UNDER THE SEA

 Hello ladies and gents this is the Viking telling you that today we are talking about 

ELECTRIC EEL

The electric eel (Electrophorus electricus, other species proposed) is a South American electric fish. Until 2019, it was classified as the only species in its genus. Despite the name, it is not an eel, but rather a knifefish. It is considered as a fresh water teleost which contains an electrogenic tissue that produces electric discharges.

The electric eel 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 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 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 (Anguilliformes) but is a member of the neotropical knifefish order (Gymnotiformes), which is more closely related to the catfish.

The electric eel has three pairs of abdominal organs that produce electricity: the main organ, Hunter's organ, and Sachs' organ. These organs make up four fifths of its body, and give the electric eel the ability to generate two types of electric organ discharges: low voltage and high voltage. 

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. The three electrical organs are developed from muscle and exhibit several biochemical properties and morphological features of the muscle sarcolemma; they are found symmetrically along both sides of the eel.

When the eel finds its prey, the brain sends a signal through the nervous system to the electrocytes. This opens the ion channels, allowing sodium to flow through, reversing the polarity momentarily. By causing a sudden difference in electric potential, it generates an electric current in a manner similar to a battery, in which stacked plates each produce an electric potential difference. Electric eels are also capable of controlling their prey's nervous systems with their electrical abilities; by controlling their victim's nervous system and muscles via electrical pulses, they can keep prey from escaping or force it to move so they can locate its position.

Sachs' organ is associated with electrolocation. Inside the organ are many muscle-like cells, called electrocytes. Each cell can only produce 0.15 V, though the organ can transmit a signal of nearly 10 V overall in amplitude at around 25 Hz in frequency. These signals are emitted by the main organ; Hunter's organ can emit signals at rates of several hundred hertz.

There are several physiological differences among the three electric organs, which allow them to have very different functions. The main electrical organ and the strong-voltage section of Hunter's organ are rich in calmodulin, a protein that is involved in high-voltage production.

The electric eel is unique among the Gymnotiformes in having large electric organs that can produce potentially lethal discharges that allow them to stun prey. Larger voltages have been reported, but the typical output is sufficient to stun or deter virtually any animal. 

Juveniles produce smaller voltages (about 100 V). They can vary the intensity of the electric discharge, using lower discharges for hunting and higher intensities for stunning prey or defending themselves. They can also concentrate the discharge by curling up and making contact at two points along its body. When agitated, they can produce these intermittent electric shocks over at least an hour without tiring.

The electric eel also possesses high frequency–sensitive tuberous receptors, which are distributed in patches over its body. This feature is apparently useful for hunting other Gymnotiformes.

Electric eels have been used as a model in the study of bioelectrogenesis. The species is of some interest to researchers, who make use of its acetylcholinesterase and adenosine triphosphate.

Michael Faraday extensively tested the electrical properties of an electric eel, imported from Suriname. For a span of four months, Faraday carefully and humanely measured the electrical impulses produced by the animal by pressing shaped copper paddles and saddles against the specimen. Through this method, Faraday determined and quantified the direction and magnitude of electric current, and proved the animal's impulses were in fact electrical by observing sparks and deflections on a galvanometer.

Bionics

Researchers at Yale University and the National Institute of Standards and Technology argue artificial cells could be built that not only replicate the electrical behavior of electric eel cells, but also improve on them. Artificial versions of the eel's electricity-generating cells could be developed as a power source for medical implants and other microscopic devices.

And as always have a chilled day from the Viking