ELECTRIC FISHES
 | ELECTRIC FISHES STRONGLY ELECTRIC SPECIES: marine electric rays, freshwater African catfish, freshwater electric eel WEAKLY ELECTRIC SPECIES: freshwater South American knifefish and African elephant fish ELECTRICALLY SENSITIVE SPECIES: Sharks, rays, skates and catfish |
Electrical energy is everywhere in nature, from sky splitting lightning to the minuscule currents that flow through nerve cells due to sodium or potassium ions passing in and out of the cell as they send signals throughout the body. Muscle contraction is also produced by this process, and also has electrical currents associated with it.
All organisms produce microelectrical fields that are generated by neuromuscular activity and "leak" out of the body. However, hundreds of species of fish do more, putting electricity to work by generating, storing and discharging electrical currents, either as massive blasts or using them to maintain a steady electrical field around the body.
Scientists sort electric fishes into three categories. Strongly electric fish like the marine electric rays we were catching or the African electric catfish and South American electric eel, deliver severe discharges to stun their prey and defend themselves. Powerful enough to stun or kill a human, these species that contain thunderbolts in their bodies have been known since the dawn of human history.
In recent years, scientists have also discovered a second catogory, the hundreds of species of weakly electric fishes in the Amazon and in fresh water streams in Africa. They maintain tiny fields of only a few millivolts to a volt around their bodies and use them for communication, navigation, and defending territory.
And finally all sharks, rays and catfish, although they do not emit a field, have electrical receptors, tiny sensory structures called Ampullae of Lorenzini, which enable them to detect the minuscule amounts of electricity that "leak" out of other organisms. On the electric rays, they appeared as tiny black dots on the underside of their white disks.
GULF SPECIMEN MARINE LAB • PO BOX 237 • PANACEA, FL 32346 USA • (850) 984-5297 • FAX (850) 984-5233
