pole of the battery, 
the tail the negative end.  When it touches its head and tail to its
prey or to a predator, it delivers an electric shock.  Electric eels
have no teeth, so it helps the eel to swallow its food if the food is
shocked and not moving.

Some people even believe that electric eels use their electricity
to communicate!

I hope I've answered your questions, thank you for such good ones,
and if you have any other questions, please don't hesitate to ask!

Have a wonderful day!
Ingrid Dodge :)

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