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Advisor(s)
Abstract(s)
Androgens are known to respond to social challenges and to control the expression of social behavior and
reproductive traits, such as gonadal maturation and sperm production, expression of secondary sex characters
and reproductive behaviors. According to the challenge hypothesis variation in androgen levels above a breeding
baseline should be explained by the regime of social challenges faced by the individual considering the trade-offs
of androgenswith other traits (e.g. parental care). One prediction that can be derived fromthe challenge hypothesis
is that androgen levels should increase in response to social instability. Moreover, considering that a tighter
association of relevant traits is expected in periods of environmental instability, we also predict that in unstable
environments the degree of correlations among different behaviors should increase and hormones and behavior
should be associated. These predictions were tested in a polygamous cichlid fish (Mozambique tilapia,
Oreochromis mossambicus) with exclusive maternal care. Social instability was produced by swapping dominant
males among groups. Stable treatment consisted in removing and placing back dominant males in the same
group, in order to control for handling stress. Cortisol levels were also measured to monitor stress levels involved
in the procedure and their relation to the androgen patterns and behavior. As predicted androgen levels
increased in males in response to the establishment of a social hierarchy and presence of receptive females.
However, there were no further differential increases in androgen levels over the social manipulation phase
between social stable and social unstable groups. As predicted behaviors were significantly more correlated
among themselves in the unstable than in the stable treatment and an associated hormone–behavior pattern
was only observed in the unstable treatment.
Description
Keywords
Challenge hypothesis Social stability Androgens Cortisol Cichlids
Citation
Hormones and Behavior, 66, 369-382
Publisher
Elsevier