Research history and notable studies
– Detailed descriptions of electric shocks from electric catfish were recorded in ancient Egypt.
– John Walsh, Hugh Williamson, and John Hunter studied the electric organs of the torpedo ray and electric eel in the 1770s.
– Luigi Galvani and Alessandro Volta were influenced by the research on electric organs.
– Charles Darwin discussed the electric organs of electric eels and torpedo rays in his book ‘On the Origin of Species’ as an example of convergent evolution.
– Carl Sachs studied the fish and discovered Sachs organ in 1877.
– Hans Lissmann conducted pioneering studies on electroreception and electrogenesis in Gymnarchus niloticus in 1951.
– Torpedo californica electrocytes were used in the first sequencing of the acetylcholine receptor in 1982.
– Electrophorus electrocytes were used in the first sequencing of the voltage-gated sodium channel in 1984.
– Electric organs have received extensive study since the 20th century.
– Electric organs have provided valuable insights into bioelectricity and the evolution of electric fish.
Anatomy
– Electric organs in most fish are oriented along the length of the body, typically in the tail and within the musculature.
– In stargazers and torpedo rays, the electric organs are oriented along the dorso-ventral axis.
– The electric catfish has its organs located just below the skin, encasing most of the body.
– The elephantnose fish has the electric organ in its tail.
– Skates have their electric organ in the tail.
– Electric organs are composed of specialized cells called electrocytes, electroplaques, or electroplaxes.
– Electric eels have stacks of thousands of cells, each producing 0.15 V.
– Electrocytes pump sodium and potassium ions across their cell membranes, consuming ATP in the process.
– Electrocytes depolarize with an inflow of sodium ions and repolarize with an outflow of potassium ions.
– The stack of electrocytes has been compared to a voltaic pile and may have inspired the invention of the battery.
Evolution
– Electric organs have evolved at least six times in various teleost and elasmobranch fish.
– Convergent evolution of electric organs has been observed in African Mormyridae and South American Gymnotidae groups of electric fish.
– A whole-genome duplication event in the teleost lineage allowed for the neofunctionalization of the voltage-gated sodium channel gene Scn4aa.
– Comparative transcriptomics studies have shown parallel gene expression changes from muscle function to electric organ function.
– Electric organs are derived from skeletal muscle, except in Apteronotus where they are derived from neural tissue.
Electric organ discharge
– Electric organ discharges (EODs) vary with time for electrolocation, either with pulses or waves.
– Electric fish use EODs for communication, while strongly electric species use them for hunting or defense.
– Electric signals are often simple and stereotyped, remaining the same on every occasion.
– EODs can be diphasic or of other kinds, depending on the species.
– Electric fish assemble electrocytes into stacks to create larger voltages and currents.
Miscellaneous
– Electric organs have provided valuable insights into bioelectricity and the evolution of electric fish. Source: https://en.wikipedia.org/wiki/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.
