[5] In September 2019, David de Santana et al. suggested the division of the genus into three species based on DNA divergence, ecology and habitat, anatomy and physiology, and electrical ability: E. electricus, E. voltai sp.

[2] E. electricus has an elongated, cylindrical body, typically growing to about 2 m (6 ft 7 in) in length, and 20 kg (44 lb) in weight, making them the largest of the Gymnotiformes.

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.

E. electricus has a vascularized respiratory system with gas exchange occurring through epithelial tissue in its buccal cavity.

[7] As obligate air-breathers, E. electricus must rise to the surface every ten minutes or so to inhale before returning to the bottom.

These organs are made of electrocytes, lined up so a current of ions can flow through them and stacked so each one adds to a potential difference.

This opens the ion channels, allowing sodium to flow through, reversing the polarity momentarily.

High voltages are used to detect prey and, separately, stun them, at which point the electric eel applies a suction-feeding bite.

[14] Additionally, the three organs have varying amounts of Na+/K+-ATPase, which is a Na+/K+ ion pump that is crucial in the formation of voltage.

[citation needed] E. electricus also possesses high frequency–sensitive tuberous receptors, which are distributed in patches over its body.

[20] E. electricus feeds on invertebrates, although adult eels may also consume fish and small mammals, such as rats.

In the dry season, a male eel makes a nest from his saliva into which the female lays her eggs.