Animations & Cartoons

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About electric fishes

Animations created by Diana Marques, under my supervision, to the electric fish exhibit at the National Zoological Park
What are South American Electric Fishes? 
They are a group of 250+ species of freshwater fishes of the order Gymnotiformes that can generate their own electric field using at least one electric organ (orange line along the fish body in that Animations 1 & 2).
 
How is the electric discharge generated? 
The electric organs are produced of modified muscle or nerve cells known as electrocytes. They receive synchronized command signals from the brain to fire. When firing, the electrocytes are asymmetrically polarized acting as serially connected batteries.
Weak electric organ discharges (EODs) are divided in two types: pulse and wave.
Can electric fish give you an electric shock?
Most of them can't! The majority of the electric fish species only produce weak EODs (ranging from 10Hz to 2000Hz). It is used to navigation and communication. In addition to weak EODs, the electric eels (genus Electrophorus) generate strong EODs up to 860V for hunting and self-defense (Animation 3).

Animation 1: Pulses EODs are brief all-or-none events of the order of 1 ms or a few milliseconds separated by much longer intervals (orange graphic in the bottom). Heard in a speaker (turn speakers on!), a buzzing sound or single clicks at very low discharge rates are heard. As for example, in species of banded bluntnose electric knifefishes (genus Steatogenys).

Animation 2: Wave EODs have no pauses between them. Thus that they represent a continuous wave and are of a constant frequency that may be modulated when the fish is excited (orange graphic in the bottom). Heard in a speaker (turn speakers on!), wave EODs sound like a musical instrument playing a constant tone. As for example, in species of glass electric knifefishes (genus Eigenmannia).

Animation 3: Electric eels possess three electric organs: Main, Hunter’s and Sachs'. Main and Hunter’s electric organs produce high voltage electric organ discharges (used to self defense and predation) and Sachs' generates the low-voltage EODs (pulse EODs used to navigation and communication). Nonetheless, all three electric organs fire during the high-voltage EODs. Electric organs are composed by thousands of electrocytes organized as batteries in series. Electrocytes when at rest, have negative ion charge inside (relative to the positive ion outside) and therefore a charge of 0 mV. However, when activated (by the motor neuron activities) the positive ions flow inside the electrocyte, causing a potential reverse of c. 150mV. So, when the electrocytes are excited at the same time they produce voltages up to 860 V. 

Fed in a speaker, electric eel pulse EODs are single clicks that can be slow (eel resting or swimming slowly) or fast (eel swimming fast) depending on the fish's activity

Did you know that electric eels hunt in group?

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Behind the Scenes: exhibit at National Zoo