Bipinnaria transforms into brachiolaria larva which develops three short arms at preoral lobe, known as brachiolar arms (one median and two lateral arms). They contain coelomic extensions and adhesive cells at their tips. An adhesive glandular area at their base acts as a sucker. Appearance of the sucker marks the beginning of metamorphosis.
Metamorphosis of brachiolaria. With the help of adhesive structures it attaches to some object. Anterior region acts as stalk for sop.ctime, while posterior part, having gut and coelomic chambers, converts into a young star. This star detaches itself and starts leading a free life. Some species cut short the development as a result of deletion of some larval stages. In astropecten, the brachiolaria stage is missed with the result bipinnaria directly metamorphoses into adult with in 2-3 months. In Asterina gibbosa, bipinnaria stage is omitted, larva develops an adhesive apparatus, as brachiolar arms and sucker, and undergoes metamorphosis. Still in Luidia, a giant and peculiar is formed which is called as bipinnaria asterigeara.
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