Flukes: Trematoda

Flukes (FLOOKS) are flatworms that are parasites (PAIR-uh-sites), which are animals or plants that live on or in other animals or plants, or hosts, without helping them and usually harming them. Flukes usually are leaf shaped and have suckers that they use for attaching to and feeding on their hosts. Flukes can be as small as one–thirty-second of an inch (1 millimeter) or as long as 23 feet (7 meters), but most are one-eighth to 2 inches (5 millimeters to 5 centimeters) long. Flukes have a hard covering that keeps them from being dissolved by the stomach juices of their hosts.

There are two types of flukes. One type has a direct life cycle, meaning there is only one host, often freshwater snails, in which development from egg to adult occurs. The other type of flukes has an indirect life cycle, meaning they infect different hosts during the various stages of life. Most of these flukes have two stages of development and at least two hosts.