Social interactions tune aggression and stress responsiveness in a territorial cichlid fish ( Archocentrus nigrofasciatus)

• Published in: Physiology & behavior 2006-07, Vol.88 (4), p.353-363
• Main Authors: Earley, Ryan L., Edwards, Jonathan T., Aseem, Obaidullah, Felton, Kathryn, Blumer, Lawrence S., Karom, Mary, Grober, Matthew S.
• Format: Article
• Language: English
• Subjects: Aggression; Aggression - physiology; Aggression - psychology; Agnatha and pisces; Animal ethology; Animals; Behavioral psychophysiology; Biological and medical sciences; Body Size - physiology; Contest intensity; Cortisol; Experience; Female; Fishes - physiology; Fundamental and applied biological sciences. Psychology; Hormones and behavior; Hydrocortisone - blood; Interpersonal Relations; Male; Metabolic cost; Neurosecretory Systems - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Radioimmunoassay; Social isolation; Stress, Psychological - physiopathology; Stress, Psychological - psychology; Territoriality; Vertebrata
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2006.04.002

We examined the relative influences of pre-fight housing condition, contest intensity, and contest outcome in modulating post-fight stress hormone concentrations in territorial male convict cichlids ( Archocentrus nigrofasciatus). Individuals were housed either in isolation or in semi-natural communal tanks. Pairs of male cichlids that differed considerably in body mass were selected from the same housing regime. Pre-fight water-borne cortisol levels were obtained before allowing the dyad to interact until contest resolution, after which time post-fight cortisol levels were obtained from the winner and loser. There were no outcome-related differences in post-fight cortisol concentrations following escalated or non-escalated contests, a result that held true for both housing regimes. Pre-fight cortisol levels were significantly higher than post-fight cortisol levels, suggesting that initial confinement in a beaker for the water-borne hormone samples was a stressor, but that the animals acclimated quickly to confinement. Fights involving previously isolated participants were significantly more intense than those involving group-housed animals, which we explain as being a function of established relationships between social isolation, heightened acute cortisol responsiveness, and the expression of excessive aggressive behavior. Only group-housed losers demonstrated the ability to modulate aggression or hypothalamic–pituitary–interrenal (HPI) activity in a graded fashion to acute increases in cortisol or changes in contest intensity, respectively. We discuss a variety of factors that could disrupt the ability of isolates to appropriately modulate interactions between social behavior and the HPI axis, and we examine a number of functional hypotheses underlying the sensitivity of group-housed losers to changes in contest dynamics.