Today's parasite is commonly found in freshwater fishes of the Palaearctic region. This particular worm has evolved to skip a few steps to the usual three-host life-cycle of most digeneans. Asymphylodora tincae uses a snails as a first intermediate host, where larval stages known as cercariae are produced through asexual multiplication - so far so usual for digeneans. However, instead of leaving the snail like most digeneans, the tailless cercariae stay inside the snail. Additionally, instead of then developing into the cyst-like metacercariae stage as a prelude to infecting the definitive host, this species has done away with that altogether. The cercariae of A. tincae can directly infect the fish definitive host, which occurs when the fish consumes an parasitised snail.
Reference and photo source:
Našincová, V. and Scholz, T. (1994) The life cycle of Asymphylodora tincae (Modeer 1790) (Trematoda: Monorchiidae): a unique development in monorchiid trematodes. Parasitology Research 80:192-197.
Contributed by Tommy Leung.