Clownfish can change their sex.
By D-32
They live in groups of one male, one female and several juveniles. If the female dies, the male’s sexual organs stop working, and previously dormant ovarian cells inside his body start making egg cells. He then takes the female place. To fill the vacuum left by this sex change, one of the juveniles then turns into an adult male. Therefore the sexual make-up of the group stays constant, and no breeding time is wasted.
By char1iej
The clownfish is able to live safely among the stinging tentacles of sea anemones by coating itself with a protective mucous coating. It gives scraps of food to the sea anemone, and the sea anemone protects the clownfish from predators with its stinging tentacles.
By Silvain de Munck