How the electric eel (Electrophorus electricus) produces electricity to stun its prey

We have all learned to be afraid of the electric eel (Electrophorus electricus) when we were growing up, but despite its name, this fish is not an eel at all. We have over 800 species of eel in the world, and these all belong to the order Anguilliformes, while the electric “eel” belongs to the order Gymnotiformes, more commonly known as knifefish.

Anyway, this post is not about discussing the naming and taxonomy of eels, but about the electric eels’ ability to produce electricity to stun its prey. I’m just going to include a really short description of the fish, and then we dive into the electricity production! Stay with me, because I promise that this is really interesting!

Image by Steven G. Johnson, posted with the Creative Commons Attribution-Share Alike 3.0 Unported license*.

The electric eel is found in rivers in the tropical rainforest Amazonas in South America, where you tend to find them in areas with very muddy water. They can reach 2+ meters in length, and weigh over 20kg, so this is not a small fish by any means! They have extremely poor eyesight, but can use electricity to locate their prey before using the same tactic to stun them. They feed on whatever they can fit into their mouths, including both amphibians, fish, small mammals and pretty much anything.

How the electric eel produces electricity

The electric eels has three different abdominal organs that produce electricity; the main organ, the Hunter’s organ (used to stun prey), and the Sach’s organ (used to locate prey). In total these organs constitute about 4/5 of its entire body! Inside these organs we find electrocytes, cells that is specialized to store and discharge energy. Each cell can produce around 0,15V each, and the electric eel has up to six thousands of these! Individually each cell is harmless to most living things, but stacked together they become deadly for a lot of smaller animals.

The cells function a lot like a muscle cell, and gets its energy from sodium and potassium pumps powered by ATP. The chemical energy is converted to electric energy, and discharged by the fish. A full discharge of all the cells can create a shock with 860 volts, which is roughly 50 times the shocking power of a car battery! The ampere is luckily only at 1A, giving us a total of 860 watts for two milliseconds. This amount of electricity is comparable to a stun gun, so it can be really hurtful for humans. The shock is so short that it is generally not considered deadly to humans, so you don’t really have to worry about being killed by them. The big exception is of course if you are swimming, and the discharge might actually lead to drowning if you get stunned.

Keeping electric eels in your aquarium

I used to be very active in the aquarium scene some years ago, and met a few people that kept electric eels in their aquariums! I don’t really have a lot of information about it, except the fact that these were kept in huge tanks (3-5 000 liters), and mostly kept alone or fish other large fish. You would need to discharge the fish or wear special equipment before cleaning the tank, so this fish should only be kept by people who are extremely interested in it!

I wish I would have had the opportunity to see one of the tanks, but sadly this has not happened yet.

Other fish can also produce electricity

There are many fish that have the ability to discharge electricity, and these all have the specialized electrocyte cells. Most fish uses this ability to discharge electricity to locate objects near them, a feature known as electrolocation. This is a unique niche that some fish use, and can sometimes be found in fish that live in murky waters, in caves (with very little light) or fish that are active at night.

Read more

If you are interested to dive deeper into this area of biology, then check out this post at Ask a Naturalist.com. This is a great introduction that also has sources to the original research. I used this as my primary resource, so check it out!

Thanks for reading!