marine leech

Marine leeches are segmented worms belonging to the phylum Annelida. While most leeches are found in freshwater, some species inhabit the sea. These annelids are characterized by a small sucker at the anterior end, which contains the mouth, and a larger sucker at the posterior end. Leeches have 34 body segments and can range in length from very small to over 18 inches.12

Leeches can be predators, feed on organic debris, or be parasitic. Some marine leeches attach to and feed directly from the gills of fish. They breathe through their skin and possess a digestive system capable of storing food for extended periods. Leeches are hermaphroditic, meaning they have both male and female reproductive organs, but they require cross-fertilization. Their saliva contains substances that anesthetize the wound, increase blood flow, and prevent clotting, with the anticoagulant hirudin being a notable example used in medicine.23