Redescription of Macroorchis spinulosus Ando, 1918 (Digenea: Nanophyetidae) encysted in the fresh water crayfish, Cambaroides similis.

Macroorchis spinulosus Ando, 1918 (Digenea: Nanophyetidae) is redescribed based on adult flukes recovered from experimental mice, rats and cats which were fed with metacercariae encysted in the muscle of the crayfish. Cambaroides similis. A total of 117 adult flukes were harvested from the small intestine of the experimental animals at 5-21 days post-infection. The worm recovery rate was 31-37%, not significantly different among the three kinds of animals. The metacercariae were round, 0.18 mm in average diameter, encysted with two layers of thick walls, and possessing a stylet on the oral sucker and Y-shaped excretory bladder. The adult flukes were oval, 0.66-0.71 mm long and 0.36-0.41 mm wide, and characterized by the presence of a stylet on the oral sucker, variable location of the ovary near the mid-portion of the body, bilobed seminal vesicle, and anterolateral location of two testes. These morphological features were a little different from the original description, hence, an emended version of M. spinulosus was given. M. spinulosus is a new intestinal trematode of animals and possibly man in Korea.