Interestingly, the little orange and white swimmer experiences a change in the brain long before a change in its reproductive organs. According to researchers at the University of Illinois, if a female clownfish dies, her mate takes over her duties of guarding their nest and eggs within an anemone. Over the course of six months, the male's brain chemistry changes. Its preoptic area grows to the size of a female's, it exhibits other behaviors only seen from that sex, and other fish interact with it as they would other females. The creature's brain and mannerisms become indistinguishable from a female's.

Then the gonads begin to change, though not always. Some clownfish continue on for years with a female brain and male reproductive systems. Others develop female gonads, and begin producing and laying eggs. The female takes a male mate, restoring the gender balance and helping the species survive.

In 2016, scientists narrowed in on the specific genes that control this process.

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