Kuwait University

Life Cycles

  • Digenetic trematodes have complex life cycles with a definitive host and one or more intermediate hosts. The definitive host is usually a vertebrate carnivore, in which the adult trematode lives.
  • The trematode eggs are released from the definitive host into the environment, where they hatch into a free swimming stage called a miracidium, which penetrates snail first intermediate host.
  • Once in a snail, each miracidium produces numerous embryos of the next larval stage, redia or sporocyst.  Each redia or sporocyst, in turn, contains numerous embryos of a third larval stage, which is either another redia, sporocyst or a swimming larval stage called a cercaria.
  • The cercariae exit the snail and swim vigorously around until they encounter a suitable definitive host or second intermediate host. The cercariae transform into adults in the definitive host or form cysts (metacercariae) on the surfaces or in the tissues of the second intermediate host. Definitive host acquires the parasite by ingesting metacercariae.






Copyright 2011, Kuwait University-College of Science - Dept. of Biological Sciences

Larval Trematode Diversity in Kuwait Bay