School of sea goldies with feather stars, Great Barrier Reef, Queensland, Australia

© Gary Bell/Minden Picture

A goldie gala

It's ladies' night at the Great Barrier Reef: Their bright orange-pink coloration indicates these sea goldies are females. But that could change quickly: Sea goldies are protogynous hermaphrodites, meaning that when there aren't enough fellas around, the largest females change sex to become male, turning purplish and growing even larger. All goldies are born female, but those that switch to male enjoy instantly better odds at mating time: For every male goldie there are up to 10 females.