Some species of fishes such as sharks and rays are born one sex and stay that sex throughout life. For others, such and the wrasses Family Labridae and parrotfishes Family Scaridae sex reversal is the norm. For species that change sex there may be up to three colour phases. The first is a juvenile phase colouration shown by immature fishes. As a juvenile fish grows it develops the initial phase IP colouration. This may resemble the juvenile phase colouration or be quite distinct.
The incredible world of sex-changing fish #OurBluePlanet #BluePlanet2 | Our Blue Planet
The bluehead wrasse is a fish that lives in small social groups in coral reefs in the Caribbean. Only the male has a blue head — signalling his social dominance over a harem of yellow-striped females. If this male is removed from the group, something extraordinary happens: the largest female in the group changes sex to become male. Her behaviour changes within minutes.
Fish are the sex-switching masters of the animal kingdom
We wanted to tell a story of seasonal change in One Ocean and to show how small changes in temperature can have a big influence on marine life in the seasonal seas. Our team then began to investigate and discovered that a rise in sea temperature triggers the males to engage in territorial battles over the right to spawn, and more interestingly, that all the big males that fight were once females. Having studied marine biology it was no surprise to me that kobudai change their sex. After all it is a member of the wrasse family who are well known to exhibit sequential hermaphroditism, meaning that for them sex change at some point in their life is a normal biological process generally to aid reproductive success.
Miranda Dyson explains the biological process Copyright: BBC In the first episode of Blue Planet II we met the Kobudai — the Asian sheepshead wrasse - that was introduced as a female, behaved like a female and looked like a female. And then, as we watched she slowly but surely morphed into a male — displayed male behaviours and developed male characteristics. It may seem strange but in fact it's common among fish.