Leeches may also be used to treat black eyes. And hirudin, the anticoagulant, may be used in the treatment of inflammation of the middle ear. Hirudin may also eventually be used in invitro blood sampling. Researchers have found that the anticoagulant and clot-digesting properties of substances in leech saliva make them potentially useful for the treatment of heart attacks and strokes. Plus, researchers are looking into the possibility of synthetically engineering leech saliva to be used for all these purposes.
Sanguivorous leeches can ingest several times their own weight in blood at one meal.
They generally attach themselves to their meal with their anterior sucker, and some have a proboscis they insert into their prey from their mouth. Others may use strong jaws to cut into through the tissues of their prey. 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.