Social interactions tune aggression and stress responsiveness in a territorial cichlid fish (Archocentrus nigrofasciatus).
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.
Earley
Ryan L
RL
Department of Biology, Georgia State University, 24 Peachtree Center Ave. NE, Atlanta, GA 10 30303, USA. biorle@langate.gsu.edu
Edwards
Jonathan T
JT
Aseem
Obaidullah
O
Felton
Kathryn
K
Blumer
Lawrence S
LS
Karom
Mary
M
Grober
Matthew S
MS
D000374:Aggression / Q000502:physiology* / Q000523:psychology*; D000818:Animals; D049628:Body Size / Q000502:physiology; D005260:Female; D005399:Fishes / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood; D007398:Interpersonal Relations; D008297:Male; D009490:Neurosecretory Systems / Q000502:physiology; D011863:Radioimmunoassay; D013315:Stress, Psychological / Q000503:physiopathology* / Q000523:psychology*; D013731:Territoriality
D006854:Hydrocortisone