Trematode

The Trematodes are a class of flatworms in the phylum Platyhelminthes. They are called flukes, and 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, which is the agent of dispersal, is usually a snail.

The trematodes or flukes are estimated to include 18,000Littlewood D.T.J. & Bray R.A. 2000. The Digenea, in Interrelationships of the Platyhelminthes.  
Systematics Association Special Volume #60, pp168–185.  to 24,000 species.

 References 

Category:Flatworms
Category:Parasites