Electric organ (biology)

In biology, the electric organ is an organ common to all electric fish used for the purposes of creating an electric field. The electric organ is derived from modified nerve or muscle tissue. The electric discharge from this organ is used for navigation, communication, defense and also sometimes for the incapacitation of prey.

In the 1770s the electric organs of the torpedo and electric eel were the subject of Royal Society papers by Hunter, Walsh and Williamson. They appear to have influenced the thinking of Luigi Galvani and Alessandro Volta - the founders of electrophysiology and electrochemistry.

In the 19th century, Charles Darwin discussed the electric organ in his Origin of Species as a likely example of convergent evolution: "But if the electric organs had been inherited from one ancient progenitor thus provided, we might have expected that all electric fishes would have been specially related to each other…I am inclined to believe that in nearly the same way as two men have sometimes independently hit on the very same invention, so natural selection, working for the good of each being and taking advantage of analogous variations, has sometimes modified in very nearly the same manner two parts in two organic beings".

Since the 20th Century, electric organs have received extensive study, for example Lissmann's 1951 paper and his review of their function and evolution in 1958.

Electric organs seem to have evolved at least six times in various teleost and elasmobranch fish.

Electrocytes, electroplaques or electroplaxes are cells used by electric eels, rays, and other fish for electrogenesis. They are flat disk-like cells. Electric eels have several thousand of these cells stacked, each producing 0.15 V. The cells function by pumping positive sodium and potassium ions out of the cell via transport proteins powered by adenosine triphosphate (ATP). Postsynaptically, electrocytes work much like muscle cells. They have nicotinic acetylcholine receptors.

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