fish get frisky quick.
by Neil Caudle
In a new study of cichlid fish native to East Africa’s Lake Tanganika, Sabrina S. Burmeister, assistant professor of biology, found that subordinate male fish underwent a quick transformation when more-dominant males were removed.
“When we took dominant cichlid males from an experimental tank, subordinate males started becoming dominant themselves in as few as two minutes,” Burmeister says. “Their colors—blue and yellow—got much brighter, a black stripe we call an eye bar appeared near their eyes, and they became much more aggressive than they were before. The remaining males also paid a lot more attention to females because for the first time, they had an opportunity to reproduce.” Previous studies had found that such changes took as long as a week and were associated with increased fertility.
Taking the next step, Burmeister and colleagues analyzed brain tissue and found that perception of “social opportunity”—the opportunity to rise in the dominance hierarchy—caused more of a gene known as egr-1 to be expressed in the hypothalamus, a region of the brain that controls fertility. “We believe that in our fish, egr-1 turns on expression of a second gene, GnRH1, which produces a hormone necessary for reproduction,” Burmeister says.
The work has implications for humans because basic mechanisms that control reproduction in fish and in people are the same, Burmeister says.
Burmeister’s report of her experiments, conducted at Stanford University, appeared in the November 2005 issue of PloS Biology. Co-authors were Erich D. Jarvis and Russell D. Fernald, neurobiologists at Duke University and Stanford University, respectively.