Histochemical demonstration of aminopeptidase activity associated with the intramolluscan stages ofPhilophthalmus gralliMathis & Léger

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Abstract
Third-generation rediae and escaped cercariae ofPhilophthalmus gralliare found primarily in the interacinar spaces on the periphery of the hepatopancreas of its molluscan host,Tarebia granifera. The presence of these stages ofP. grallicauses both mechanical and physiological damage to the adjacent host cells. Mechanical damage results from ingestion by rediae and pressure exerted by motile rediae and cercariae. Histochemical tests involving two different substrates L-leucyl-α-naphthylamide and L-leucyl-4-methoxy-β-naphthylamide, have revealed the occurrence of aminopeptidase activity associated with the body surfaces of both rediae and cercariae. This exopeptidase is believed to be responsible for the lysis of the cytoplasm of surrounding host cells during migration and to be associated with extracaecal digestion. The intensity of the enzyme activity is correlated with the ages of the rediae and cercariae. Young rediae did not reveal aminopeptidase activity and cercariae within redial brood chambers revealed little or no activity.This research was supported in part by a grant from the American Cancer Society.

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