Hi Bill,

I'm not a fish person, but I do know Christina Cox-Fernandez, who has done quite a bit of work on electric eel diversity and evolution. Here's the link to her departmental website at University of Massachusetts-Amherst:

http://www.bio.umass.edu/biology/about/directories/faculty/cristina-cox-fernandes

I hope this helps.

I think the question you are asking could be answer in 2 way.

1. How ?

You have to do genetic mapping of eel ans then have to look for the gene responsible

2. How they are selected or what selection pressure was acting.

That would be answers by looking at the use of the electric eel's ability and some ecology and field experiment would prove that.

You can also do the common garden experiment with the 2 closely related eel and give them a common garden feature or if we already know the gene or organ need for electric generation , you can make the organ non-functional and look for the changes in the behavior and benefits reduction and hence we can come to know that what selected the eel in the natural population

Thank you Patrick. I have been in touch with Cristina and she has pointed me towards some reference works which I am going to pick up today. Thank you Chandan. I haven't the means for doing what you advise, but I appreciate the direction and input.

Excellent that you've been in touch with Cristina. She's done great work. Glad my message helped a bit.

P

If you look at a family tree of fishes, the electric eel isn't that unique. Many, many members of the Gymnotiformes (the South American knife fishes, and the group that also includes the electric eel) have electrogenerative capabilities, but in most cases these electric charges are minor and mostly used in sensing the environment. The electric eel is unique in that it has taken this sensory adaptation and modified it into a form of prey capture.