The biology of ribbon worms is a panoply of peculiarities. For example, take the way they develop. Not content with simply transforming from one form into another, many species of ribbon worm have added an intriguing twist to metamorphosis. The juvenile ribbon worm grows from a bud of cells in a planktonic larva (pilidium). When the time comes for the young worm to fend for itself it breaks free from the larva and consumes the now useless vehicle – essentially eating itself.
Here’s a video from the Maslakova lab in Oregon: