Argentophilic papillae of Schistosomatium douthitti cercariae (Trematoda: Schistosomatidae).

Argentophilic papillae of cercariae of Schistosomatium douthitti were studied by light microscopy. The basic number of body papillae was 56, excluding 20 at the anterior tip. The average number of tail papillae was 18. Average locations and spatial ranges of body papillae indicate a rather constant pattern. Tail papillae showed greater variability in location. Twenty papillae (10 on each side) at the anterior tip of cercariae were associated with gland duct openings. Two types of papillae were recognized with light microscopy--uniciliated bulbs and pits. The papilla pattern of S. douthitti differs from those of other species of schistosomes derived to date, and its constancy supports the usefulness of papillae in systematic studies.