For the first time, scientists have directly linked social cues to an immediate genetic response in the brain, according to a new study in PloS Biology. Only minutes after subordinate male cichlid fish sense an opportunity to become socially dominant, they display dominant characteristics such as changes in color and behavior, and express egr-1, encoding a transcription factor that likely triggers enhanced fertility and other long-term dominance traits.

"People forget that social influences are pretty important," said study co-author Russell Fernald at Stanford University in California. "Here's the case where the social is everything. [It] regulates brain structure in a very direct way."

Characterized by a dynamic social hierarchy, the cichlid fish Astatotilapia (Haplochromis) burtoni can readily alter sexual capacities, and only dominant males are physiologically able to reproduce. "We were interested in understanding how this occurred at a mechanistic level, uncovering earliest steps that occur in the process,"...

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