Platyhelminthes are divided into three classes: turbellarians (or Turbellaria), trematodes (or Trematoda) and cestodes (or Cestoda).
Turbellarians are free-living platyhelminthes and their main representative is the planaria (Dugesia tigrina). Trematodes are parasites, they live inside a host and the schistosome ( Schistosoma mansoni) that causes schistosomiasis is an example. Cestodes are parasites too, they do not have digestive tubes and their cells are nourished by absorption of nutrients from the host; their most popular representative are the beef and pork taenias (Taenia saginata and Taenia solium) that parasite humans.
