There is a fish called the angelfish （神仙鱼），which can change from female to male. No，it cannot do it by simply wishing to become male. The change happens for a speeifie reason.
The angelfish live in groups. And each group has one male fish，which is blue in colour，and four female fish，which are yellow in colour.
The male angelfish is the strongest and largest member of the group. When the male fish dies，the largest female fish in the group begins to change its looks. She begins to grow larger in size. After a week，she starts changing colour，from yellow to blue. Slowly，she begins looking like a male. Two weeks later，black stripes （条纹） appear on her body. She is now really male.
The angelfish are among the most brightly coloured fish of the sea. People prefer to keep them because of the interesting patterns （图案） on them. People like to keep them because of their good looking. Often，the young ones have different colours from the old ones. At night their colours may change.
