A fish swims in the Amazon, amid murky water and overgrown vegetation. It is concealed, but it’s not safe. Suddenly, two rapid bursts of electricity course through the water, activating the neurons that control the fish’s muscles. It twitches, giving away its position, and dooming itself. Now, it gets zapped by a continuous volley of electric pulses. All its muscles contract and its body stiffens. It can’t escape; it can’t even move. Its attacker—an electric eel—moves in for the kill.

The electric eel can (in)famously create its own electricity. More than four-fifths of its two-metre-long body consists of special battery-like cells, which can collectively deliver a jolt of up to 600 volts. But the way the eel uses that ability is