Light Lab

Purpose:
In this experiment, we will examine the effects of different magnitudes of light upon the electric organ discharge (EOD) and the be havior of Gnathonemus petersii. We will observe the position of the fish, the sound of the EOD, and the electric wave displayed on the oscilloscope.
Materials:
Live weakly electric fish
Electrode

Oscilliscope
Amplifier

preamplifier
55 gallon tank

15 Watt light bulb
100 Watt light bulb

Procedure:
Turn on the oscilloscope (wait 30 seconds for it to warm up).
Observe the fish for 5-10 minutes.
Record behavior of fish on a recording sheet
Record the behavior of the fish, the amplitude (up or down), frequency (up or down), and millivolts (positive/negative) of the electric organ discharge, along with any extra comments and observations.
Turn on a 15 watt light bulb on the side closest to the electrodes (which should be attached to wooden dowels with string ; see diagram).
Leave the light on for two minutes and observe how the fish reacts on a recording sheet
Turn off the light
Observe the reactions of the fish for five more minutes on a recording sheet.
Repeat steps 4 through 6 two more times, but leave the light on for five minutes the first time and for ten minutes the second time. (Note: do not perform each experiment consecutively, do them at different times so as to allow the fish sufficient time to recuperate.)
Conduct this experiment again with a 100 watt light bulb.

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