I’m a Reef keeper and have multiple wrasses in my tanks. They are one of the species of fish that can change sex at will (usually, you’ll see). All species of wrasse can self-determine on any given day what sex they want to be. Typically they will only change sex if they aren’t mating, for example if you take three female bluestar leopard wrasses (one of the species I own) and put them in one tank, then one of them will change from this beautiful female
To this pretty boring male
As I want the showier female, I purposefully only keep one bluestar leopard wrasse in my tank and so far she has stayed a beautiful elegant female.
But not all species of wrasse are like that. Most species of wrasse have more brilliant looking boys and you want that. And some have a third sex.
The Lineatus Wrasse all start out as females and just like my other wrasse they can go back and forth from male to female at will.
Usually you start with females which are nice enough but semi bland
And if you have three of them then one will turn into a male typically and they’re a little showier.
But if you get three or more males together, then one of them will switch to a third sex called a Supermale. Once they become a Supermale, they never switch back. But that’s great because Supermales are ultimately super showy. Fabulous even.
It’s a little easier to see the three sexes in the Flame Fairy Wrasse
Female and male
And the flamboyant Supermale
There are plenty of animals which not only can they switch sex or be both at the same time, but take on a third sex.