"During the experiment, I would remove the dominant male one hour before the lights came on," she says. "We used this nighttime-kidnap-the-bully approach as a gentle way of not disturbing other fish in the tank."
Burmeister observed that after the lights came on, the subordinate male quickly determined that no dominant rival was in the tank and rapidly began his ascent toward domination. In minutes his coloring changed, his eyebar appeared and he began making threatening displays and chasing other fish. "Once they start changing, there's no question they'll become dominant within 2 to 10 minutes," Burmeister says. "It's like they decide to go for it: They know their place in the hierarchy, and they make a decision to change."
After 20 minutes, the ascending males were sacrificed and their brain cells prepared for laboratory analysis. The researchers wanted to see if they could identify the genes responsible for triggering the ascent to sexual dominance. They were particularly interested in a gene called egr-1, which produces a regulatory protein that activates other genes. The research team hypothesized that, when a male encounters an opportunity to climb the social ladder, the egr-1genes in his brain send an immediate signal to the gonadotropin-releasing hormones cells to start growing. As these cells get bigger, they crank out more and more hormones, transforming the male from doormat to dominant within 10 minutes.
In fact, laboratory analysis confirmed that there was twice as much egr-1 gene expression in the brain cells of ascending cichlids than in either dominant or subordinate males, suggesting that the erg-1 gene plays a crucial role in jumpstarting the whole physical transformation.
"This is the first study where I have seen gene activ