Rf. Oliveira et al., SOCIAL MODULATION OF SEX STEROID CONCENTRATIONS IN THE URINE OF MALE CICHLID FISH OREOCHROMIS-MOSSAMBICUS, Hormones and behavior, 30(1), 1996, pp. 2-12
The relationship between urinary concentrations (free + sulfates + glu
curonides) of the steroids testosterone (T), 11-ketotestosterone (11 K
T), 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) and 17
alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 alpha-P), and the socia
l behavior of males of the cichlid fish Oreochromis mossambicus was in
vestigated. After 8 days of isolation none of the steroids were good p
redictors of social dominance developed after subsequent formation of
all-male groups. One day after group formation dominance indexes were
good predictors of the urine concentrations of all sex steroids. Domin
ance indexes and androgen concentrations measured after all-male group
formation were positively correlated with territoriality, courtship r
ate, and nest size. Similar relationships were found for progestins wi
th the exception that they were not correlated with courtship rate. Al
l-male group formation was also accompanied by an increase in urinary
sex steroid concentrations in fish that became territorial and a decre
ase in non-territorial fish with the exception of T, which increased i
n both groups. Addition of ovulating females caused steroid concentrat
ions to return to levels near isolation, except for 17,20 alpha-P in t
erritorials, which underwent a large increase. Thus, social interactio
ns may have an important modulatory effect on sex steroid concentratio
ns in O. mossambicus. (C) 1996 Academic Press, Inc.