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Ladies before gentlemen

Neil Gemmell banner

Ladies before gentlemen

A study of how some fish change sex has potential benefits spanning aquaculture through to regenerative medicine.

Professor Neil Gemmell (Department of Anatomy) has received a grant from the Marsden Fund to investigate changes in fish that are “sequential hermaphrodites” – that is, they begin life as one sex and later reverse sex. Often this sex change is socially controlled, with the absence of a dominant male from a social group resulting in the largest female reversing sex to replace him.

The research project is investigating the molecular basis for what Gemmell calls “this stunning transformation”, which is unknown.

The research focuses on three species of fish that change sex from female to male: the common New Zealand spotty and two distant tropical relatives, the bluehead wrasse and the three-spot wrasse. Gemmell says in bluehead wrasse, the entire sex change – which entails a complete restructuring of the gonad – takes only about three weeks.

Gemmell says many valuable commercial species, including blue cod and snapper, change sex during their life cycle. Understanding the process could be useful in terms of being able to manipulate sex in farmed fish and wild fisheries to help improve stock management and production.

He says there are also possible medical benefits from understanding how the gonad in sex reversing species is completely re-engineered from an ovary to a testis. “It may be that the pathway can be manipulated in other contexts so that we can ultimately change one human organ to another.”

Photo: Graham Warman