The mystery of how some fish change their sex has been unlocked, scientists say.
Around 500 species such as clownfish made famous by Finding Nemo, the kobudai from Blue Planet II, and the Caribbean bluehead wrasse, routinely change their sex in adulthood as a natural part of their life cycle.
Most bluehead wrasses begin life as females, but can become males later in life in a process that takes 10 to 21 days, researchers say.
Dr Erica Todd, of the Department of Anatomy in New Zealand, said: “When a dominant male is lost from a social group, the largest female transforms into a fertile male in 10 days flat.
“Females begin this transformation within minutes, first changing colour and displaying male-like behaviours.
Read on...Support us and go ad-free
“Her ovaries then start to regress and fully functional testes grow in their place.
“How this stunning transformation works at a genetic level has long been an enigma.”
A study published in Science Advances used the latest genetic approaches, high-throughput RNA-sequencing and epigenetic analyses, to see how and when specific genes are turned on and off to allow the change.
Researchers found the sex change in bluehead wrasse involves a complete genetic rewiring of the gonad.
Genes needed to maintain the ovary are first turned off, and then a new genetic pathway is steadily turned on to promote testis formation, the University of Otago-led study suggests.
This chain reaction begins when a gene called aromatase, which is responsible for making the female hormone oestrogen, is turned off.
What triggers this reaction is unknown, but the stress of losing the existing dominant male may be an important signal in turning off the genetic pathway that maintains the ovary.
Co-lead author, PhD candidate Oscar Ortega-Recalde, said: “In fish and other vertebrates, including humans, cells use chemical markers on DNA that control gene expression and remember their specific function in the body.
“Our study is important because it shows that sex change involves profound changes in these chemical marks.”
Dr Todd added: “Understanding how fish can change sex may tell us more about how complex networks of genes interact to determine and maintain sex, not only in fish but in vertebrate animals generally.”Support us and go ad-free
We know everyone is suffering under the Tories - but the Canary is a vital weapon in our fight back, and we need your support
The Canary Workers’ Co-op knows life is hard. The Tories are waging a class war against us we’re all having to fight. But like trade unions and community organising, truly independent working-class media is a vital weapon in our armoury.
The Canary doesn’t have the budget of the corporate media. In fact, our income is over 1,000 times less than the Guardian’s. What we do have is a radical agenda that disrupts power and amplifies marginalised communities. But we can only do this with our readers’ support.
So please, help us continue to spread messages of resistance and hope. Even the smallest donation would mean the world to us.