The Trematoda is a class within the phylum Platyhelminthes that contains parasitic worms, commonly referred to as flukes. The Trematoda have 18 000 to 24 000 species. Trematodes are parasites of molluscs and vertebrates. All trematodes infect molluscs and most have a complex life cycle involving other hosts. Most trematodes are monoecious and alternately reproduce sexually and asexually.

Photo Credit: Photomicrograph of the Australian Aspidogastrean Lobalostoma manteri.

Taken by the Queensland Museum.