The Electric Organ

Image courtesy of Masashi Kawasaki

This webpage was created by Christopher Castillo '07 as an assignment for an undergraduate course Biology 312 (Animal Physiology) at Davidson College.

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The Electric Organ

All electrical fish produce electrical discharges from an organ located in their tail. This organ is called the electric organ. Electric organs consist of columns of electrocytes which are stimulated by electric signals from the brain. These cells are surrounded by connective tissue, which channels the flow of current along the axis of the organ, out into the water, and back into the other end of the electric organ ( Hopkins, 1974).

The current that is created and is released out into the water is called the electric organ discharge, or EOD. EODs vary in voltage between strongly electric fish and weakly electric fish. In strongly electric fish, there voltage can range from 150-600 volts, while the voltage of weakly electric fish is typically less than one volt (Nelson, 2005).

There are two different types of EODs, pulse type and wave type. In some species of electric fish, the EOD waveform consists of short pulses that are separated by long gaps. These are known as pulse type EODs. In other species, the wave form is more frequent (Nelson, 2005)(Kawasaki, 2005).

Image courtesy of Masashi Kawasaki

 

Electric fish have sensory neurons throughout their bodies which can detect changes in the electric field caused by foreign objects. These specialized receptors are called electroreceptors (Shua, Kashimori,Kambara, 1998 ).

There are two classes of electroreceptors found in electric fish, ampullay and tuberous receptors. Ampullay receptors are classified as “low-pass filters”, because they can only detect frequencies below 20Hz. Tuberous receptors are considered “high-pass filters”, because they are sensitive to frequencies between thirty Hz to over 200 Hz (Shua, 1998).