Tegumentary papillae of Echinostoma caproni cercariae (Trematoda: Echinostomatidae).

Argentophilic staining and scanning electron microscopy were used to study the tegumentary papillae of Echinostoma caproni cercariae. The most abundant tegumentary papillae were uniciliate, but multiciliate papillae were also found, mainly on the ventral aspect of the oral collar. The distribution pattern of the papillae on the body and tail was in general similar to that seen in the cercariae of other 37-collar-spined Echinostoma species. Some differences were noted between E. caproni and the allopatric species, E. trivolvis. E. caproni has a greater number of papillae associated with the collar spines than does E. trivolvis. E. caproni has uniciliate papillae on the acetabulum, whereas E. trivolvis does not. Chaetotaxy is useful to distinguish subtle morphological differences in cercarial species in the 37-collar-spined Echinostoma complex.