In starfish, the sperm or eggs are produced in testes or ovaries, respectively, which fill the arms during the reproductive season. The animals shed their sperm and eggs into the water. Individual starfish detect gametes of their own species in the water, and they respond to that stimulus by releasing their own gametes. Fertilization takes place in open water, and larvae swim around for some time as members of the huge community of plankton that swarm in the ocean. Eventually the larvae, which have bilateral symmetry, swim to the ocean bottom, where they mature and metamorphose into adults that have radial symmetry.
Many starfish have incredible abilities to repair themselves when damaged.
In fact, if a starfish is pulled into pieces, each piece can grow into a new animal as long as it contains a portion of the central part of the body. In the past, angry shellfishermen who were aware that starfish ate bivalves would tear the animals into two or three pieces and toss them overboard. Imagine their surprise when they noticed even more starfish in their bivalve beds. Today, shellfishermen know that starfish have the ability to regenerate and that every piece of torn starfish they throw back could develop into a completely new organism.