Development of the excretory bladder of the lung fluke Paragonimus ohirai (Trematoda: Troglotrematidae).

The excretory bladder of Paragonimus ohirai was studied during development in rats. Parasites were obtained at each development stage, and single worms were prepared for both transmission and scanning electron microscopy (SEM). During early transformation (1, 2 days), excretory materials such as calcareous concretions and lipid droplets filled the bladder, and Golgi complexes and various types of cytoplasmic bodies were abundant. The bladder epithelia of late transformation (3, 5 days) were characterized by dense granules and glycogen concentration around lipid droplets. In differentiating bladders (7, 10 days), rough endoplasmic reticulum, ribosomes, and alpha-glycogen were extensive in the epithelia, whereas concretions had disappeared. The apical surfaces of the epithelia were highly folded and lamellated, and lamellae were seen associated with fingerlike cytoplasmic projections (10 days) and spherical cytoplasmic bulges (15, 20 days). During maturation, SEM revealed nuclear profiles (20 days) and a muscular framework (30 days) in relief.