| Abstract: | A series of experiments were undertaken to demonstrate the dominance advantage of a territorial resident over an intruder (the prior residence effect) in the adult male Convict Cichlid (Cichlasoma nigrofasciatum) and to evaluate the effects of alcohol (ethanol) on this phenomenon. After successfully demonstrating the prior residence effect, additional experiments were conducted in which the resident or intruder was given one of three different doses of ethanol (0.15%, 0.20%, 0.35%). These doses have previously been shown to reduce or increase intraspecific aggression in this species Over the entire dosage range, drugging the intruder produced no changes in the dominance advantage of the resident. However, drugging the resident at the higher doses (0.20%, 0.35%) resulted in loss of the resident's dominance advantage. These effects were not due to impaired locomotor behavior of the drugged fish, as no abnormal motor behaviors were noted. In general, as reported in previous studies, the resident fish, whether drugged or not, typically attacked first. Also as has been previously shown, the fish that attacked (bit) first typically showed eventual dominance. The present results show that the dominance advantage of the territorial resident is not altered by giving an intruder a hypo- or hyperaggression-producing dose of alcohol. Changes in the dominance advantage occur only as a function of drugging the resident, thereby providing evidence that the behavior of the territorial resident is either directly or indirectly (reaction of the intruder to these changes) responsible for the prior residence effect. The present studies also provide some pharmacological approaches for determining the variables important in a laboratory analog of a naturally occurring instance of intraspecific aggression. |
