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Electric eel

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Electric eels are a genus of neotropical freshwater fish found in South America. They belong to the family Gymnotidae and the subfamily Electrophorinae.

Lateral view of Electrophorus electricus
Lateral view of Electrophorus electricus

Despite their common name, they are not true eels from the order Anguilliformes. Instead, they are members of the knifefish order Gymnotiformes. This group is actually more closely related to catfish than to true eels. These fish are famous for their ability to generate powerful electrical shocks. They use this electricity to stun prey and navigate their dark environments.

Carte du nord de l'Amérique du sud avec répartition de spécimens de 3 espèces d'anguilles électriques electrophorus
Carte du nord de l'Amérique du sud avec répartition de spécimens de 3 espèces d'anguilles électriques electrophorus

To create electricity, the eel uses three specialized electric organs. These are arranged longitudinally along its body. They are called the main organ, Hunter's organ, and Sachs' organ.

Electric eel's electric organs
Electric eel's electric organs

These organs are made of modified muscle cells known as electrocytes. To produce a high-voltage shock, the eel stacks approximately 6,000 electrocytes in a series. This means they are lined up one after another in long columns. The main organ contains about 35 of these stacks in parallel on each side of the body. This arrangement allows the eel to reach very high voltages. Because freshwater has high electrical resistance, the eel must produce high voltage to deliver a strong shock.

Impedance matching in electric fishes
Impedance matching in electric fishes

There are three distinct species within the genus Electrophorus. For a long time, scientists believed the genus was monotypic, meaning it had only one species. However, research in 2019 divided the group into three species based on DNA and anatomy.

The first is Electrophorus electricus, which has a U-shaped head and a flattened skull. The second is Electrophorus voltai, which has an egg-shaped head. This species is the strongest bioelectricity generator in nature, capable of reaching 860 volts. The third is Electrophorus varii, which has a thicker skull and a more variable head shape. These species live in different parts of northern South America. E. electricus lives in the Guiana Shield, E. voltai lives in the Brazilian shield, and E. varii lives in the central lowlands.

Humans have been studying these fish for centuries. Carl Linnaeus first described the fish in 1766. He originally named it Gymnotus electricus after studying specimens from Surinam. In 1864, Theodore Gill moved the fish to its own genus, Electrophorus. This name comes from Greek words meaning "electricity bearer." In 1872, Gill also established the family Electrophoridae. The study of these fish has had a major impact on human technology. Research into their electrical capabilities in 1775 contributed to the invention of the electric battery in 1800.

Exodon paradoxus Castelnau
Exodon paradoxus Castelnau

Electric eels possess unique biological features that help them survive. They are nocturnal animals that live on muddy river bottoms or in swamps. They are obligate air-breathers, which means they must breathe air to survive. They use a process called buccal pumping to take in air. They hold the air in a buccal cavity lined with a frilled mucosa. This specialized tissue allows for gas exchange between the air and the blood. This ability lets them live in water that has very low oxygen levels.

Electrophorus electricus - squelette MNHN (cropped)
Electrophorus electricus - squelette MNHN (cropped)

Their bodies are also quite unique, containing as many as 300 vertebrae. This is much more than other knifefish, which may have only 51.

Because they have poor vision, electric eels rely on other senses to hunt. They use electrolocation to find prey in dark or murky water.

Electrophorus electricus showing lateral line pits
Electrophorus electricus showing lateral line pits

Tiny pits on their head and body contain electroreceptors. These receptors detect electrical signals from other living things. They also have a mechanosensory lateral line to sense water movements. To hear, they use a Weberian apparatus. This is a system of tiny bones that connects the inner ear to the swim bladder. These combined senses allow them to hunt fish and other animals effectively in total darkness.

These fish play a specific role in their ecosystem. E. voltai often hunts in packs to target schools of fish. They have been observed herding tetras and launching joint strikes.

Other species, like E. varii, prey on armored catfishes and cichlids. Their biological complexity connects to many fields of study. Their electrocytes provide insight into cell biology and protein functions. Their ability to generate electricity is a key example of extreme evolutionary adaptation. This makes the electric eel a vital subject for understanding how animals interact with their physical environment.

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🖼️ Images & Media (18)
File:Farm-Fresh lightning.png
Farm-Fresh lightning.png
File:Lightning Symbol.svg
Lightning Symbol.svg
File:Exodon paradoxus Castelnau.jpg
Exodon paradoxus Castelnau.jpg
File:Sternarchorhynchus oxyrhynchus.jpg
Sternarchorhynchus oxyrhynchus.jpg
File:Hypopomidae Steatogenys elgans (cropped).jpg
Hypopomidae Steatogenys elgans (cropped).jpg
File:Rhamphichthys marmoratus.jpg
Rhamphichthys marmoratus.jpg
File:Gymnotus sp.jpg
Gymnotus sp.jpg
File:Lateral view of Electrophorus electricus.png
Lateral view of Electrophorus electricus.png
File:Sternopygidae Eigenmannia sp (white background).jpg
Sternopygidae Eigenmannia sp (white...
File:FMIB 51852 Electric Catfish, Torpedo electricus (Gmelin) Congo River.jpeg
FMIB 51852 Electric Catfish, Torpedo...
File:Anguilles électriques 3 espèces Nature 10 sept 2019 C. David de Santana et al.png
Anguilles électriques 3 espèces Nature 10...
File:Carte du nord de l'Amérique du sud avec répartition de spécimens de 3 espèces d'anguilles électriques electrophorus.png
Carte du nord de l'Amérique du sud avec...

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