School of sea goldies in a coral reef with feather stars, Great Barrier Reef, Queensland, Australia

A goldie gala

It's ladies' night at the Great Barrier Reef. Boasting bright orange-pink colouration, this school of sea goldies appears to be all-female. But that could change quickly – sea goldies are protogynous hermaphrodites, meaning that when there aren't enough fellas around, the largest females change sexes to become male, turning purplish and growing even larger. All goldies are born female, but those that switch to males enjoy instantly better odds at mating time. For every male goldie there are up to 10 females.