Electric eel

Appearance

The electric eel has an elongated, cylindrical body, typically growing to about 2 m in length, and 20 kg in weight, making them the largest species of the Gymnotiformes. Their coloration is dark gray-brown on the back and yellow or orange on the belly. Mature females have a darker color on the abdomen. They have no scales. The mouth is square, and positioned at the end of the snout. The anal fin extends the length of the body to the tip of the tail.

As in other ostariophysan fishes, the swim bladder has two chambers. The anterior chamber is connected to the inner ear by a series of small bones derived from neck vertebrae called the Weberian apparatus, which greatly enhances its hearing capability. The posterior chamber extends along the whole length of the body and maintains the fish's buoyancy. "E. electricus" has a well-developed sense of hearing. This fish has a vascularized respiratory system with gas exchange occurring through epithelial tissue in its buccal cavity. As obligate air-breathers, electric eels must rise to the surface every ten minutes or so to inhale before returning to the bottom. Nearly eighty percent of the oxygen used by the fish is obtained in this way.

Despite its name, the electric eel is not closely related to the true eels but is a member of the neotropical knifefish order, which is more closely related to the catfish.

Habitat

Electric eels inhabit fresh waters of the Amazon and Orinoco River basins in South America, in floodplains, swamps, creeks, small rivers, and coastal plains. They often live on muddy bottoms in calm or stagnant waters.Electric eels feed on invertebrates, although adult eels may also consume fish and small mammals, such as rats. First-born hatchlings eat other eggs and embryos from later clutches. The juveniles eat invertebrates, such as shrimp and crabs.

Reproduction

The electric eel is known for its unusual breeding behavior. In the dry season, a male eel makes a nest from his saliva into which the female lays her eggs. As many as 3,000 young hatch from the eggs in one nest. Males grow to be larger than females by about 35 cm.

Food

Electric eels feed on invertebrates, although adult eels may also consume fish and small mammals, such as rats. First-born hatchlings eat other eggs and embryos from later clutches. The juveniles eat invertebrates, such as shrimp and crabs.

Evolution

The species is so unusual that it has been reclassified several times. When originally described by Carl Linnaeus in 1766, he used the name "Gymnotus electricus", placing it in the same genus as "Gymnotus carapo" which he had described several years earlier. It was only about a century later, in 1864, that the electric eel was moved to its own genus "Electrophorus" by Theodore Gill.

Later the electric eel was considered sufficiently distinct to have its own family, Electrophoridae, but it has since been merged back into the family Gymnotidae, alongside "Gymnotus".