Original photo by tristan tan/ Shutterstock

Eating eel is common around the world, especially in Japan, where it’s often found in sushi. But whether it’s freshwater or marine eel, the animal is always served cooked, because toxins found in its blood can cause extreme muscle cramping if consumed by humans. This cramping can affect your body’s most important muscle — the heart — which is why eating raw eel can be fatal. Luckily, when eels are cooked, those deadly toxins break down and the animal becomes safe to consume. This is good news for chefs, since eel provides a rich taste similar to squid but with a softer texture. 

All animals contain some form of blood.

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Although blood is a common trait among most animals, it’s not necessarily a prerequisite. Flatworms, nematodes, sea anemones, and jellyfish don’t have blood, and animals like starfish instead use seawater to transfer vital nutrients throughout their bodies.

Although eel blood is a particularly dangerous fluid, that didn’t stop French physiologist Charles Richet from experimenting with the stuff in the early 1900s. Inspired by fellow countryman Louis Pasteur and his discoveries in immunology, Richet experimented with a toxin found in eel blood serum and discovered the hypersensitivity reaction known as anaphylaxis. “Phylaxis, a word seldom used, stands in the Greek for protection,” Richet said during a lecture after receiving the Nobel Prize for his work in 1913. “Anaphylaxis will thus stand for the opposite.” So while the everyday eel may be a slippery, slimy, and all-around unappealing animal to some, it holds a distinguished position in the annals of both scientific history and culinary delight.

Numbers Don't Lie

Numbers Don't Lie

Size (in centimeters) of Snyder’s moray eel, the smallest eel in the world
11.5
Release year of the animated film “The Little Mermaid,” featuring villainous eels Flotsam and Jetsam
1989
Distance (in miles) of capillaries, veins, and arteries in the human body if laid end-to-end
60,000
Estimated number of eel species
800

American eels are ______, which means they’re freshwater fish that spawn in salt water.

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American eels are catadromous, which means they’re freshwater fish that spawn in salt water.

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Electric eels inspired the world’s first battery.

From smartphones to electric cars, today’s world is powered by batteries, and it’s all thanks to electric fish and one stubbornly curious Italian chemist. Near the end of the 18th century, Alessandro Volta wanted to see if he could artificially recreate the electric organs found in electric eels (which are technically not eels) and rays. These organs look like stacked cells that closely resemble a roll of coins, and are used to stun potential prey with up to 1,000 volts. Volta tried to mimic this structure by stacking sheets of various materials to see if he could similarly produce electricity. All of his experiments failed, until he stumbled across a winning combination: alternating copper and zinc disks separated by paper soaked in salt water. While Volta originally named the world’s first battery an “artificial electric organ,” he actually discovered a wholly separate mechanism for creating electricity. Instead, fishes like eels use a process similar to how human nerves transmit electricity, but on a much larger scale. Yet because of Volta’s happy electrochemical accident, you can read these words on your favorite battery-powered, eel-inspired device.

Darren Orf
Writer

Darren Orf lives in Portland, has a cat, and writes about all things science and climate. You can find his previous work at Popular Mechanics, Inverse, Gizmodo, and Paste, among others.