(also referred to as Pseudophyllidean) tapeworms
Adult Diphyllobothrium spp. occur in the small intestine of fish-eating mammals. Adults are 2-12 m long, yellowish-grey in color with dark central markings caused by the centrally located uterus and eggs. With an indirect life-cycle, Diphyllobothrium latum uses first a copepod to harbor the development of the coracidium to a procercoid, and then fresh-water fish as a second intermediate host where the pleurocercoid develops. These pleurocercoids accumulate in the fish and are then infective to mammals ingesting them.
In place of having suckers on the scolex, as many members of other classes of cestode have, Diphyllobothrium has two narrow, deep muscular groves called bothria. These bothria are often indistinct. It's name, a borrowing from the Greek di- (two) + phyllodes (like leaves) + bothrion (trench); reflects the morphology of its scolex.