Drug Elicitation of the Aggressive Display in Siamese Fighting Fish, Betta splendens

Experiment I tests the hypothesis that sympathomimetic
amines serve to facilitate or trigger the aggressive display
of the Siamese fighting fish. Three drugs were used to
test this theory: amphetamine, norepinephrine and Dibenzyline.
Amphetamine was administered to a group of six females while
norepinephrine and Dibenzyline were given to males.
Fish were all maintained in the laboratory for one
week before any testing began. Each of the three parts of
Experiment I was conducted in the same way. The Bettas were
tested first with no drugs in their water to determine their
baseline level of activity. Two to four days later, the fish
were tested with either 40 mg of amphetamine, 70 mg of norepinephrine
or 4.5 mg of Dibenzyline. Another control trial
was run two to four days later and then another experimental
trial after the same period of time. Results indicated that amphetamine increased fin
flaring frequency and duration in female Bettas. The norepinephrine
had the effect of increasing gill plate extension
frequency and duration. Also the norepinephrine increased
time to habituation. Dibenzyline was shown to influence fin
flaring frequency and duration. A strong adrenergic blocking
agent, Dibenzyline greatly decreased the aggressive display
activities but did not significantly alter general activity.
The measure of general activity used was latency to feeding.
All fish were deprived of food for four days and considered to be hungry.
In Experiment II, 16 female Bettas, eight experimental
and eight control, received a 25-day treatment with
either methyl testosterone dissolved in alcohol or plain
alcohol. All fish were tested before any treatment was
given and assigned to groups on the basis of the behavioral
measure of fin flaring so as to match the experimental and
control groups as closely as possible. The experimental
fish then were given .2 cc of methyl testosterone (1mg/cc)
and the controls were given .2 cc of alcohol. The treatment
in all studies was added to the water of the living tank.
After 25 days, all Ss were retested to determine
what, if any, effects the testosterone had on the display
activities being measured.
The hypothesis that testosterone would cause an
increase in growth rate and colorfulness was not supported by
the data. There were, however, significant increases in fin
flare frequency and duration and in the average length of a
fin flaring response. There was some tendency toward an
increase in gill plate extensions as well, but this was not
large enough to gain statistical significance.