Sea stars have separate sexes. In the PNW, the majority spawn in late winter or early spring, generally coincident with the spring phytoplankton bloom. Paired gonads in each arm broadcast sperm or eggs into the water through pores located at the bases of the arms. Hundreds of thousands to millions of eggs and sperm are shed directly into the water where chance fertilization takes place. A few species brood their young: sperm is shed by males in the normal way but the female retains the eggs beneath her arched body or in a specialized internal cavity. The life expectancy of sea stars is mostly unknown but is thought to be only a few years. However a well-fed rose star reportedly lived for more than 20 years in an aquarium.
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