Which frogs can change their gender and how?

Other than frogs and certain fish, what other animals have changed their gender in the wild?

• I know female swordfish can become male, and some frogs can change gender, but can other animals do it as well?

• Answer:

  Limpets change sex as they grow. Small ones are male and large ones are female. Many worms are "born" with their sex undetermined. If they come across a female in the first few weeks of their lives they become a male and begin mating immediately. If they don't, they become females. This is known as isogamy.