Report of a two-headed protoscolex of revealed by phase contrast microscopy in Shiraz, Iran.

sensu lato can produce cystic echinococcosis (CE)/hydatidosis in different hosts. Each CE cyst can produce numerous protoscoleces by its germinal layer in two forms: evaginated and invaginated. Usually, each protoscolex has one head consisting of a rostellum with two rows of hooks and four suckers. During a study of protoscolicidal agents on sheep protoscoleces, and investigations on their microscopic changes using Phase contrast microscopy, we observed a case of two- headed evaginated protoscolex. Two heads were attached to a unique bigger size of protoscolex body. Morphological observations showed its dimension around two times of usual protoscolex. There was no space between the bodies, hence one fused body was observed which was clearly shown by Phase contrast microscopy. Each head possessed two rows of hooks. Using micrometry all parts of the two-headed protoscolex, especially hooks were measured and photographed showing all aspects of its morphology including tegument, hooks, and two heads. Specific parts of two-headed protoscolex including suckers, hooks, also calcareous corpuscles were measured. The measurements on the two-headed protoscolex showed that the small hook blade length (SBL) and large hook blade length (LBL) were almost langer than one head protoscolex. A total of 120 calcareous corpuscles in two headed-protoscolex is much higher than one head protoscoleces.