What happens to echinoderm larvae when they metamorphose into adults?

Echinoderms have swimming larvae that are bilaterally symmetrical, with left and right sides, but they do not 'develop into' bottom-living adult echinoderms, which are radially symmetrical, often star-shaped. The juvenile (young adult), radial from the start, grows from a group of stem cells within the larva. It gradually moves to the outside of the larva, and the larva and juvenile develop side-by-side. In most cases, the larva eventually settles and shrivels, and the juvenile crawls away. In one species of starfish, however, the juvenile drops off the swimming larva, which can go on swimming for a further three months.