For anemonefish, sex change happens first in the brain

Faculty in the News: Justin Rhodes, Professor Psychology


Anemonefish spend their whole lives in close proximity to their anemones. Females are larger and defend the nest; males tend to the eggs. (Photo by L. Brian Stauffer.)

Neuroscientist shines new light on a natural phenomenon:  The anemonefish is a gender-bending marvel. It starts out as a male, but can switch to female when circumstances allow, for example, when the only female present dies or disappears. In a new study, researchers found that the male-to-female sex-change occurs first in the fish’s brain and only later involves the gonads – sometimes after a delay of months or years.

“We discovered that when you pair two males together, they fight, and the winner becomes female,” said University of Illinois psychology professor Justin Rhodes, a behavioral neuroscientist who led the research. “But the first thing that changes is the brain, in particular the part of the brain that controls the gonads.”

The findings, reported in the journal Hormones and Behavior, describe the first known example of an animal undergoing a sex change in the brain before it occurs in the sex organs, the researchers said.

Keep reading