How Do Starfish Mate?

starfish-mate Credit: Danita Delimont/Gallo Images/Getty Images

Starfish can reproduce either sexually or asexually. Both male and female starfish exist, though they are externally indistinguishable from each other. They breed by releasing eggs and sperm into the water. The sperm fertilizes the eggs, and the resultant larvae eventually settle on the ocean floor to grow.

Starfish can also reproduce asexually. Starfish can regenerate an arm if it's lost. They can also regenerate their entire body from just one arm if a part of the central disc remains. The central disc is akin to the starfish's torso as it is the place where the arms attach. It functions as the activity center as well as the starfish's mouth.

To increase the chance of sexual reproduction, starfish usually gather in groups during spawning time. They may also communicate mating readiness through chemical signals. Once the eggs have become fertilized, they grow first into bipinnaria, which has just the mouth, ciliary bands and the anus. Brachiolaria larvae have more arms and an adhesive pit. At this stage they float through the water with plankton, which they eat to survive. They can swim by beating their cilia.

Polar and deep sea starfish often brood their young, with females holding the fertilized eggs on their surface or in the pyloric stomach. Starfish are not actually fish as they have no skeleton, gills or fins. Scientifically, they are described as sea stars.