Reproductive System of Asteroidea
Sexes are separate in several asteroids. There are ten (10) gonads, two in each arm. They emerge tuft-like or as cluster of grapes. Mature gonads occupy approximately to the entire arm. The gonopore is located between the bases of the arms. In the majority of sea stars the sperms and eggs are shed into sea water and fertilisation is external. A single female might shed as many as 2.5 million eggs. Development involves a larval stage - the bipinnaria larva. The free swimming larva is provided with ciliary bands and arms which function in both locomotion and feeding. The bipinnaria larva then transforms into another larva, the brachiolaria larva along with the appearance of additional arms at the anterior end. The branchiolaria as compared to metamorphoses into an adult.