What are Electric Eels?
You might have seen electric eels in aquariums. They do not look fancy or interesting with their long, dark green or grayish cylindrical bodies and flattened heads. They can grow up to 2.5m and weigh up to 20kg.
Despite their name, electric eels are not eels. They’re scientifically closer to carp and catfish. Although human deaths from these eels are extremely rare, the electric eels are ranked in one of the most dangerous fish in the world. They are a part of the electric fish family that has special organs that produce electric pulses.
How do they produce electricity?
Electric eels have three electric organs: the main organ, Hunter’s organ, and Sach’s organ. The main organ and Hunter’s organ generates high-voltage pulses that stun prey and warn predators. On the other hand, Sach’s organ produces low-voltage pulses that allow eels to communicate and navigate in the murky waters.
The fish’s brain sends a signal through its nervous system to the electric organ or thousands of disc-shaped organ cells called electrocytes. These electrocytes pump out sodium and potassium ions to maintain a positive charge on the outside and negative charge on the inside. But when the signal arrives at the electrocytes, a path of low electrical resistance develops between one side of the cell. The ion gates open and allow potassium ions outside the cell to rush inward, which causes some of the potassium ions inside the cell to exit to the outside to maintain the cell’s equilibrium. With this process, about 150 millivolts of electricity are released from the cell. Since the stacks of electrocytes act like thousands of batteries in series, the electric eel can release up to 600 volts, which is five times the voltage of a U.S. wall socket.
▲ Electricity Producing Organs of an Electric Eel [7]
▲ Sodium(Na) and Potassium(K) Moving in and Out of a Cell to Create Voltage
How do they hunt?
The electric eel uses its signals to communicate and navigate, but it uses the strongest electric discharges for hunting. In murky waters, prey can be difficult to find. They developed motion-sensitive hairs along its body (the lateral line system) that detect the change in pressure of the surrounding water.
When the eel suspects a prey nearby, it emits two rapid electric pulses, called a doublet. First, it sends a strong pulse that stimulates the prey’s muscles, causing it to twitch involuntarily and generate waves that reveal its hiding place. Next, the electric eel releases a series of high-voltage pulses which paralyze its prey and allows the electric eel to swallow its meal alive.
Why don't they electrocute themselves?
Disclaimer: No one knows why electric eels don’t shock themselves. However, there are a few speculations. Some think that the eels’ body size may be the key. Since electric eels can grow up to 2.5m, the charge it deliversーup to 600 voltsーwould cause much less damage to the eel itself, compared to its victim. Some think that special proteins shield the electric organs to protect themselves or that the current passes out of their bodies too quickly to keep them unharmed. This mystery is yet to be solved.
[1]The Editors of Encyclopaedia Britannica. “Electric Eel.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 12 Feb. 2020, www.britannica.com/animal/Electrophorus-fish-genus.
[2]Electric Eel. 21 Sept. 2018, www.nationalgeographic.com/animals/fish/e/electric-eel/.
[3]“Electric Eel.” Smithsonian’s National Zoo, 27 June 2018, nationalzoo.si.edu/animals/electric-eel.
[4]“How Do Electric Eels Generate a Voltage and Why Do They Not Get Shocked in the Process?” Scientific American, Scientific American, 5 Dec. 2005, www.scientificamerican.com/article/how-do-electric-eels-gene/.
[5]Kwok, Roberta. “The Shocking Electric Eel!” Science News for Students, 3 Dec. 2019, www.sciencenewsforstudents.org/article/shocking-electric-eel.
[6]Nelsen, Eleanor. “How Do Fish Make Electricity? – Eleanor Nelsen.” TED, TED-Ed, ed.ted.com/lessons/how-do-fish-make-electricity-eleanor-nelsen.
[7] Yusuf Salama. 2020. “How Do Electric Fish Produce Electricity?” ScienceABC. https://www.scienceabc.com/nature/animals/how-do-electric-fish-produce-electricity.html. 08/26/20.
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