The beautiful Ribbon Eel (Rhinomuraena quaesita) changes colour and sex as it grows.
It is black with a yellow dorsal fin when young, but changes to bright blue with a yellow fin when it matures as a male.
These eels are the only protandic Moray Eels, which means that they change sex when they reach a body length of about 1.3 m (4 ft).
Then, the males turn yellow with white fins and become fully functional females.