Knollenorgan
A Knollenorgan is an electroreceptor in the skin of weakly electric fish of the family Mormyridae (Elephantfish) from Africa.
The structure was first described by Viktor Franz (1921), a German anatomist unaware of its function.
Knollenorgans contain modified epithelial cells that act as sensory transducers for electric fields.
The sense organ is surrounded by a basement membrane which separates corium from epidermis.
[2][3][4][5] Knollenorgans lack the jelly-filled canal leading from sensory receptor cells to the external environment characteristic of the ampullae of Lorenzini found in sharks and other basal groups of fishes.
The organ is embedded in the skin of mormyrid fishes, which actively electrolocate by generating brief electrical pulses with their electric organ . The returns from the pulses, distorted by any nearby objects such as prey, are detected by the knollenorgans distributed around the fish's body.