What is "trematoda"

Trematodea \Trem`a*to"de*a\, n. pl. [NL., from Gr. ? having holes, from ?, ?, a hole.] (Zo["o]l.) An extensive order of parasitic worms. They are found in the internal cavities of animals belonging to all classes. Many species are found, also, on the gills and skin of fishes. A few species are parasitic on man, and some, of which the fluke is the most important, are injurious parasites of domestic animals. The trematodes usually have a flattened body covered with a chitinous skin, and are furnished with two or more suckers for adhesion. Most of the species are hermaphrodite. Called also Trematoda, and Trematoidea. See Fluke, Tristoma, and Cercaria.

Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.

They are internal parasites of molluscs and vertebrates. Most trematodes have a complex life cycle with at least two hosts. The primary host, where the flukes sexually reproduce, is a vertebrate. The intermediate host, in which asexual reproduction occurs, is usually a snail.