Digenea simplex is a type of parasitic flatworm belonging to the class Trematoda. It primarily infects the intestines of various fish species, where it can cause health issues for the host. This organism has a complex life cycle that often involves multiple hosts, including snails and fish. The adult Digenea simplex resides in the intestines of fish, where it reproduces and releases eggs. These eggs are then expelled into the water, where they hatch into larvae. The larvae must find a suitable intermediate host, typically a snail, to continue their development before eventually infecting fish.