Air Date: Week of October 21, 2005

Living on Earth's Emily Torgrimson reports on dominance and genetics in the cichlid fish.

Transcript

TORGRIMSON: How do you turn a wimp into a leading man? Just remove his competition.

So say researchers who work with the cichlid fish, a species that lives in the freshwater lakes of East Africa and abides by strict social hierarchies. In a study conducted at Stanford University, scientists found that when the dominant fish is removed from a tank of cichlids, a subordinate male will undergo a rapid and dramatic transformation to fill his rival’s place.

Within minutes their coloring begins to change from gray to the flashy yellow and blue of a dominant fish. Prominent black stripes called “eyebars” also emerge – the cichlid equivalent of trading in blue jeans for a power suit. The researchers also discovered that the newly-dominant fish begin behaving far more aggressively, making threatening displays and chasing others around the tank. And, of course, they also start taking a more active interest in female cichlids.

These changes take place just twenty minutes after the male begins his social climb. The cichlids’ rapid makeover seems to be caused by a specific gene responsible for ramping up hormone production. Scientists were struck by the speed at which a social factor – the absence of a dominant male – was able to trigger a response in the fishes’ genes. They hope that these findings will help shed light on the complex interaction between genetics and environment.

That’s this week’s Note on Emerging Science, I'm Emily Torgrimson.