electric eels and their means of shocking

[liambob1]

I find the ability of electric eels to use electricity offensively confusing. I can understand that it can achieve a separation of charge within an electric organ through biological processes in which I'm not very interested just now. According to some vague descriptions of how it works, it then "discharges" or "fires" the organ. I presume what this means is that it allows the organ to return to equilibrium, with a strong current briefly flowing through the organ itself. But how does this cause the target fish to be electrocuted?

 

I would greatly appreciate it if anyone can offer an explanation of the physical processes occurring here, or direct me to somewhere where I might read more about it.

[Moontanman]

Electric eels are not my personal cup of tea but mormyrids are which use electricity in a similar manner to navigate and communicate with each other, many other fish use electricity on a smaller scale. Mormyrids do not hunt with electricity but I've observed them using their electricity as a means of aggression against other fishes. The electric fish creates a electric field around it's body and anything that comes in contact with the field distorts the field and the fish can use this effect to navigate and to sense the presence of each other, other fish and obstacles. Mormyrids have a larger brain to body ratio than humans, they interact with each other in complex ways not completely understood. Mormyrids use this effect to maintain position in schools in very black or muddy water. Most electric fish are functionally blind. Electric eels can also use this electricity to shock other creatures that come within range. This wiki link explains it in more detail than i can...

 

 

 

http://en.wikipedia.org/wiki/Electric_eel

Edited August 18, 2010 by Moontanman

[liambob1]

I understand that, but that doesn't explain and nor as far say I can see does that page describe how the eel released the charge into the water and thus into its prey. it is not the details of the biological processes that I don't understand , but how that results in a current flowing in the target fish.

 

My thinking is as follows:

Firstly, I don't think it releases ions out into the water.

 

Secondly, suppose it releases positive ions from one end of the organ. The negative charge that is still in the other end of the organ will be exerting a very large force on them and they will be pulled back to that part of the eel. The target fish has net charge of 0, so it wouldn't pull the charged particles towards it.

 

All help is greatly appreciated

Edited August 18, 2010 by liambob1

[Moontanman]

Good question, I have always looked at it from the stand point of an electrical field and when the lines of the field are cut by prey or an enemy the eel ramps up the field and this results in extreme muscle contractions in the victim. When an elephant-nose fish, mormyrid, uses it's electricity as a means of aggression it flicks it's trunk in the direction of the object of it's aggression and the victim jumps like it's been shocked, almost like it is generating an electrical wave. I know that electric catfish can make you tingle or simply shock you causing muscle contractions, I've never been shocked by an electric eel.... I'm quite certain no ions are released into the water... But the fewer ions in the water, salts, the more current is necessary to generate the field, electric marine rays only generate a 100 volts or so but can knock you for a loop... electric eels live in water that can be quite soft and has few ions so it has to generate a much stronger field. The field of electric fish can be converted to sound by a simple device and each fish has it's own sound, a peculiar buzzing to rapid fire clicks...

Edited August 18, 2010 by Moontanman

[liambob1]

That would indeed be a possibility. However, in order for it to occur in that manner, for the electric field to remotely force a current through a target fish, the voltage across the organ would need to be enormous. I have read that they are capable of creating potential differences of a few hundred volts, this is far too low, I believe.

[Moontanman]

That would indeed be a possibility. However, in order for it to occur in that manner, for the electric field to remotely force a current through a target fish, the voltage across the organ would need to be enormous. I have read that they are capable of creating potential differences of a few hundred volts, this is far too low, I believe.

 

 

I think experiments would have to be done to confirm or deny your belief and I am pretty sure they have been done, the field can be measured or even heard by converting it to sound, the amperage is as important as the voltage and electric fish can indeed generate muscle contractions from a distance for sure...

[liambob1]

Clearly, but what I propose is not that the eel doesn't work. It is obvious that it does. I think there is a different explanation for it than just that the electric field surrounding the eel in a usual dipole shape is powerful enough to force a current through another fish.

 

Furthermore, your wording seems to indicate that when people talk about "firing" the organ, they mean that before this, it was at electric equilibrium, and then it "fires" by the eel separating the charges in just a few seconds. That would require the eel to produce a gigantic amount of energy in a very short period of time. I was under the impression that it gradually built up the separation over time, if this is indeed the case and the electric field surrounding it can produce a force strong enough to drive a current through a remote target, then it would constantly be electrocuting everything around it, which I don't think is the case.

 

So, if it is the case, as you suggest, that the eel electrocutes things just by becoming a dipole and the electric field around it is strong enough to force a current through other fish, then one of the following must be true:

 

1 - There is no "firing" of the organ (The fact that I have seen reference made to this "firing" or "discharge" in a number of places makes this seem unlikely) and the eel produces an extremely high potential difference within itself.

 

or

 

2 - Usually, the eel is at electric equilibrium, it only separates charges when it is attacking. This would require the eel to produce a huge amount of energy very quickly, and it would be incorrect to call this a "discharge," because it is going from an uncharged state to a charged state.

[Moontanman]

The electric eel much like other electric fish fire their electrical organ continuously at a low level, only ramping up the field when it wants to shock a fish or other creature. The organ generates electricity as needed all the time, an electric eel can fire at a level powerful enough to kill over a hundred times with out running out of energy, it's continuous navigational field is firing all the time.... the individual firings are so close together they sound like a buzz when converted to sound waves.... the buzz generally never stops it just speeds up and slows down....