To locate and identify nearby objects and to "talk" with others of their species, weakly electric fish generate weak high-frequency (0.1-10kHz) electric fields. Brian Rasnow and Chris Assad measured the electric organ discharge (EOD) of these fish with a robotic microvoltmeter at high time and space resolution. Then Rasnow and Assad assembled the EOD measurements to make "pseudocolor" QuickTime movies of the fishes' electrical organs at work. In these movies (which you can view below), light blue represents zero; and green, yellow, and red represent successively greater positive electrical output. Blue, dark blue, and violet represent successively negative values of the electrical potential and field magnitude. The movies are shown in very slow "motion" -- at the fastest they are 1/4000 the actual electric organ discharge speed.

-- Kathleen Stein

• Apteronotus leptorhynchus (brown ghost knife fish) #1
• Apteronotus leptorhynchus #2 -- electric field
• Apteronotus albifrons (black ghost knife fish)