Electric eels are a type of knifefish, not true eels, found primarily in the Amazon and Orinoco basins of South America. These fish possess a unique adaptation: the ability to generate powerful electrical discharges. This capability allows them to navigate, hunt, and defend themselves. Their specialized organs enable them to produce electricity.
The Science Behind Their Shock
Electric eels generate electricity using specialized cells called electrocytes, which are modified muscle cells. These disc-shaped electrocytes are stacked in columns, much like batteries, within three distinct electric organs. The main organ and Hunter’s organ are responsible for strong discharges, while the Sach’s organ produces weaker impulses. Each electrocyte creates a small voltage by controlling the flow of ions across its membrane.
When the eel produces a shock, its brain sends a signal to these electrocytes. This triggers a rapid influx of positively charged sodium ions into the cells, momentarily reversing their electrical polarity. Subsequently, potassium ions flow out, terminating the discharge. The synchronized discharge of thousands of these electrocytes, arranged in series, collectively generates a substantial electrical current, creating a significant potential difference.
Why Electric Eels Electrocute
Electric eels utilize their electrical capabilities for various purposes, adapting their discharge strength to suit different situations. They employ high-voltage shocks to stun or incapacitate prey, remotely controlling their muscles to prevent escape or to force hidden prey to twitch and reveal their location. When dealing with struggling prey, eels can curl their bodies to concentrate the electrical field, delivering a more focused and powerful shock.
For defense, electric eels deploy strong electrical bursts to deter predators. They can even leap partially out of the water to directly electrify a threat, delivering a more potent shock than they could while fully submerged. Electric eels also use weaker, low-voltage pulses for navigation and sensing their environment, especially in murky waters where visibility is limited. These pulses create an electric field around them, and the eels detect distortions in this field caused by nearby objects or other animals, effectively “seeing” with electricity. They also use these low-voltage discharges for communication.
The Impact of an Electric Eel’s Discharge
The electrical discharge from an electric eel can be powerful, with some species capable of generating up to 860 volts and currents approaching 1 ampere. Even juveniles can produce significant shocks, with those measuring 7-10 cm capable of generating 100 volts. This electricity is enough to stun or kill smaller animals.
For humans, a single shock from an electric eel is rarely fatal, but it can be intensely painful and cause involuntary muscle contractions. The jolt can lead to temporary paralysis, and in water, this incapacitation poses a risk of drowning. Multiple shocks or prolonged exposure can be more dangerous, potentially causing respiratory distress or heart failure, particularly in individuals with pre-existing heart conditions. Historical accounts describe electric eel shocks being powerful enough to knock down horses.