Getting on top, genetically

Take the bully out of the schoolyard and another quickly takes his place.

By | November 7, 2005

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© 2003 National Academies of Science

Take the bully out of the schoolyard and another quickly takes his place. 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 increasing fertility. They also express egr-1, a transcription factor that likely triggers enhanced fertility and other long-term dominance traits, according to Russell Fernald at Stanford University and his colleagues.1

Researchers gave subordinate fish an opportunity to ascend in a familiar environment by removing the dominant male from a tank containing two males and four females.

The researchers used in situ hybridization to analyze gene expression in the fish's brains. Ascending males had more than twice as much egr-1 expression in the anterior preoptic region as males who had remained either subordinate or dominant. The authors found an egr-1 recognition site in the gonadotropic-releasing hormone-1 (GnRH1) gene, which regulates reproductive physiology in all vertebrates, suggesting a likely target for the transcription factor.

The work "speaks to how dynamic these [social] situations can be and how natural selection has probably selected for these very, very rapid responses," says McMaster University behavioral psychologist Sigal Balshine.

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