A third type of leech doesn't have jaws, so it must feed by swallowing small prey items whole. Leeches can only reproduce sexually, and unlike some worms, they are not capable of regeneration. Like earthworms, they have a clitellum, which is a region of thickened skin that in leeches is only obvious during the reproductive period. Mating typically involves the intertwining of bodies where each leech deposits sperm in the others' clitellar area. The sperm then make their way to the ovaries for fertilization.
Studies show that the cocoons are capable of surviving the digestive system of a duck.
The fertilized eggs are deposited in a tough gelatinous cocoon that is secreted by the clitellum and contains nutrients for the developing leeches. The cocoon is either buried in mud or affixed to submerged objects, and after several weeks or months the young emerge as small copies of the adults. In the family Glossiphoniidae, many species of leeches attach the cocoons directly to the ventral side of the parent. The parent is able to protect the young as they develop and provide prey for the young leeches after they hatch. Adult leeches die after they reproduce one or two times.