Evolution and Taxonomy
– Electric eels are neotropical freshwater fish from South America in the family Gymnotidae.
– They have the ability to stun prey by generating electricity, delivering shocks at up to 860 volts.
– Their electrical capabilities were first studied in 1775 and contributed to the invention of the electric battery in 1800.
– Electric eels are not closely related to true eels (Anguilliformes) but belong to the electroreceptive knifefish order, Gymnotiformes.
– In 2019, electric eels were divided into three species: Electrophorus electricus, E. voltai, and E. varii.
– Carl Linnaeus originally described the electric eel as Gymnotus electricus in 1766.
– In 1864, Theodore Gill moved the electric eel to its own genus, Electrophorus.
– The name Electrophorus comes from the Greek words for amber (a substance that can hold static electricity) and carry, meaning electricity bearer.
– In 1872, Gill classified the electric eel into its own family, Electrophoridae.
– In 2019, C. David de Santana and colleagues divided Electrophorus electricus into three species based on DNA divergence, ecology, anatomy, and electrical ability.
Phylogeny and Ecology
– Electric eels form a clade of strongly electric fishes within the order Gymnotiformes.
– They are not closely related to true eels (Anguilliformes).
– The Electrophorus genus split from its sister taxon Gymnotus sometime in the Cretaceous.
– Most knifefishes are weakly electric and cannot deliver shocks.
– Phylogenetic relationships were analyzed using mitochondrial DNA sequencing in 2019.
– The three species of electric eels have non-overlapping distributions in northern South America.
– E. electricus is found in the Guiana Shield, E. voltai in the Brazilian shield, and E. varii in the lowlands.
– Their habitats range from streams to ponds, with large changes in water level between wet and dry seasons.
– Electric eels live on muddy river bottoms, prefer areas in deep shade, and can tolerate low oxygen levels.
– E. voltai mainly eats fish, while E. varii preys on armoured catfishes and cichlids.
Anatomy and Physiology
– Electric eels have long, stout bodies that are cylindrical at the front and flattened towards the tail.
– They can reach up to 2m in length and 20kg in weight.
– Electric eels have smooth, thick, brown-to-black skin with a yellow or red underbelly and no scales.
– They have over 100 precaudal vertebrae and an anal fin with over 400 bony rays.
– Electric eels breathe air using buccal pumping and can survive on land for some hours if their skin is wet enough.
– Lateral line pits contain electroreceptors and mechanoreceptors.
– Electroreceptors derived from lateral line organ in the head.
– Mechanosensory lateral line enables sensing of water movements.
– High frequency-sensitive tuberous receptors used for hunting.
– Electric eels have three pairs of electric organs: main, Hunters, and Sachs.
– Electric organs generate low voltage and high voltage discharges.
– Electrocytes in the organs are modified from muscle cells.
– Proteins actin and desmin present in electrocytes.
– Potassium channel proteins distributed differently among organs.
– Calmodulin and calcium regulate voltage-gated sodium channels.
Electric Eel Capabilities
– Electric eels can generate a discharge of at least 600 volts.
– Discharge is produced rapidly at a rate of 500 Hertz.
– High-voltage, high-frequency pulses enable electrolocation.
– Total electric current delivered during each pulse can reach 1 ampere.
– Stacking of electrocytes in series allows for high voltage production.
– Electric eels use electric organ discharge to stun prey.
– Nerve signal triggers discharge through acetylcholine release.
– Ion channels allow sodium to flow into electrocytes, reversing polarity.
– Discharge terminated by outflow of potassium ions.
– Electric eels can concentrate discharge to stun prey more effectively.
Interactions with Humans and Applications
– Early experiments on electric eels conducted in the 1760s.
– Electric eels and electric rays studied by John Walsh and John Hunter.
– Electric eels have been observed to leap from water to shock threats.
– Shocks from leaping electric eels can drive away animals as large as horses.
– Captive electric eels have lived for over 20 years.
– Contributions to scientific research, including electrophysiology and electrochemistry.
– Indigenous people using horses to hunt electric eels.
– Alexander von Humboldt witnessed horses being stunned and drowned by the eels’ shocks.
– Electric eel research contributing to the development of artificial electrocytes and their applications in medical implants and power sources for devices. Source: https://en.wikipedia.org/wiki/Electric_eel
The electric eels are a genus, Electrophorus, of neotropical freshwater fish from South America in the family Gymnotidae. They are known for their ability to stun their prey by generating electricity, delivering shocks at up to 860 volts. Their electrical capabilities were first studied in 1775, contributing to the invention in 1800 of the electric battery.
| Electric eel | |
|---|---|
 | |
| Electrophorus electricus specimen at the New England Aquarium | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Gymnotiformes |
| Family: | Gymnotidae |
| Genus: | Electrophorus T. N. Gill, 1864 |
| Type species | |
| Gymnotus electricus Linnaeus, 1766 | |
| Species | |
| |
| Synonyms | |
| |
Despite their name, electric eels are not closely related to the true eels (Anguilliformes) but are members of the electroreceptive knifefish order, Gymnotiformes. This order is more closely related to catfish. In 2019, electric eels were split into three species: for more than two centuries before that, the genus was believed to be monotypic, containing only Electrophorus electricus.
They are nocturnal, obligate air-breathing animals, with poor vision complemented by electrolocation; they mainly eat fish. Electric eels grow for as long as they live, adding more vertebrae to their spinal column. Males are larger than females. Some captive specimens have lived for over 20 years.
