Secrets of a sex-changing fish revealed

About 500 species of fish  in adulthood, often in response to environmental cues. How these fish change sex has, until now, been a mystery.

The secrets of fish that change sex have, for the first time, been revealed by an  led by New Zealand scientists and including La Trobe University geneticist and Prime Minister's Prize for Science winner 2017, Professor Jenny Graves. The findings were published today in the prestigious journal, Science Advances.

Bluehead wrasses live in groups, on coral reefs of the Caribbean. A —with a blue head—protects a harem of yellow females. If the male is removed, the biggest female becomes male—in just 10 days. She changes her behaviour in minutes, her colour in hours. Her ovary becomes a testis and by 10 days it is making sperm.
Using the latest genetic approaches—high-throughput RNA-sequencing and epigenetic analyses—the researchers discovered when and how  are turned off and on in the brain and gonad so that sex change can occur.
"Genes needed to maintain the ovary are first turned off, and then a new genetic pathway is steadily turned on to promote testis formation."

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