Electric organ (fish)

Electric organs are derived from modified muscle or in some cases nerve tissue, called electrocytes, and have evolved at least six times among the elasmobranchs and teleosts.

[9][10] Since the 20th century, electric organs have received extensive study, for example, in Hans Lissmann's pioneering 1951 paper on Gymnarchus[11] and his review of their function and evolution in 1958.

[14] However, in two marine groups, the stargazers and the torpedo rays, the electric organs are oriented along the dorso-ventral (up-down) axis.

[13] The stack of electrocytes has long been compared to a voltaic pile, and may even have inspired the 1800 invention of the battery, since the analogy was already noted by Alessandro Volta.

[18][19][20][21] Notably, they have convergently evolved in the 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 which produces electric discharges.

[24] Comparative transcriptomics of the Mormyroidea, Siluriformes, and Gymnotiformes lineages conducted by Liu (2019) concluded that although there is no parallel evolution of entire transcriptomes of electric organs, there are a significant number of genes that exhibit parallel gene expression changes from muscle function to electric organ function at the level of pathways.

Electric organ discharges (EODs) need to vary with time for electrolocation, whether with pulses, as in the Mormyridae, or with waves, as in the Torpediniformes and Gymnarchus, the African knifefish.

[33] In the book, women develop the ability to release electrical jolts from their fingers, powerful enough to stun or kill.

An electric ray ( Torpediniformes ) showing location of paired electric organs in the head, and electrocytes stacked within it
The electric eel 's three electric organs – the main organ, Sachs 's organ, and Hunter 's organ – occupy much of its body, as was discovered in the 1770s . They can discharge weakly for electrolocation , as in other gymnotids , and strongly to stun prey.
Electric eel anatomy: first detail shows electric organs, made of stacks of electrocytes. Second detail shows an individual cell with ion channels and pumps through the cell membrane ; A nerve cell's terminal buttons are releasing neurotransmitters to trigger electrical activity. Final detail shows coiled protein chains of an ion channel.
Electrocytes evolved from an existing excitable tissue, skeletal muscle . [ 13 ] Electrocytes are assembled into stacks to create larger voltages (and into multiple stacks to create larger currents , not shown). Electric fish may have diphasic discharges (as shown), or discharges of other kinds.