Electric organ (fish)

In biology, the electric organ is an organ that an electric fish uses to create an electric field. Electric organs are derived from modified muscle or in some cases nerve tissue, and have evolved at least six times among the elasmobranchs and teleosts. These fish use their electric discharges for navigation, communication, mating, defence, and in strongly electric fish also for the incapacitation of prey. The electric organs of two strongly electric fish, the torpedo ray and the electric eel were first studied in the 1770s by John Walsh, Hugh Williamson, and John Hunter. Charles Darwin used them as an instance of convergent evolution in his 1859 On the Origin of Species. Modern study began with Hans Lissmann's 1951 study of electroreception and electrogenesis in Gymnarchus niloticus. Detailed descriptions of the powerful shocks that the electric catfish could give were written in ancient Egypt. In the 1770s the electric organs of the torpedo ray and electric eel were the subject of Royal Society papers by John Walsh, Hugh Williamson, and John Hunter, who discovered what is now called Hunter's organ. These 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 organs of the electric eel and the torpedo ray in his 1859 book On the 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". In 1877, Carl Sachs studied the fish, discovering what is now called Sachs' organ.