Learning From Electric Fish

Weakly electric fish knifefish produce and detect electric fields, and they use these electric fields in social communication and to detect objects. Johns Hopkins University neuroethologist Eric Fortune has traveled to Ecuador to study the fish in their native habitat. Back at Johns Hopkins University, research collaborators use Fortune's field data to help with their observations and experiments in the lab. With support from the National Science Foundation, they are studying the knifefish to learn more about how the brains of animals work to control their behavior. Engineers at Northwestern University are developing a highly agile robot based on the electric fish that could some day monitor the health of coral reefs or navigate the murky waters of an oil spill.

Transcript

00:00:10 MILES O'BRIEN: Like a taser, an electric eel can generate enough current to stun its prey. These so-called weakly electric fish generate electricity, too, but not enough to do any harm. With the proper equipment you can even hear an electric hum. ERIC FORTUNE: These fish are unique in that they produce and detect electric fields. And they use these electric fields in social communication, and to detect objects. MILES O'BRIEN: With support from the National Science Foundation, neuroethologist, Eric Fortune, traveled to Ecuador to study the weakly electric knife fish in its native habitat. Back at Johns Hopkins University, his research partner, mechanical engineer, Noah Cowan, and others, are studying the knife fish in the lab. He says it uses its electric field as a sixth sense- not only to communicate, but to navigate its surroundings, and to find its next meal.

00:01:05 NOAH COWAN: There's a small organ in the tail of the weakly electric fish that generates an electric field. And then that electric field envelops the entire animal. MILES O'BRIEN: When an object passes through the field, the fish has receptors on its skin to detect it. NOAH COWAN: There's little voltage sensors all over the surface of the skin. And as an object comes by, the voltage changes, and it says, Aha! Lunch. Or it says, I'm gonna be lunch, and it runs away. MILES O'BRIEN: Each fish generates its own unique frequency, which can change when other knife fish are near. NOAH COWAN: When the two fish come by, their two pitches begin to interact much like two singer's pitches would interact. And what we've done is really begin to explore how multiple fish, more than two, interact. SARAH STAMPER: The fish will swim both forwards and backwards using his ribbon fin. MILES O'BRIEN: And when the lights go out and it's hard for the fish to see, they seem to lean even more

00:01:57 on their electro-sense to navigate. NOAH COWAN: When the lights are on, you move the tube and they're just tracking along like this. When you turn off the lights, they start sort of- almost like they're feeling around with their electro-sense. They start moving around back and forth. MILES O'BRIEN: The goal is to understand how the brain of this unique animal controls its behavior. And engineers at Northwestern University are developing a highly agile robot that may one day use a similar sixth sense to monitor the health of coral reefs or navigate the dark, murky waters of an oil spill. For Science Nation, I'm Miles O'Brien.