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Science & Environment

Electric Eels Jolt Their Prey By Remote Control

SCOTT SIMON, HOST:

Electric eels are pretty amazing. I wonder if they feel the same way about us? 80 percent of the body of an eel is made up of cells that are a lot like batteries. And those batteries can deliver shocks of up to 600 volts - that's enough to knock you over, if you ever got in the way of an electric eel, which is something that a fish is more likely to do.

Neurobiologist Ken Catania has been studying the Amazonian fish in his lab at Vanderbilt University. He joins us now from the campus at Vanderbilt in Nashville.

Thanks very much for being with us.

KEN CATANIA: Thanks. It's great to be here.

SIMON: So what's going on? It's more than just an eel sees dinner, delivers a shock and then eats it, right?

CATANIA: Yeah and actually, that's what I thought would be happening originally, until I started looking in more detail. So these eels are really fast and so to see what was going, on for starters I had a put them under the high-speed video system and slow their motion down. And when I did that, I saw that the eels are capable of completely freezing up their prey in about three milliseconds.

SIMON: With an electric jolt?

CATANIA: Yeah. The eel gives off high-voltage pulses and it turns out that each pulse is activating a nerve to cause an impulse in the nerve that leads to the muscles. So this is really sort of a form of remote control of the prey's nervous system. So eels give off, in addition to this big zap to immobilize prey, they also give off these little doublets periodically when they're hunting. And that has the opposite effect of the immobilizing output. That actually causes a massive whole-body twitch in hidden prey.

SIMON: Why does the eel give off this initial volt that kind of stuns the fish, as opposed to just going for the jugular?

CATANIA: You have to transport yourself to the Amazon and imagine that this is a nocturnal animal, it's searching for prey in what may be murky water and the prey are usually going to be hidden somewhere. And so if it's near what it thinks might be something it can eat but it's not sure, all it has to do is give off this pair of high-voltage pulses and that animal is going to twitch. And the eels are very sensitive to water movement, so that will allow them to know where is this animal and basically eat it at that point, giving it sort of the full blast.

SIMON: Dr. Catania, how (laughter) do you work with an electric eel? I mean, that'd be like working with dynamite, or kryptonite, wouldn't it?

CATANIA: Yeah, carefully (laughter). If you're wearing gloves it's really not too much of a problem because once you insulate your hands, it's kind of like, you know, having an insulated power cord. You're really not going to get shocked.

SIMON: And what does happen if you step in the way of an electric eel?

CATANIA: Well, there's a number of historical accounts. I've been careful enough not to experience this, but people who have dropped one they were studying on them - which happened in 1800's - they're frozen-up and can't move while the eel is discharging. Same as a Taser would cause muscle contractions that would immobilize you.

SIMON: So proceed carefully when you know there are eels around, I guess?

CATANIA: I would say so, yeah.

SIMON: Professor Ken Catania, thanks so much for being with us.

CATANIA: It was a pleasure. Transcript provided by NPR, Copyright NPR.