The effect of social isolation on androgen and corticosteroid levels in a cichlid fish (Haplochromis burtoni) and in swordtails (Xiphophorus helleri)
Hannes, R.P.; Franck, D.
Hormones and Behavior 17(3): 292-301
ISSN/ISBN: 0018-506X PMID: 6685686 Accession: 021917707
The blood androgen and glucocorticoid levels of male H. burtoni and X. helleri were measured in socially isolated individuals (8 and 4 wk, respectively) and nonisolated controls. In both species isolation leads to significant reductions of mean concentrations and variances, both for androgens and corticosteroids. It is known for H. burtoni, and new evidence for X. helleri is presented, that social isolation reduces aggressivity in nonescalating situations. It is proposed that social stimuli in both species stimulate the testes to produce more androgenic hormones, leading to higher levels of aggression. In tropical fish species the androgenic optimum for defending a territory or a social status may be much more controlled by social stimuli than previously realized.