Why do Electric Fish Swim Backwards?
This is not a trick question like the one about the chicken crossing the road. To understand the answer to the electric fish puzzle, we must restrict the discussion to those fish with active electric sensing systems. This group includes electric eels, South American knife fish, and African elephant snout fish. All of these have evolved, in a remarkable instance of parallel evolution, the capability of generating pulses of electricity. These pulses (up to 1,000 per second) radiate through the surrounding water. Prey and other nearby objects distort these oscillating electric fields. Electroreceptors on the fish and a sophisticated data processing system convert the field distortions into an “image” of the surroundings. Click here to read more.
