Standby: Electric Fish Turn Down Charge for Energy Efficiency

Fish that use electric fields to sense their environments dim their signals to save energy during the day when they are resting.

Sternopygus macrurus, a South American river fish, is a natural practitioner of energy efficiency. It can reshape the charged-molecule channels in its electricity-producing cells to tone down its electrical signature within a matter of minutes.

“This is a really expensive signal to produce. The fish is using up a lot of its energy budget,” said neurobiologist Michael Markham at the University of Texas at Austin, lead author of a paper in PLoS Biology on the fish. “These animals are saving energy by reducing the strength of the signal when they are not active.”

Thousands of fish and other oceanic creatures use electrical fields to help them perceive their environments. The most famous is the electric eel, which a colleague of Markham’s termed “a frog with a cattle prod attached,” but most animals use the electrical signals in more subtle ways.

The fish’s standard electrical signal runs at 100 hertz; if you turn the electrical signal into sound, it sounds like a hum high whine. In laboratory experiments, the fish can detect tiny bugs half a centimeter wide and easily navigate obstacles by detecting the changes the objects cause in the electrical field.