MALE fish that win a power struggle become less stressed and more sexy,
say researchers at Stanford University in California. They say the same could be
true of men.
The team monitored levels of cortisol, a stress hormone, in African teleost
fish (Haplochromis burtoni). To reshuffle their social hierarchy, they
transferred the fish to a new tank, where fish that had been dominant lost the
associated bright coloration. During the struggle for territory that followed,
all the males had high cortisol levels.
Once new fish had established dominance, however, signalled by
brighter-coloured scales, their cortisol levels fell. They also grew heavier
testes and larger sex-related neurons in their brains.
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鈥淲hen you switch an animal鈥檚 social state, the neurons change size,鈥� says
Stephanie White, an author of the report in this week鈥檚 Journal of
Neuroscience (vol 17, p 6463). Her colleague Russell Fernald says that
changes in social status can alter the physiology of many animals, including
humans. 鈥淲e can鈥檛 imagine that what we鈥檙e finding won鈥檛 be generally true,鈥� he
says.