Like most echinoderms, A. planci reproduces sexually through broadcast spawning. The female releases millions of eggs into the water column that are fertilized by a male's sperm. Fertilized eggs develop into planktonic larvae, which depend on phytoplankton for nutrition while they pass through several developmental stages, from gastrula to bipinnaria to brachiolaria. Near the end of the brachiolaria stage, the larva settles onto a suitable hard surface and metamorphoses into a juvenile starfish. Its arms will begin to develop as it matures. The juvenile starfish begins with 5 arms, which will increase to as many as 21 arms by adulthood.
Researchers note three age classes for A. planci: juvenile, sub-adult, and adult. Growth rates are age-specific: growth is rapid for juveniles (up to 16.7 mm per month) while the rate slows as they transition from sub-adult to adult (4.5 mm per month).
Development - Life Cycle: metamorphosis ; indeterminate growth