Histochemical Studies of Some Hydrolytic Enzymes in the Gregarine Digyalum oweni (Protozoa: Apicomplexa)

Summary: Histochemical methods for non-specific esterases, acid phosphatase and alkaline phosphatase have been applied to the gregarine Digyalum oweni , parasitic in the rectal region of the intestine of some Littorina species. Host intestines contain all three enzymes but only non-specific esterases are visualised in Digyalum , although no reactions occur in the nucleus and nucleolus or around the pouches of Digyalum . The apparent lack of positive reactions for acid and alkaline phosphatase in Digyalum is perhaps due to the impermeability of the epicyte of Digyalum ; other possibilities are discussed.